MDEV-22456 Dropping the adaptive hash index may cause DDL to lock up InnoDB

If the InnoDB buffer pool contains many pages for a table or index
that is being dropped or rebuilt, and if many of such pages are
pointed to by the adaptive hash index, dropping the adaptive hash index
may consume a lot of time.

The time-consuming operation of dropping the adaptive hash index entries
is being executed while the InnoDB data dictionary cache dict_sys is
exclusively locked.

It is not actually necessary to drop all adaptive hash index entries
at the time a table or index is being dropped or rebuilt. We can let
the LRU replacement policy of the buffer pool take care of this gradually.
For this to work, we must detach the dict_table_t and dict_index_t
objects from the main dict_sys cache, and once the last
adaptive hash index entry for the detached table is removed
(when the garbage page is evicted from the buffer pool) we can free
the dict_table_t and dict_index_t object.

Related to this, in MDEV-16283, we made ALTER TABLE...DISCARD TABLESPACE
skip both the buffer pool eviction and the drop of the adaptive hash index.
We shifted the burden to ALTER TABLE...IMPORT TABLESPACE or DROP TABLE.
We can remove the eviction from DROP TABLE. We must retain the eviction
in the ALTER TABLE...IMPORT TABLESPACE code path, so that in case the
discarded table is being re-imported with the same tablespace identifier,
the fresh data from the imported tablespace will replace any stale pages
in the buffer pool.

rpl.rpl_failed_drop_tbl_binlog: Remove the test. DROP TABLE can
no longer be interrupted inside InnoDB.

fseg_free_page(), fseg_free_step(), fseg_free_step_not_header(),
fseg_free_page_low(), fseg_free_extent(): Remove the parameter
that specifies whether the adaptive hash index should be dropped.

btr_search_lazy_free(): Lazily free an index when the last
reference to it is dropped from the adaptive hash index.

buf_pool_clear_hash_index(): Declare static, and move to the
same compilation unit with the bulk of the adaptive hash index
code.

dict_index_t::clone(), dict_index_t::clone_if_needed():
Clone an index that is being rebuilt while adaptive hash index
entries exist. The original index will be inserted into
dict_table_t::freed_indexes and dict_index_t::set_freed()
will be called.

dict_index_t::set_freed(), dict_index_t::freed(): Note that
or check whether the index has been freed. We will use the
impossible page number 1 to denote this condition.

dict_index_t::n_ahi_pages(): Replaces btr_search_info_get_ref_count().

dict_index_t::detach_columns(): Move the assignment n_fields=0
to ha_innobase_inplace_ctx::clear_added_indexes().
We must have access to the columns when freeing the
adaptive hash index. Note: dict_table_t::v_cols[] will remain
valid. If virtual columns are dropped or added, the table
definition will be reloaded in ha_innobase::commit_inplace_alter_table().

buf_page_mtr_lock(): Drop a stale adaptive hash index if needed.

We will also reduce the number of btr_get_search_latch() calls
and enclose some more code inside #ifdef BTR_CUR_HASH_ADAPT
in order to benefit cmake -DWITH_INNODB_AHI=OFF.

34 files changed, 552 insertions, 903 deletions

diff --git a/mysql-test/suite/rpl/r/rpl_failed_drop_tbl_binlog.result b/mysql-test/suite/rpl/r/rpl_failed_drop_tbl_binlog.result
deleted file mode 100644
index df36fa82e0f..00000000000
--- a/mysql-test/suite/rpl/r/rpl_failed_drop_tbl_binlog.result
+++ /dev/null
@@ -1,32 +0,0 @@
-include/master-slave.inc
-[connection master]
-create table t1 (a int) engine=innodb;
-create table t2 (b longblob) engine=innodb;
-create table t3 (c int) engine=innodb;
-insert into t2 values (repeat('b',1024*1024));
-insert into t2 select * from t2;
-insert into t2 select * from t2;
-insert into t2 select * from t2;
-insert into t2 select * from t2;
-set debug_sync='rm_table_no_locks_before_delete_table SIGNAL nogo WAIT_FOR go EXECUTE 2';
-drop table t1, t2, t3;
-connect foo,localhost,root;
-set debug_sync='now SIGNAL go';
-kill query CONNECTION_ID;
-connection master;
-ERROR 70100: Query execution was interrupted
-"Tables t2 and t3 should be listed"
-SHOW TABLES;
-Tables_in_test
-t2
-t3
-include/show_binlog_events.inc
-Log_name	Pos	Event_type	Server_id	End_log_pos	Info
-master-bin.000001	#	Gtid	#	#	GTID #-#-#
-master-bin.000001	#	Query	#	#	use `test`; DROP TABLE `t1` /* generated by server */
-connection slave;
-drop table t2, t3;
-connection master;
-set debug_sync='RESET';
-drop table t2, t3;
-include/rpl_end.inc
diff --git a/mysql-test/suite/rpl/t/rpl_failed_drop_tbl_binlog.test b/mysql-test/suite/rpl/t/rpl_failed_drop_tbl_binlog.test
deleted file mode 100644
index 281e2a2ab47..00000000000
--- a/mysql-test/suite/rpl/t/rpl_failed_drop_tbl_binlog.test
+++ /dev/null
@@ -1,64 +0,0 @@
-# ==== Purpose ====
-#
-# Check that when the execution of a DROP TABLE command with single table
-# fails it should not be written to the binary log. Also test that when the
-# execution of DROP TABLE command with multiple tables fails the command
-# should be written into the binary log.
-#
-# ==== Implementation ====
-#
-# Steps:
-#    0 - Create tables named t1, t2, t3
-#    1 - Execute DROP TABLE t1,t2,t3 command.
-#    2 - Kill the DROP TABLE command while it is trying to drop table 't2'.
-#    3 - Verify that tables t2,t3 are present after the DROP command execution
-#        was interrupted.
-#    4 - Check that table 't1' is present in binary log as part of DROP
-#        command.
-#
-# ==== References ====
-#
-# MDEV-20348: DROP TABLE IF EXISTS killed on master but was replicated.
-#
-
---source include/have_innodb.inc
---source include/have_debug_sync.inc
---source include/have_binlog_format_statement.inc
---source include/master-slave.inc
-
-create table t1 (a int) engine=innodb;
-create table t2 (b longblob) engine=innodb;
-create table t3 (c int) engine=innodb;
-insert into t2 values (repeat('b',1024*1024));
-insert into t2 select * from t2;
-insert into t2 select * from t2;
-insert into t2 select * from t2;
-insert into t2 select * from t2;
-let $binlog_start= query_get_value(SHOW MASTER STATUS, Position, 1);
-
-let $id=`select connection_id()`;
-set debug_sync='rm_table_no_locks_before_delete_table SIGNAL nogo WAIT_FOR go EXECUTE 2';
-send drop table t1, t2, t3;
-
-connect foo,localhost,root;
-set debug_sync='now SIGNAL go';
-let $wait_condition=select 1 from information_schema.processlist where state like 'debug sync point:%';
-source include/wait_condition.inc;
---replace_result $id CONNECTION_ID
-eval kill query $id;
-
-connection master;
-error ER_QUERY_INTERRUPTED;
-reap;
-
---echo "Tables t2 and t3 should be listed"
-SHOW TABLES;
---source include/show_binlog_events.inc
---sync_slave_with_master
-drop table t2, t3;
-
-connection master;
-set debug_sync='RESET';
-drop table t2, t3;
-
-source include/rpl_end.inc;
diff --git a/storage/innobase/btr/btr0btr.cc b/storage/innobase/btr/btr0btr.cc
index 2049bbd26fa..5f38e623985 100644
--- a/storage/innobase/btr/btr0btr.cc
+++ b/storage/innobase/btr/btr0btr.cc
@@ -2,7 +2,7 @@
 
 Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
-Copyright (c) 2014, 2019, MariaDB Corporation.
+Copyright (c) 2014, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -723,8 +723,10 @@ void btr_page_free(dict_index_t* index, buf_block_t* block, mtr_t* mtr,
 {
 	ut_ad(mtr_is_block_fix(mtr, block, MTR_MEMO_PAGE_X_FIX, index->table));
 #ifdef BTR_CUR_HASH_ADAPT
-	ut_ad(!block->index || !blob);
-	ut_ad(!block->index || page_is_leaf(block->frame));
+	if (block->index && !block->index->freed()) {
+		ut_ad(!blob);
+		ut_ad(page_is_leaf(block->frame));
+	}
 #endif
 	ut_ad(index->space == block->page.id.space());
 	/* The root page is freed by btr_free_root(). */
@@ -751,7 +753,7 @@ void btr_page_free(dict_index_t* index, buf_block_t* block, mtr_t* mtr,
 	fseg_free_page(seg_header,
 		       block->page.id.space(),
 		       block->page.id.page_no(),
-		       block->index != NULL, mtr);
+		       mtr);
 
 	/* The page was marked free in the allocation bitmap, but it
 	should remain exclusively latched until mtr_t::commit() or until it
@@ -876,7 +878,7 @@ btr_page_get_father_node_ptr_func(
 	err = btr_cur_search_to_nth_level(
 		index, level + 1, tuple,
 		PAGE_CUR_LE, latch_mode, cursor, 0,
-		file, line, mtr);
+		file, line, mtr, 0);
 
 	if (err != DB_SUCCESS) {
 		ib::warn() << " Error code: " << err
@@ -1005,7 +1007,7 @@ static void btr_free_root(buf_block_t* block, mtr_t* mtr, bool invalidate)
 			BTR_FREED_INDEX_ID, mtr);
 	}
 
-	while (!fseg_free_step(header, true, mtr)) {
+	while (!fseg_free_step(header, mtr)) {
 		/* Free the entire segment in small steps. */
 	}
 }
@@ -1254,7 +1256,7 @@ leaf_loop:
 	fsp0fsp. */
 
 	finished = fseg_free_step(root + PAGE_HEADER + PAGE_BTR_SEG_LEAF,
-				  true, &mtr);
+				  &mtr);
 	mtr_commit(&mtr);
 
 	if (!finished) {
@@ -1274,7 +1276,7 @@ top_loop:
 #endif /* UNIV_BTR_DEBUG */
 
 	finished = fseg_free_step_not_header(
-		root + PAGE_HEADER + PAGE_BTR_SEG_TOP, true, &mtr);
+		root + PAGE_HEADER + PAGE_BTR_SEG_TOP, &mtr);
 	mtr_commit(&mtr);
 
 	if (!finished) {
@@ -2342,7 +2344,7 @@ btr_insert_on_non_leaf_level_func(
 		dberr_t err = btr_cur_search_to_nth_level(
 			index, level, tuple, PAGE_CUR_LE,
 			BTR_CONT_MODIFY_TREE,
-			&cursor, 0, file, line, mtr);
+			&cursor, 0, file, line, mtr, 0);
 
 		if (err != DB_SUCCESS) {
 			ib::warn() << " Error code: " << err
@@ -2363,7 +2365,7 @@ btr_insert_on_non_leaf_level_func(
 		btr_cur_search_to_nth_level(index, level, tuple,
 					    PAGE_CUR_RTREE_INSERT,
 					    BTR_CONT_MODIFY_TREE,
-					    &cursor, 0, file, line, mtr);
+					    &cursor, 0, file, line, mtr, 0);
 	}
 
 	ut_ad(cursor.flag == BTR_CUR_BINARY);
diff --git a/storage/innobase/btr/btr0cur.cc b/storage/innobase/btr/btr0cur.cc
index 2bf657f037f..37ba133cb0f 100644
--- a/storage/innobase/btr/btr0cur.cc
+++ b/storage/innobase/btr/btr0cur.cc
@@ -864,8 +864,7 @@ search tuple should be performed in the B-tree. InnoDB does an insert
 immediately after the cursor. Thus, the cursor may end up on a user record,
 or on a page infimum record. */
 dberr_t
-btr_cur_search_to_nth_level(
-/*========================*/
+btr_cur_search_to_nth_level_func(
 	dict_index_t*	index,	/*!< in: index */
 	ulint		level,	/*!< in: the tree level of search */
 	const dtuple_t*	tuple,	/*!< in: data tuple; NOTE: n_fields_cmp in
@@ -887,10 +886,12 @@ btr_cur_search_to_nth_level(
 				to protect the record! */
 	btr_cur_t*	cursor, /*!< in/out: tree cursor; the cursor page is
 				s- or x-latched, but see also above! */
+#ifdef BTR_CUR_HASH_ADAPT
 	ulint		has_search_latch,
 				/*!< in: info on the latch mode the
 				caller currently has on search system:
 				RW_S_LATCH, or 0 */
+#endif /* BTR_CUR_HASH_ADAPT */
 	const char*	file,	/*!< in: file name */
 	unsigned	line,	/*!< in: line where called */
 	mtr_t*		mtr,	/*!< in: mtr */
@@ -1053,6 +1054,7 @@ btr_cur_search_to_nth_level(
 	}
 
 #ifdef BTR_CUR_HASH_ADAPT
+	rw_lock_t* const search_latch = btr_get_search_latch(index);
 
 # ifdef UNIV_SEARCH_PERF_STAT
 	info->n_searches++;
@@ -1073,8 +1075,7 @@ btr_cur_search_to_nth_level(
 	    will have to check it again. */
 	    && btr_search_enabled
 	    && !modify_external
-	    && rw_lock_get_writer(btr_get_search_latch(index))
-	    == RW_LOCK_NOT_LOCKED
+	    && rw_lock_get_writer(search_latch) == RW_LOCK_NOT_LOCKED
 	    && btr_search_guess_on_hash(index, info, tuple, mode,
 					latch_mode, cursor,
 					has_search_latch, mtr)) {
@@ -1098,10 +1099,12 @@ btr_cur_search_to_nth_level(
 	/* If the hash search did not succeed, do binary search down the
 	tree */
 
+#ifdef BTR_CUR_HASH_ADAPT
 	if (has_search_latch) {
 		/* Release possible search latch to obey latching order */
-		btr_search_s_unlock(index);
+		rw_lock_s_unlock(search_latch);
 	}
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	/* Store the position of the tree latch we push to mtr so that we
 	know how to release it when we have latched leaf node(s) */
@@ -2155,9 +2158,11 @@ func_exit:
 		ut_free(prev_tree_savepoints);
 	}
 
+#ifdef BTR_CUR_HASH_ADAPT
 	if (has_search_latch) {
-		btr_search_s_lock(index);
+		rw_lock_s_lock(search_latch);
 	}
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	if (mbr_adj) {
 		/* remember that we will need to adjust parent MBR */
@@ -5746,7 +5751,7 @@ btr_estimate_n_rows_in_range_low(
 		btr_cur_search_to_nth_level(index, 0, tuple1, mode1,
 					    BTR_SEARCH_LEAF | BTR_ESTIMATE,
 					    &cursor, 0,
-					    __FILE__, __LINE__, &mtr);
+					    __FILE__, __LINE__, &mtr, 0);
 
 		ut_ad(!page_rec_is_infimum(btr_cur_get_rec(&cursor)));
 
@@ -5800,7 +5805,7 @@ btr_estimate_n_rows_in_range_low(
 		btr_cur_search_to_nth_level(index, 0, tuple2, mode2,
 					    BTR_SEARCH_LEAF | BTR_ESTIMATE,
 					    &cursor, 0,
-					    __FILE__, __LINE__, &mtr);
+					    __FILE__, __LINE__, &mtr, 0);
 
 		const rec_t*	rec = btr_cur_get_rec(&cursor);
 
diff --git a/storage/innobase/btr/btr0pcur.cc b/storage/innobase/btr/btr0pcur.cc
index 7a62e4c128a..4340c2f32b0 100644
--- a/storage/innobase/btr/btr0pcur.cc
+++ b/storage/innobase/btr/btr0pcur.cc
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2016, 2019, MariaDB Corporation.
+Copyright (c) 2016, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -353,8 +353,11 @@ btr_pcur_restore_position_func(
 		mode = PAGE_CUR_UNSUPP;
 	}
 
-	btr_pcur_open_with_no_init_func(index, tuple, mode, latch_mode,
-					cursor, 0, file, line, mtr);
+	btr_pcur_open_with_no_init_func(index, tuple, mode, latch_mode, cursor,
+#ifdef BTR_CUR_HASH_ADAPT
+					0,
+#endif /* BTR_CUR_HASH_ADAPT */
+					file, line, mtr);
 
 	/* Restore the old search mode */
 	cursor->search_mode = old_mode;
diff --git a/storage/innobase/btr/btr0sea.cc b/storage/innobase/btr/btr0sea.cc
index 7671895953e..f1075358ad2 100644
--- a/storage/innobase/btr/btr0sea.cc
+++ b/storage/innobase/btr/btr0sea.cc
@@ -2,7 +2,7 @@
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2008, Google Inc.
-Copyright (c) 2017, 2019, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -141,15 +141,8 @@ static
 void
 btr_search_check_free_space_in_heap(dict_index_t* index)
 {
-	hash_table_t*	table;
-	mem_heap_t*	heap;
-
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_S));
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_X));
-
-	table = btr_get_search_table(index);
-
-	heap = table->heap;
+	hash_table_t* table = btr_get_search_table(index);
+	mem_heap_t* heap = table->heap;
 
 	/* Note that we peek the value of heap->free_block without reserving
 	the latch: this is ok, because we will not guarantee that there will
@@ -157,8 +150,9 @@ btr_search_check_free_space_in_heap(dict_index_t* index)
 
 	if (heap->free_block == NULL) {
 		buf_block_t*	block = buf_block_alloc(NULL);
+		rw_lock_t*	latch = btr_get_search_latch(index);
 
-		btr_search_x_lock(index);
+		rw_lock_x_lock(latch);
 
 		if (btr_search_enabled
 		    && heap->free_block == NULL) {
@@ -167,7 +161,7 @@ btr_search_check_free_space_in_heap(dict_index_t* index)
 			buf_block_free(block);
 		}
 
-		btr_search_x_unlock(index);
+		rw_lock_x_unlock(latch);
 	}
 }
 
@@ -289,18 +283,88 @@ btr_search_disable_ref_count(
 {
 	dict_index_t*	index;
 
-	ut_ad(mutex_own(&dict_sys->mutex));
-
 	for (index = dict_table_get_first_index(table);
 	     index != NULL;
 	     index = dict_table_get_next_index(index)) {
-
-		ut_ad(rw_lock_own(btr_get_search_latch(index), RW_LOCK_X));
-
 		index->search_info->ref_count = 0;
 	}
 }
 
+/** Lazily free detached metadata when removing the last reference. */
+ATTRIBUTE_COLD static void btr_search_lazy_free(dict_index_t *index)
+{
+  ut_ad(index->freed());
+  dict_table_t *table= index->table;
+  /* Perform the skipped steps of dict_index_remove_from_cache_low(). */
+  UT_LIST_REMOVE(table->freed_indexes, index);
+  rw_lock_free(&index->lock);
+  dict_mem_index_free(index);
+
+  if (!UT_LIST_GET_LEN(table->freed_indexes) &&
+      !UT_LIST_GET_LEN(table->indexes))
+  {
+    ut_ad(table->id == 0);
+    dict_mem_table_free(table);
+  }
+}
+
+/** Clear the adaptive hash index on all pages in the buffer pool. */
+static void buf_pool_clear_hash_index()
+{
+  ut_ad(btr_search_own_all(RW_LOCK_X));
+  ut_ad(!btr_search_enabled);
+
+  std::set<dict_index_t*> garbage;
+
+  for (ulong p = 0; p < srv_buf_pool_instances; p++)
+  {
+    buf_pool_t *buf_pool= buf_pool_from_array(p);
+    buf_chunk_t *chunks= buf_pool->chunks;
+    buf_chunk_t *chunk= chunks + buf_pool->n_chunks;
+
+    while (--chunk >= chunks)
+    {
+      buf_block_t *block= chunk->blocks;
+      for (ulint i= chunk->size; i--; block++)
+      {
+        dict_index_t *index= block->index;
+        assert_block_ahi_valid(block);
+
+        /* We can clear block->index and block->n_pointers when
+        btr_search_own_all(RW_LOCK_X); see the comments in buf0buf.h */
+
+        if (!index)
+        {
+# if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
+          ut_a(!block->n_pointers);
+# endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
+          continue;
+        }
+
+        ut_d(buf_page_state state= buf_block_get_state(block));
+        /* Another thread may have set the state to
+        BUF_BLOCK_REMOVE_HASH in buf_LRU_block_remove_hashed().
+
+        The state change in buf_page_realloc() is not observable here,
+        because in that case we would have !block->index.
+
+        In the end, the entire adaptive hash index will be removed. */
+        ut_ad(state == BUF_BLOCK_FILE_PAGE || state == BUF_BLOCK_REMOVE_HASH);
+# if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
+        block->n_pointers= 0;
+# endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
+        if (index->freed())
+          garbage.insert(index);
+        block->index= NULL;
+      }
+    }
+  }
+
+  for (std::set<dict_index_t*>::iterator i= garbage.begin();
+       i != garbage.end(); i++)
+    btr_search_lazy_free(*i);
+}
+
 /** Disable the adaptive hash search system and empty the index.
 @param[in]	need_mutex	need to acquire dict_sys->mutex */
 void
@@ -373,33 +437,6 @@ btr_search_enable()
 	btr_search_x_unlock_all();
 }
 
-/** Returns the value of ref_count. The value is protected by latch.
-@param[in]	info		search info
-@param[in]	index		index identifier
-@return ref_count value. */
-ulint
-btr_search_info_get_ref_count(
-	btr_search_t*	info,
-	dict_index_t*	index)
-{
-	ulint ret = 0;
-
-	if (!btr_search_enabled) {
-		return(ret);
-	}
-
-	ut_ad(info);
-
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_S));
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_X));
-
-	btr_search_s_lock(index);
-	ret = info->ref_count;
-	btr_search_s_unlock(index);
-
-	return(ret);
-}
-
 /** Updates the search info of an index about hash successes. NOTE that info
 is NOT protected by any semaphore, to save CPU time! Do not assume its fields
 are consistent.
@@ -415,8 +452,8 @@ btr_search_info_update_hash(
 	ulint		n_unique;
 	int		cmp;
 
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_S));
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_X));
+	ut_ad(!rw_lock_own_flagged(btr_get_search_latch(index),
+				   RW_LOCK_FLAG_X | RW_LOCK_FLAG_S));
 
 	if (dict_index_is_ibuf(index)) {
 		/* So many deletes are performed on an insert buffer tree
@@ -601,28 +638,25 @@ btr_search_update_hash_ref(
 	buf_block_t*		block,
 	const btr_cur_t*	cursor)
 {
-	dict_index_t*	index;
-	ulint		fold;
-	rec_t*		rec;
-
 	ut_ad(cursor->flag == BTR_CUR_HASH_FAIL);
-	ut_ad(rw_lock_own(btr_get_search_latch(cursor->index), RW_LOCK_X));
+
 	ut_ad(rw_lock_own_flagged(&block->lock,
 				  RW_LOCK_FLAG_X | RW_LOCK_FLAG_S));
 	ut_ad(page_align(btr_cur_get_rec(cursor)) == block->frame);
 	ut_ad(page_is_leaf(block->frame));
 	assert_block_ahi_valid(block);
 
-	index = block->index;
+	dict_index_t* index = block->index;
 
 	if (!index) {
-
 		return;
 	}
 
 	ut_ad(block->page.id.space() == index->space);
 	ut_a(index == cursor->index);
-	ut_a(!dict_index_is_ibuf(index));
+	ut_ad(!dict_index_is_ibuf(index));
+	rw_lock_t* const latch = btr_get_search_latch(index);
+	rw_lock_x_lock(latch);
 
 	if ((info->n_hash_potential > 0)
 	    && (block->curr_n_fields == info->n_fields)
@@ -632,28 +666,30 @@ btr_search_update_hash_ref(
 		rec_offs	offsets_[REC_OFFS_NORMAL_SIZE];
 		rec_offs_init(offsets_);
 
-		rec = btr_cur_get_rec(cursor);
+		const rec_t* rec = btr_cur_get_rec(cursor);
 
 		if (!page_rec_is_user_rec(rec)) {
-
-			return;
+			goto func_exit;
 		}
 
-		fold = rec_fold(rec,
-				rec_get_offsets(rec, index, offsets_, true,
-						ULINT_UNDEFINED, &heap),
-				block->curr_n_fields,
-				block->curr_n_bytes, index->id);
+		ulint fold = rec_fold(
+			rec,
+			rec_get_offsets(rec, index, offsets_, true,
+					ULINT_UNDEFINED, &heap),
+			block->curr_n_fields,
+			block->curr_n_bytes, index->id);
 		if (UNIV_LIKELY_NULL(heap)) {
 			mem_heap_free(heap);
 		}
-		ut_ad(rw_lock_own(btr_get_search_latch(index), RW_LOCK_X));
 
 		ha_insert_for_fold(btr_get_search_table(index), fold,
 				   block, rec);
 
 		MONITOR_INC(MONITOR_ADAPTIVE_HASH_ROW_ADDED);
 	}
+
+func_exit:
+	rw_lock_x_unlock(latch);
 }
 
 /** Updates the search info.
@@ -692,12 +728,7 @@ btr_search_info_update_slow(
 #ifdef UNIV_SEARCH_PERF_STAT
 		btr_search_n_hash_fail++;
 #endif /* UNIV_SEARCH_PERF_STAT */
-
-		btr_search_x_lock(cursor->index);
-
 		btr_search_update_hash_ref(info, block, cursor);
-
-		btr_search_x_unlock(cursor->index);
 	}
 
 	if (build_index) {
@@ -898,7 +929,6 @@ btr_search_guess_on_hash(
 	ulint		has_search_latch,
 	mtr_t*		mtr)
 {
-	const rec_t*	rec;
 	ulint		fold;
 	index_id_t	index_id;
 #ifdef notdefined
@@ -944,33 +974,28 @@ btr_search_guess_on_hash(
 	cursor->fold = fold;
 	cursor->flag = BTR_CUR_HASH;
 
+	rw_lock_t* const latch = btr_get_search_latch(index);
+
 	if (!has_search_latch) {
-		btr_search_s_lock(index);
+		rw_lock_s_lock(latch);
 
 		if (!btr_search_enabled) {
-			btr_search_s_unlock(index);
-
+fail:
+			if (!has_search_latch) {
+				rw_lock_s_unlock(latch);
+			}
 			btr_search_failure(info, cursor);
-
 			return(FALSE);
 		}
 	}
 
-	ut_ad(rw_lock_get_writer(btr_get_search_latch(index)) != RW_LOCK_X);
-	ut_ad(rw_lock_get_reader_count(btr_get_search_latch(index)) > 0);
-
-	rec = (rec_t*) ha_search_and_get_data(
-			btr_get_search_table(index), fold);
+	ut_ad(rw_lock_own(latch, RW_LOCK_S));
 
-	if (rec == NULL) {
+	const rec_t* rec = static_cast<const rec_t*>(
+		ha_search_and_get_data(btr_get_search_table(index), fold));
 
-		if (!has_search_latch) {
-			btr_search_s_unlock(index);
-		}
-
-		btr_search_failure(info, cursor);
-
-		return(FALSE);
+	if (!rec) {
+		goto fail;
 	}
 
 	buf_block_t*	block = buf_block_from_ahi(rec);
@@ -980,32 +1005,34 @@ btr_search_guess_on_hash(
 		if (!buf_page_get_known_nowait(
 			latch_mode, block, BUF_MAKE_YOUNG,
 			__FILE__, __LINE__, mtr)) {
-
-			if (!has_search_latch) {
-				btr_search_s_unlock(index);
-			}
-
-			btr_search_failure(info, cursor);
-
-			return(FALSE);
+			goto fail;
 		}
 
-		btr_search_s_unlock(index);
+		const bool fail = index != block->index
+			&& index_id == block->index->id;
+		ut_a(!fail || block->index->freed());
+		rw_lock_s_unlock(latch);
 
 		buf_block_dbg_add_level(block, SYNC_TREE_NODE_FROM_HASH);
+		if (UNIV_UNLIKELY(fail)) {
+			btr_search_drop_page_hash_index(block);
+			goto fail_and_release_page;
+		}
+	} else if (UNIV_UNLIKELY(index != block->index
+				 && index_id == block->index->id)) {
+		ut_a(block->index->freed());
+		goto fail_and_release_page;
 	}
 
 	if (buf_block_get_state(block) != BUF_BLOCK_FILE_PAGE) {
 
 		ut_ad(buf_block_get_state(block) == BUF_BLOCK_REMOVE_HASH);
-
+fail_and_release_page:
 		if (!has_search_latch) {
-
 			btr_leaf_page_release(block, latch_mode, mtr);
 		}
 
 		btr_search_failure(info, cursor);
-
 		return(FALSE);
 	}
 
@@ -1024,14 +1051,7 @@ btr_search_guess_on_hash(
 	    || !btr_search_check_guess(cursor,
 				       has_search_latch,
 				       tuple, mode, mtr)) {
-
-		if (!has_search_latch) {
-			btr_leaf_page_release(block, latch_mode, mtr);
-		}
-
-		btr_search_failure(info, cursor);
-
-		return(FALSE);
+		goto fail_and_release_page;
 	}
 
 	if (info->n_hash_potential < BTR_SEARCH_BUILD_LIMIT + 5) {
@@ -1115,30 +1135,26 @@ btr_search_drop_page_hash_index(buf_block_t* block)
 	ulint*			folds;
 	ulint			i;
 	mem_heap_t*		heap;
-	const dict_index_t*	index;
 	rec_offs*		offsets;
 	rw_lock_t*		latch;
-	btr_search_t*		info;
 
 retry:
-	/* Do a dirty check on block->index, return if the block is
-	not in the adaptive hash index. */
-	index = block->index;
 	/* This debug check uses a dirty read that could theoretically cause
 	false positives while buf_pool_clear_hash_index() is executing. */
 	assert_block_ahi_valid(block);
 
-	if (index == NULL) {
+	if (!block->index) {
 		return;
 	}
 
 	ut_ad(block->page.buf_fix_count == 0
 	      || buf_block_get_state(block) == BUF_BLOCK_REMOVE_HASH
 	      || rw_lock_own_flagged(&block->lock,
-				     RW_LOCK_FLAG_X | RW_LOCK_FLAG_S));
+				     RW_LOCK_FLAG_X | RW_LOCK_FLAG_S
+				     | RW_LOCK_FLAG_SX));
 	ut_ad(page_is_leaf(block->frame));
 
-	/* We must not dereference index here, because it could be freed
+	/* We must not dereference block->index here, because it could be freed
 	if (index->table->n_ref_count == 0 && !mutex_own(&dict_sys->mutex)).
 	Determine the ahi_slot based on the block contents. */
 
@@ -1156,18 +1172,12 @@ retry:
 	rw_lock_s_lock(latch);
 	assert_block_ahi_valid(block);
 
-	if (block->index == NULL) {
+	if (!block->index) {
 		rw_lock_s_unlock(latch);
 		return;
 	}
 
-	/* The index associated with a block must remain the
-	same, because we are holding block->lock or the block is
-	not accessible by other threads (BUF_BLOCK_REMOVE_HASH),
-	or the index is not accessible to other threads
-	(buf_fix_count == 0 when DROP TABLE or similar is executing
-	buf_LRU_drop_page_hash_for_tablespace()). */
-	ut_a(index == block->index);
+	dict_index_t* index = block->index;
 #ifdef MYSQL_INDEX_DISABLE_AHI
 	ut_ad(!index->disable_ahi);
 #endif
@@ -1176,7 +1186,7 @@ retry:
 	ut_ad(index->space == FIL_NULL
 	      || block->page.id.space() == index->space);
 	ut_a(index_id == index->id);
-	ut_a(!dict_index_is_ibuf(index));
+	ut_ad(!dict_index_is_ibuf(index));
 #ifdef UNIV_DEBUG
 	switch (dict_index_get_online_status(index)) {
 	case ONLINE_INDEX_CREATION:
@@ -1281,9 +1291,14 @@ next_rec:
 			folds[i], page);
 	}
 
-	info = btr_search_get_info(block->index);
-	ut_a(info->ref_count > 0);
-	info->ref_count--;
+	switch (index->search_info->ref_count--) {
+	case 0:
+		ut_error;
+	case 1:
+		if (index->freed()) {
+			btr_search_lazy_free(index);
+		}
+	}
 
 	block->index = NULL;
 
@@ -1383,27 +1398,27 @@ btr_search_build_page_hash_index(
 	rec_offs_init(offsets_);
 	ut_ad(index);
 	ut_ad(block->page.id.space() == index->space);
-	ut_a(!dict_index_is_ibuf(index));
+	ut_ad(!dict_index_is_ibuf(index));
 	ut_ad(page_is_leaf(block->frame));
 
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_X));
 	ut_ad(rw_lock_own_flagged(&block->lock,
 				  RW_LOCK_FLAG_X | RW_LOCK_FLAG_S));
+	ut_ad(block->page.id.page_no() >= 3);
 
-	btr_search_s_lock(index);
+	rw_lock_t* const latch = btr_get_search_latch(index);
+	rw_lock_s_lock(latch);
 
 	table = btr_get_search_table(index);
 	page = buf_block_get_frame(block);
 
-	if (block->index && ((block->curr_n_fields != n_fields)
-			     || (block->curr_n_bytes != n_bytes)
-			     || (block->curr_left_side != left_side))) {
-
-		btr_search_s_unlock(index);
+	const bool must_drop = block->index
+		&& ((block->curr_n_fields != n_fields)
+		    || (block->curr_n_bytes != n_bytes)
+		    || (block->curr_left_side != left_side));
+	rw_lock_s_unlock(latch);
 
+	if (must_drop) {
 		btr_search_drop_page_hash_index(block);
-	} else {
-		btr_search_s_unlock(index);
 	}
 
 	/* Check that the values for hash index build are sensible */
@@ -1495,7 +1510,7 @@ btr_search_build_page_hash_index(
 
 	btr_search_check_free_space_in_heap(index);
 
-	btr_search_x_lock(index);
+	rw_lock_x_lock(latch);
 
 	if (!btr_search_enabled) {
 		goto exit_func;
@@ -1533,7 +1548,7 @@ btr_search_build_page_hash_index(
 	MONITOR_INC_VALUE(MONITOR_ADAPTIVE_HASH_ROW_ADDED, n_cached);
 exit_func:
 	assert_block_ahi_valid(block);
-	btr_search_x_unlock(index);
+	rw_lock_x_unlock(latch);
 
 	ut_free(folds);
 	ut_free(recs);
@@ -1566,21 +1581,19 @@ btr_search_move_or_delete_hash_entries(
 	ut_ad(rw_lock_own(&(block->lock), RW_LOCK_X));
 	ut_ad(rw_lock_own(&(new_block->lock), RW_LOCK_X));
 
-	btr_search_s_lock(index);
+	rw_lock_t* const latch = btr_get_search_latch(index);
+	rw_lock_s_lock(latch);
 
 	ut_a(!new_block->index || new_block->index == index);
 	ut_a(!block->index || block->index == index);
-	ut_a(!(new_block->index || block->index)
-	     || !dict_index_is_ibuf(index));
+	ut_ad(!(new_block->index || block->index)
+	      || !dict_index_is_ibuf(index));
 	assert_block_ahi_valid(block);
 	assert_block_ahi_valid(new_block);
 
 	if (new_block->index) {
-
-		btr_search_s_unlock(index);
-
+		rw_lock_s_unlock(latch);
 		btr_search_drop_page_hash_index(block);
-
 		return;
 	}
 
@@ -1593,7 +1606,7 @@ btr_search_move_or_delete_hash_entries(
 		new_block->n_bytes = block->curr_n_bytes;
 		new_block->left_side = left_side;
 
-		btr_search_s_unlock(index);
+		rw_lock_s_unlock(latch);
 
 		ut_a(n_fields > 0 || n_bytes > 0);
 
@@ -1605,7 +1618,7 @@ btr_search_move_or_delete_hash_entries(
 		return;
 	}
 
-	btr_search_s_unlock(index);
+	rw_lock_s_unlock(latch);
 }
 
 /** Updates the page hash index when a single record is deleted from a page.
@@ -1647,7 +1660,7 @@ btr_search_update_hash_on_delete(btr_cur_t* cursor)
 	ut_ad(block->page.id.space() == index->space);
 	ut_a(index == cursor->index);
 	ut_a(block->curr_n_fields > 0 || block->curr_n_bytes > 0);
-	ut_a(!dict_index_is_ibuf(index));
+	ut_ad(!dict_index_is_ibuf(index));
 
 	table = btr_get_search_table(index);
 
@@ -1660,7 +1673,8 @@ btr_search_update_hash_on_delete(btr_cur_t* cursor)
 		mem_heap_free(heap);
 	}
 
-	btr_search_x_lock(index);
+	rw_lock_t* const latch = btr_get_search_latch(index);
+	rw_lock_x_lock(latch);
 	assert_block_ahi_valid(block);
 
 	if (block->index) {
@@ -1676,7 +1690,7 @@ btr_search_update_hash_on_delete(btr_cur_t* cursor)
 		assert_block_ahi_valid(block);
 	}
 
-	btr_search_x_unlock(index);
+	rw_lock_x_unlock(latch);
 }
 
 /** Updates the page hash index when a single record is inserted on a page.
@@ -1712,9 +1726,10 @@ btr_search_update_hash_node_on_insert(btr_cur_t* cursor)
 	}
 
 	ut_a(cursor->index == index);
-	ut_a(!dict_index_is_ibuf(index));
+	ut_ad(!dict_index_is_ibuf(index));
 
-	btr_search_x_lock(index);
+	rw_lock_t* const latch = btr_get_search_latch(index);
+	rw_lock_x_lock(latch);
 
 	if (!block->index) {
 
@@ -1738,10 +1753,9 @@ btr_search_update_hash_node_on_insert(btr_cur_t* cursor)
 
 func_exit:
 		assert_block_ahi_valid(block);
-		btr_search_x_unlock(index);
+		rw_lock_x_unlock(latch);
 	} else {
-		btr_search_x_unlock(index);
-
+		rw_lock_x_unlock(latch);
 		btr_search_update_hash_on_insert(cursor);
 	}
 }
@@ -1765,8 +1779,6 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 	ulint		next_fold = 0; /* remove warning (??? bug ???) */
 	ulint		n_fields;
 	ulint		n_bytes;
-	ibool		left_side;
-	ibool		locked		= FALSE;
 	mem_heap_t*	heap		= NULL;
 	rec_offs	offsets_[REC_OFFS_NORMAL_SIZE];
 	rec_offs*	offsets		= offsets_;
@@ -1803,11 +1815,11 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 	ut_a(!index->disable_ahi);
 #endif
 	ut_a(index == cursor->index);
-	ut_a(!dict_index_is_ibuf(index));
+	ut_ad(!dict_index_is_ibuf(index));
 
 	n_fields = block->curr_n_fields;
 	n_bytes = block->curr_n_bytes;
-	left_side = block->curr_left_side;
+	const bool left_side = block->curr_left_side;
 
 	ins_rec = page_rec_get_next_const(rec);
 	next_rec = page_rec_get_next_const(ins_rec);
@@ -1824,17 +1836,18 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 				     n_bytes, index->id);
 	}
 
+	rw_lock_t* const latch = btr_get_search_latch(index);
+	bool locked = false;
+
 	if (!page_rec_is_infimum(rec)) {
 		offsets = rec_get_offsets(
 			rec, index, offsets, true,
 			btr_search_get_n_fields(n_fields, n_bytes), &heap);
 		fold = rec_fold(rec, offsets, n_fields, n_bytes, index->id);
 	} else {
-		if (left_side) {
-
-			btr_search_x_lock(index);
-
-			locked = TRUE;
+		locked = left_side;
+		if (locked) {
+			rw_lock_x_lock(latch);
 
 			if (!btr_search_enabled) {
 				goto function_exit;
@@ -1849,10 +1862,8 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 	if (fold != ins_fold) {
 
 		if (!locked) {
-
-			btr_search_x_lock(index);
-
-			locked = TRUE;
+			locked = true;
+			rw_lock_x_lock(latch);
 
 			if (!btr_search_enabled) {
 				goto function_exit;
@@ -1870,11 +1881,9 @@ check_next_rec:
 	if (page_rec_is_supremum(next_rec)) {
 
 		if (!left_side) {
-
 			if (!locked) {
-				btr_search_x_lock(index);
-
-				locked = TRUE;
+				locked = true;
+				rw_lock_x_lock(latch);
 
 				if (!btr_search_enabled) {
 					goto function_exit;
@@ -1888,12 +1897,9 @@ check_next_rec:
 	}
 
 	if (ins_fold != next_fold) {
-
 		if (!locked) {
-
-			btr_search_x_lock(index);
-
-			locked = TRUE;
+			locked = true;
+			rw_lock_x_lock(latch);
 
 			if (!btr_search_enabled) {
 				goto function_exit;
@@ -1912,7 +1918,7 @@ function_exit:
 		mem_heap_free(heap);
 	}
 	if (locked) {
-		btr_search_x_unlock(index);
+		rw_lock_x_unlock(latch);
 	}
 }
 
@@ -2019,7 +2025,7 @@ btr_search_hash_table_validate(ulint hash_table_id)
 				     == BUF_BLOCK_REMOVE_HASH);
 			}
 
-			ut_a(!dict_index_is_ibuf(block->index));
+			ut_ad(!dict_index_is_ibuf(block->index));
 			ut_ad(block->page.id.space() == block->index->space);
 
 			page_index_id = btr_page_get_index_id(block->frame);
diff --git a/storage/innobase/buf/buf0buf.cc b/storage/innobase/buf/buf0buf.cc
index 11c2e0e5ad5..3beae8982b6 100644
--- a/storage/innobase/buf/buf0buf.cc
+++ b/storage/innobase/buf/buf0buf.cc
@@ -3165,66 +3165,6 @@ DECLARE_THREAD(buf_resize_thread)(void*)
 	OS_THREAD_DUMMY_RETURN;
 }
 
-#ifdef BTR_CUR_HASH_ADAPT
-/** Clear the adaptive hash index on all pages in the buffer pool. */
-void
-buf_pool_clear_hash_index()
-{
-	ulint	p;
-
-	ut_ad(btr_search_own_all(RW_LOCK_X));
-	ut_ad(!buf_pool_resizing);
-	ut_ad(!btr_search_enabled);
-
-	for (p = 0; p < srv_buf_pool_instances; p++) {
-		buf_pool_t*	buf_pool = buf_pool_from_array(p);
-		buf_chunk_t*	chunks	= buf_pool->chunks;
-		buf_chunk_t*	chunk	= chunks + buf_pool->n_chunks;
-
-		while (--chunk >= chunks) {
-			buf_block_t*	block	= chunk->blocks;
-			ulint		i	= chunk->size;
-
-			for (; i--; block++) {
-				dict_index_t*	index	= block->index;
-				assert_block_ahi_valid(block);
-
-				/* We can set block->index = NULL
-				and block->n_pointers = 0
-				when btr_search_own_all(RW_LOCK_X);
-				see the comments in buf0buf.h */
-
-				if (!index) {
-# if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
-					ut_a(!block->n_pointers);
-# endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
-					continue;
-				}
-
-				ut_d(buf_page_state state
-				     = buf_block_get_state(block));
-				/* Another thread may have set the
-				state to BUF_BLOCK_REMOVE_HASH in
-				buf_LRU_block_remove_hashed().
-
-				The state change in buf_page_realloc()
-				is not observable here, because in
-				that case we would have !block->index.
-
-				In the end, the entire adaptive hash
-				index will be removed. */
-				ut_ad(state == BUF_BLOCK_FILE_PAGE
-				      || state == BUF_BLOCK_REMOVE_HASH);
-# if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
-				block->n_pointers = 0;
-# endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
-				block->index = NULL;
-			}
-		}
-	}
-}
-#endif /* BTR_CUR_HASH_ADAPT */
-
 /********************************************************************//**
 Relocate a buffer control block.  Relocates the block on the LRU list
 and in buf_pool->page_hash.  Does not relocate bpage->list.
@@ -4207,7 +4147,7 @@ static buf_block_t* buf_page_mtr_lock(buf_block_t *block,
   {
   case RW_NO_LATCH:
     fix_type= MTR_MEMO_BUF_FIX;
-    break;
+    goto done;
   case RW_S_LATCH:
     rw_lock_s_lock_inline(&block->lock, 0, file, line);
     fix_type= MTR_MEMO_PAGE_S_FIX;
@@ -4223,6 +4163,15 @@ static buf_block_t* buf_page_mtr_lock(buf_block_t *block,
     break;
   }
 
+#ifdef BTR_CUR_HASH_ADAPT
+  {
+    dict_index_t *index= block->index;
+    if (index && index->freed())
+      btr_search_drop_page_hash_index(block);
+  }
+#endif /* BTR_CUR_HASH_ADAPT */
+
+done:
   mtr_memo_push(mtr, block, fix_type);
   return block;
 }
@@ -4540,6 +4489,7 @@ evict_from_pool:
 			buf_pool_mutex_exit(buf_pool);
 			return(NULL);
 		}
+
 		break;
 
 	case BUF_BLOCK_ZIP_PAGE:
@@ -5087,9 +5037,11 @@ buf_page_get_known_nowait(
 
 	buf_pool = buf_pool_from_block(block);
 
+#ifdef BTR_CUR_HASH_ADAPT
 	if (mode == BUF_MAKE_YOUNG) {
 		buf_page_make_young_if_needed(&block->page);
 	}
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	ut_ad(!ibuf_inside(mtr) || mode == BUF_KEEP_OLD);
 
@@ -5132,9 +5084,12 @@ buf_page_get_known_nowait(
 		deleting a record from SYS_INDEXES. This check will be
 		skipped in recv_recover_page() as well. */
 
-		buf_page_mutex_enter(block);
-		ut_a(!block->page.file_page_was_freed);
-		buf_page_mutex_exit(block);
+# ifdef BTR_CUR_HASH_ADAPT
+		ut_ad(!block->page.file_page_was_freed
+		      || (block->index && block->index->freed()));
+# else /* BTR_CUR_HASH_ADAPT */
+		ut_ad(!block->page.file_page_was_freed);
+# endif /* BTR_CUR_HASH_ADAPT */
 	}
 #endif /* UNIV_DEBUG */
 
@@ -5627,6 +5582,12 @@ buf_page_create(
 		rw_lock_x_unlock(hash_lock);
 
 		buf_block_free(free_block);
+#ifdef BTR_CUR_HASH_ADAPT
+		if (block->page.state == BUF_BLOCK_FILE_PAGE
+		    && UNIV_LIKELY_NULL(block->index)) {
+			btr_search_drop_page_hash_index(block);
+		}
+#endif /* BTR_CUR_HASH_ADAPT */
 
 		if (!recv_recovery_is_on()) {
 			return buf_page_get_with_no_latch(page_id, page_size,
diff --git a/storage/innobase/buf/buf0lru.cc b/storage/innobase/buf/buf0lru.cc
index 9feebd9a08e..6e2dba77513 100644
--- a/storage/innobase/buf/buf0lru.cc
+++ b/storage/innobase/buf/buf0lru.cc
@@ -222,166 +222,6 @@ buf_LRU_evict_from_unzip_LRU(
 }
 
 #ifdef BTR_CUR_HASH_ADAPT
-/** Attempts to drop page hash index on a batch of pages belonging to a
-particular space id.
-@param[in]	space_id	space id
-@param[in]	arr		array of page_no
-@param[in]	count		number of entries in array */
-static
-void
-buf_LRU_drop_page_hash_batch(ulint space_id, const ulint* arr, ulint count)
-{
-	ut_ad(count <= BUF_LRU_DROP_SEARCH_SIZE);
-
-	for (const ulint* const end = arr + count; arr != end; ) {
-		/* While our only caller
-		buf_LRU_drop_page_hash_for_tablespace()
-		is being executed for DROP TABLE or similar,
-		the table cannot be evicted from the buffer pool. */
-		btr_search_drop_page_hash_when_freed(
-			page_id_t(space_id, *arr++));
-	}
-}
-
-/******************************************************************//**
-When doing a DROP TABLE/DISCARD TABLESPACE we have to drop all page
-hash index entries belonging to that table. This function tries to
-do that in batch. Note that this is a 'best effort' attempt and does
-not guarantee that ALL hash entries will be removed. */
-static
-void
-buf_LRU_drop_page_hash_for_tablespace(
-/*==================================*/
-	buf_pool_t*	buf_pool,	/*!< in: buffer pool instance */
-	ulint		id)		/*!< in: space id */
-{
-	ulint*	page_arr = static_cast<ulint*>(ut_malloc_nokey(
-			sizeof(ulint) * BUF_LRU_DROP_SEARCH_SIZE));
-
-	ulint	num_entries = 0;
-
-	buf_pool_mutex_enter(buf_pool);
-
-scan_again:
-	for (buf_page_t* bpage = UT_LIST_GET_LAST(buf_pool->LRU);
-	     bpage != NULL;
-	     /* No op */) {
-
-		buf_page_t*	prev_bpage = UT_LIST_GET_PREV(LRU, bpage);
-
-		ut_a(buf_page_in_file(bpage));
-
-		if (buf_page_get_state(bpage) != BUF_BLOCK_FILE_PAGE
-		    || bpage->id.space() != id
-		    || bpage->io_fix != BUF_IO_NONE) {
-			/* Compressed pages are never hashed.
-			Skip blocks of other tablespaces.
-			Skip I/O-fixed blocks (to be dealt with later). */
-next_page:
-			bpage = prev_bpage;
-			continue;
-		}
-
-		buf_block_t*	block = reinterpret_cast<buf_block_t*>(bpage);
-
-		mutex_enter(&block->mutex);
-
-		/* This debug check uses a dirty read that could
-		theoretically cause false positives while
-		buf_pool_clear_hash_index() is executing.
-		(Other conflicting access paths to the adaptive hash
-		index should not be possible, because when a
-		tablespace is being discarded or dropped, there must
-		be no concurrect access to the contained tables.) */
-		assert_block_ahi_valid(block);
-
-		bool	skip = bpage->buf_fix_count > 0 || !block->index;
-
-		mutex_exit(&block->mutex);
-
-		if (skip) {
-			/* Skip this block, because there are
-			no adaptive hash index entries
-			pointing to it, or because we cannot
-			drop them due to the buffer-fix. */
-			goto next_page;
-		}
-
-		/* Store the page number so that we can drop the hash
-		index in a batch later. */
-		page_arr[num_entries] = bpage->id.page_no();
-		ut_a(num_entries < BUF_LRU_DROP_SEARCH_SIZE);
-		++num_entries;
-
-		if (num_entries < BUF_LRU_DROP_SEARCH_SIZE) {
-			goto next_page;
-		}
-
-		/* Array full. We release the buf_pool->mutex to obey
-		the latching order. */
-		buf_pool_mutex_exit(buf_pool);
-
-		buf_LRU_drop_page_hash_batch(id, page_arr, num_entries);
-
-		num_entries = 0;
-
-		buf_pool_mutex_enter(buf_pool);
-
-		/* Note that we released the buf_pool mutex above
-		after reading the prev_bpage during processing of a
-		page_hash_batch (i.e.: when the array was full).
-		Because prev_bpage could belong to a compressed-only
-		block, it may have been relocated, and thus the
-		pointer cannot be trusted. Because bpage is of type
-		buf_block_t, it is safe to dereference.
-
-		bpage can change in the LRU list. This is OK because
-		this function is a 'best effort' to drop as many
-		search hash entries as possible and it does not
-		guarantee that ALL such entries will be dropped. */
-
-		/* If, however, bpage has been removed from LRU list
-		to the free list then we should restart the scan.
-		bpage->state is protected by buf_pool mutex. */
-		if (bpage != NULL
-		    && buf_page_get_state(bpage) != BUF_BLOCK_FILE_PAGE) {
-
-			goto scan_again;
-		}
-	}
-
-	buf_pool_mutex_exit(buf_pool);
-
-	/* Drop any remaining batch of search hashed pages. */
-	buf_LRU_drop_page_hash_batch(id, page_arr, num_entries);
-	ut_free(page_arr);
-}
-
-/** Try to drop the adaptive hash index for a tablespace.
-@param[in,out]	table	table
-@return	whether anything was dropped */
-bool buf_LRU_drop_page_hash_for_tablespace(dict_table_t* table)
-{
-	for (dict_index_t* index = dict_table_get_first_index(table);
-	     index != NULL;
-	     index = dict_table_get_next_index(index)) {
-		if (btr_search_info_get_ref_count(btr_search_get_info(index),
-						  index)) {
-			goto drop_ahi;
-		}
-	}
-
-	return false;
-drop_ahi:
-	ulint id = table->space;
-	for (ulint i = 0; i < srv_buf_pool_instances; i++) {
-		buf_LRU_drop_page_hash_for_tablespace(buf_pool_from_array(i),
-						      id);
-	}
-
-	return true;
-}
-
 /******************************************************************//**
 While flushing (or removing dirty) pages from a tablespace we don't
 want to hog the CPU and resources. Release the buffer pool and block
diff --git a/storage/innobase/dict/dict0crea.cc b/storage/innobase/dict/dict0crea.cc
index 54d2eca245f..1a3d6c51d98 100644
--- a/storage/innobase/dict/dict0crea.cc
+++ b/storage/innobase/dict/dict0crea.cc
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2019, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -26,7 +26,9 @@ Created 1/8/1996 Heikki Tuuri
 
 #include "dict0crea.h"
 #include "btr0pcur.h"
-#include "btr0btr.h"
+#ifdef BTR_CUR_HASH_ADAPT
+# include "btr0sea.h"
+#endif /* BTR_CUR_HASH_ADAPT */
 #include "page0page.h"
 #include "mach0data.h"
 #include "dict0boot.h"
@@ -1528,6 +1530,9 @@ dict_create_index_step(
 					&node->table->fts->cache->init_lock);
 			}
 
+#ifdef BTR_CUR_HASH_ADAPT
+			ut_ad(!node->index->search_info->ref_count);
+#endif /* BTR_CUR_HASH_ADAPT */
 			dict_index_remove_from_cache(node->table, node->index);
 			node->index = NULL;
 
diff --git a/storage/innobase/dict/dict0dict.cc b/storage/innobase/dict/dict0dict.cc
index 8f94ccb4c63..cff213dea3d 100644
--- a/storage/innobase/dict/dict0dict.cc
+++ b/storage/innobase/dict/dict0dict.cc
@@ -1361,25 +1361,12 @@ dict_table_can_be_evicted(
 		}
 
 #ifdef BTR_CUR_HASH_ADAPT
+		/* We cannot really evict the table if adaptive hash
+		index entries are pointing to any of its indexes. */
 		for (dict_index_t* index = dict_table_get_first_index(table);
 		     index != NULL;
 		     index = dict_table_get_next_index(index)) {
-
-			btr_search_t*	info = btr_search_get_info(index);
-
-			/* We are not allowed to free the in-memory index
-			struct dict_index_t until all entries in the adaptive
-			hash index that point to any of the page belonging to
-			his b-tree index are dropped. This is so because
-			dropping of these entries require access to
-			dict_index_t struct. To avoid such scenario we keep
-			a count of number of such pages in the search_info and
-			only free the dict_index_t struct when this count
-			drops to zero.
-
-			See also: dict_index_remove_from_cache_low() */
-
-			if (btr_search_info_get_ref_count(info, index) > 0) {
+			if (index->n_ahi_pages()) {
 				return(FALSE);
 			}
 		}
@@ -1391,6 +1378,71 @@ dict_table_can_be_evicted(
 	return(FALSE);
 }
 
+#ifdef BTR_CUR_HASH_ADAPT
+/** @return a clone of this */
+dict_index_t *dict_index_t::clone() const
+{
+  ut_ad(n_fields);
+  ut_ad(!(type & (DICT_IBUF | DICT_SPATIAL | DICT_FTS)));
+  ut_ad(online_status == ONLINE_INDEX_COMPLETE);
+  ut_ad(is_committed());
+  ut_ad(!is_dummy);
+  ut_ad(!parser);
+  ut_ad(!index_fts_syncing);
+  ut_ad(!online_log);
+  ut_ad(!rtr_track);
+
+  const size_t size= sizeof *this + n_fields * sizeof(*fields) +
+#ifdef BTR_CUR_ADAPT
+    sizeof *search_info +
+#endif
+    1 + strlen(name) +
+    n_uniq * (sizeof *stat_n_diff_key_vals +
+              sizeof *stat_n_sample_sizes +
+              sizeof *stat_n_non_null_key_vals);
+
+  mem_heap_t* heap= mem_heap_create(size);
+  dict_index_t *index= static_cast<dict_index_t*>(mem_heap_dup(heap, this,
+                                                               sizeof *this));
+  *index= *this;
+  rw_lock_create(index_tree_rw_lock_key, &index->lock, SYNC_INDEX_TREE);
+  index->heap= heap;
+  index->name= mem_heap_strdup(heap, name);
+  index->fields= static_cast<dict_field_t*>
+    (mem_heap_dup(heap, fields, n_fields * sizeof *fields));
+#ifdef BTR_CUR_ADAPT
+  index->search_info= btr_search_info_create(index->heap);
+#endif /* BTR_CUR_ADAPT */
+  index->stat_n_diff_key_vals= static_cast<ib_uint64_t*>
+    (mem_heap_zalloc(heap, n_uniq * sizeof *stat_n_diff_key_vals));
+  index->stat_n_sample_sizes= static_cast<ib_uint64_t*>
+    (mem_heap_zalloc(heap, n_uniq * sizeof *stat_n_sample_sizes));
+  index->stat_n_non_null_key_vals= static_cast<ib_uint64_t*>
+    (mem_heap_zalloc(heap, n_uniq * sizeof *stat_n_non_null_key_vals));
+  memset(&index->zip_pad, 0, sizeof index->zip_pad);
+  return index;
+}
+
+/** Clone this index for lazy dropping of the adaptive hash.
+@return this or a clone */
+dict_index_t *dict_index_t::clone_if_needed()
+{
+  if (!search_info->ref_count)
+    return this;
+  dict_index_t *prev= UT_LIST_GET_PREV(indexes, this);
+
+  UT_LIST_REMOVE(table->indexes, this);
+  UT_LIST_ADD_LAST(table->freed_indexes, this);
+  dict_index_t *index= clone();
+  set_freed();
+  if (prev)
+    UT_LIST_INSERT_AFTER(table->indexes, prev, index);
+  else
+    UT_LIST_ADD_FIRST(table->indexes, index);
+  return index;
+}
+#endif /* BTR_CUR_HASH_ADAPT */
+
 /**********************************************************************//**
 Make room in the table cache by evicting an unused table. The unused table
 should not be part of FK relationship and currently not used in any user
@@ -2081,6 +2133,14 @@ dict_table_remove_from_cache_low(
 		UT_DELETE(table->vc_templ);
 	}
 
+#ifdef BTR_CUR_HASH_ADAPT
+	if (UNIV_UNLIKELY(UT_LIST_GET_LEN(table->freed_indexes) != 0)) {
+		table->vc_templ = NULL;
+		table->id = 0;
+		return;
+	}
+#endif /* BTR_CUR_HASH_ADAPT */
+
 	dict_mem_table_free(table);
 }
 
@@ -2310,6 +2370,8 @@ dict_index_remove_from_cache_low(
 	ut_ad(table->magic_n == DICT_TABLE_MAGIC_N);
 	ut_ad(index->magic_n == DICT_INDEX_MAGIC_N);
 	ut_ad(mutex_own(&dict_sys->mutex));
+	ut_ad(table->id);
+	ut_ad(!index->freed());
 
 	/* No need to acquire the dict_index_t::lock here because
 	there can't be any active operations on this index (or table). */
@@ -2319,13 +2381,22 @@ dict_index_remove_from_cache_low(
 		row_log_free(index->online_log);
 	}
 
+	/* Remove the index from the list of indexes of the table */
+	UT_LIST_REMOVE(table->indexes, index);
+
+	/* The index is being dropped, remove any compression stats for it. */
+	if (!lru_evict && DICT_TF_GET_ZIP_SSIZE(index->table->flags)) {
+		mutex_enter(&page_zip_stat_per_index_mutex);
+		page_zip_stat_per_index.erase(index->id);
+		mutex_exit(&page_zip_stat_per_index_mutex);
+	}
+
+	/* Remove the index from affected virtual column index list */
+	index->detach_columns();
+
 #ifdef BTR_CUR_HASH_ADAPT
 	/* We always create search info whether or not adaptive
 	hash index is enabled or not. */
-	btr_search_t*	info = btr_search_get_info(index);
-	ulint		retries = 0;
-	ut_ad(info);
-
 	/* We are not allowed to free the in-memory index struct
 	dict_index_t until all entries in the adaptive hash index
 	that point to any of the page belonging to his b-tree index
@@ -2335,31 +2406,15 @@ dict_index_remove_from_cache_low(
 	only free the dict_index_t struct when this count drops to
 	zero. See also: dict_table_can_be_evicted() */
 
-	do {
-		if (!btr_search_info_get_ref_count(info, index)
-		    || !buf_LRU_drop_page_hash_for_tablespace(table)) {
-			break;
-		}
-
-		ut_a(++retries < 10000);
-	} while (srv_shutdown_state == SRV_SHUTDOWN_NONE || !lru_evict);
+	if (index->n_ahi_pages()) {
+		index->set_freed();
+		UT_LIST_ADD_LAST(table->freed_indexes, index);
+		return;
+	}
 #endif /* BTR_CUR_HASH_ADAPT */
 
 	rw_lock_free(&index->lock);
 
-	/* The index is being dropped, remove any compression stats for it. */
-	if (!lru_evict && DICT_TF_GET_ZIP_SSIZE(index->table->flags)) {
-		mutex_enter(&page_zip_stat_per_index_mutex);
-		page_zip_stat_per_index.erase(index->id);
-		mutex_exit(&page_zip_stat_per_index_mutex);
-	}
-
-	/* Remove the index from the list of indexes of the table */
-	UT_LIST_REMOVE(table->indexes, index);
-
-	/* Remove the index from affected virtual column index list */
-	index->detach_columns();
-
 	dict_mem_index_free(index);
 }
 
@@ -5698,7 +5753,7 @@ dict_set_corrupted(
 
 	btr_cur_search_to_nth_level(sys_index, 0, tuple, PAGE_CUR_LE,
 				    BTR_MODIFY_LEAF,
-				    &cursor, 0, __FILE__, __LINE__, &mtr);
+				    &cursor, 0, __FILE__, __LINE__, &mtr, 0);
 
 	if (cursor.low_match == dtuple_get_n_fields(tuple)) {
 		/* UPDATE SYS_INDEXES SET TYPE=index->type
@@ -5800,7 +5855,7 @@ dict_index_set_merge_threshold(
 
 	btr_cur_search_to_nth_level(sys_index, 0, tuple, PAGE_CUR_GE,
 				    BTR_MODIFY_LEAF,
-				    &cursor, 0, __FILE__, __LINE__, &mtr);
+				    &cursor, 0, __FILE__, __LINE__, &mtr, 0);
 
 	if (cursor.up_match == dtuple_get_n_fields(tuple)
 	    && rec_get_n_fields_old(btr_cur_get_rec(&cursor))
diff --git a/storage/innobase/dict/dict0mem.cc b/storage/innobase/dict/dict0mem.cc
index 21a3c743f52..8327318e46c 100644
--- a/storage/innobase/dict/dict0mem.cc
+++ b/storage/innobase/dict/dict0mem.cc
@@ -126,6 +126,9 @@ dict_mem_table_create(
 	lock_table_lock_list_init(&table->locks);
 
 	UT_LIST_INIT(table->indexes, &dict_index_t::indexes);
+#ifdef BTR_CUR_HASH_ADAPT
+	UT_LIST_INIT(table->freed_indexes, &dict_index_t::indexes);
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	table->heap = heap;
 
@@ -181,6 +184,10 @@ dict_mem_table_free(
 {
 	ut_ad(table);
 	ut_ad(table->magic_n == DICT_TABLE_MAGIC_N);
+	ut_ad(UT_LIST_GET_LEN(table->indexes) == 0);
+#ifdef BTR_CUR_HASH_ADAPT
+	ut_ad(UT_LIST_GET_LEN(table->freed_indexes) == 0);
+#endif /* BTR_CUR_HASH_ADAPT */
 	ut_d(table->cached = FALSE);
 
 	if (dict_table_has_fts_index(table)
diff --git a/storage/innobase/dict/dict0stats.cc b/storage/innobase/dict/dict0stats.cc
index dab30a218e6..0da77dfdff7 100644
--- a/storage/innobase/dict/dict0stats.cc
+++ b/storage/innobase/dict/dict0stats.cc
@@ -424,6 +424,9 @@ dict_stats_table_clone_create(
 	dict_table_stats_latch_create(t, false);
 
 	UT_LIST_INIT(t->indexes, &dict_index_t::indexes);
+#ifdef BTR_CUR_HASH_ADAPT
+	UT_LIST_INIT(t->freed_indexes, &dict_index_t::indexes);
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	for (index = dict_table_get_first_index(table);
 	     index != NULL;
@@ -4005,6 +4008,9 @@ test_dict_stats_save()
 	table.stat_clustered_index_size = TEST_CLUSTERED_INDEX_SIZE;
 	table.stat_sum_of_other_index_sizes = TEST_SUM_OF_OTHER_INDEX_SIZES;
 	UT_LIST_INIT(table.indexes, &dict_index_t::indexes);
+#ifdef BTR_CUR_HASH_ADAPT
+	UT_LIST_INIT(table.freed_indexes, &dict_index_t::indexes);
+#endif /* BTR_CUR_HASH_ADAPT */
 	UT_LIST_ADD_LAST(table.indexes, &index1);
 	UT_LIST_ADD_LAST(table.indexes, &index2);
 	ut_d(table.magic_n = DICT_TABLE_MAGIC_N);
@@ -4154,6 +4160,9 @@ test_dict_stats_fetch_from_ps()
 	/* craft a dummy dict_table_t */
 	table.name.m_name = (char*) (TEST_DATABASE_NAME "/" TEST_TABLE_NAME);
 	UT_LIST_INIT(table.indexes, &dict_index_t::indexes);
+#ifdef BTR_CUR_HASH_ADAPT
+	UT_LIST_INIT(table.freed_indexes, &dict_index_t::indexes);
+#endif /* BTR_CUR_HASH_ADAPT */
 	UT_LIST_ADD_LAST(table.indexes, &index1);
 	UT_LIST_ADD_LAST(table.indexes, &index2);
 	ut_d(table.magic_n = DICT_TABLE_MAGIC_N);
diff --git a/storage/innobase/fsp/fsp0fsp.cc b/storage/innobase/fsp/fsp0fsp.cc
index d308ff9de71..974a514e637 100644
--- a/storage/innobase/fsp/fsp0fsp.cc
+++ b/storage/innobase/fsp/fsp0fsp.cc
@@ -2976,8 +2976,6 @@ fseg_mark_page_used(
 @param[in,out]	space		tablespace
 @param[in]	offset		page number
 @param[in]	page_size	page size
-@param[in]	ahi		whether we may need to drop the adaptive
-hash index
 @param[in,out]	mtr		mini-transaction */
 static
 void
@@ -2986,9 +2984,6 @@ fseg_free_page_low(
 	fil_space_t*		space,
 	page_no_t		offset,
 	const page_size_t&	page_size,
-#ifdef BTR_CUR_HASH_ADAPT
-	bool			ahi,
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*			mtr)
 {
 	xdes_t*	descr;
@@ -3003,15 +2998,6 @@ fseg_free_page_low(
 	      == FSEG_MAGIC_N_VALUE);
 	ut_ad(!((page_offset(seg_inode) - FSEG_ARR_OFFSET) % FSEG_INODE_SIZE));
 	ut_d(space->modify_check(*mtr));
-#ifdef BTR_CUR_HASH_ADAPT
-	/* Drop search system page hash index if the page is found in
-	the pool and is hashed */
-
-	if (ahi) {
-		btr_search_drop_page_hash_when_freed(
-			page_id_t(space->id, offset));
-	}
-#endif /* BTR_CUR_HASH_ADAPT */
 
 	descr = xdes_get_descriptor(space, offset, page_size, mtr);
 
@@ -3097,22 +3083,13 @@ fseg_free_page_low(
 	}
 }
 
-#ifndef BTR_CUR_HASH_ADAPT
-# define fseg_free_page_low(inode, space, offset, page_size, ahi, mtr)	\
-	fseg_free_page_low(inode, space, offset, page_size, mtr)
-#endif /* !BTR_CUR_HASH_ADAPT */
-
 /**********************************************************************//**
 Frees a single page of a segment. */
 void
-fseg_free_page_func(
+fseg_free_page(
 	fseg_header_t*	seg_header, /*!< in: segment header */
 	ulint		space_id,/*!< in: space id */
 	ulint		page,	/*!< in: page offset */
-#ifdef BTR_CUR_HASH_ADAPT
-	bool		ahi,	/*!< in: whether we may need to drop
-				the adaptive hash index */
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*		mtr)	/*!< in/out: mini-transaction */
 {
 	DBUG_ENTER("fseg_free_page");
@@ -3128,7 +3105,7 @@ fseg_free_page_func(
 				   &iblock);
 	fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
 
-	fseg_free_page_low(seg_inode, space, page, page_size, ahi, mtr);
+	fseg_free_page_low(seg_inode, space, page, page_size, mtr);
 
 	ut_d(buf_page_set_file_page_was_freed(page_id_t(space_id, page)));
 
@@ -3169,8 +3146,6 @@ fseg_page_is_free(fil_space_t* space, unsigned page)
 @param[in,out]	space		tablespace
 @param[in]	page_size	page size
 @param[in]	page		page number in the extent
-@param[in]	ahi		whether we may need to drop
-				the adaptive hash index
 @param[in,out]	mtr		mini-transaction */
 MY_ATTRIBUTE((nonnull))
 static
@@ -3180,9 +3155,6 @@ fseg_free_extent(
 	fil_space_t*		space,
 	const page_size_t&	page_size,
 	ulint			page,
-#ifdef BTR_CUR_HASH_ADAPT
-	bool			ahi,
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*			mtr)
 {
 	xdes_t*	descr;
@@ -3203,23 +3175,6 @@ fseg_free_extent(
 	const ulint first_page_in_extent = page - (page % FSP_EXTENT_SIZE);
 #endif /* BTR_CUR_HASH_ADAPT || UNIV_DEBUG */
 
-#ifdef BTR_CUR_HASH_ADAPT
-	if (ahi) {
-		for (ulint i = 0; i < FSP_EXTENT_SIZE; i++) {
-			if (!xdes_mtr_get_bit(descr, XDES_FREE_BIT, i, mtr)) {
-
-				/* Drop search system page hash index
-				if the page is found in the pool and
-				is hashed */
-
-				btr_search_drop_page_hash_when_freed(
-					page_id_t(space->id,
-						  first_page_in_extent + i));
-			}
-		}
-	}
-#endif /* BTR_CUR_HASH_ADAPT */
-
 	if (xdes_is_full(descr, mtr)) {
 		flst_remove(seg_inode + FSEG_FULL,
 			    descr + XDES_FLST_NODE, mtr);
@@ -3251,27 +3206,18 @@ fseg_free_extent(
 #endif /* UNIV_DEBUG */
 }
 
-#ifndef BTR_CUR_HASH_ADAPT
-# define fseg_free_extent(inode, space, page_size, page, ahi, mtr)	\
-	fseg_free_extent(inode, space, page_size, page, mtr)
-#endif /* !BTR_CUR_HASH_ADAPT */
-
 /**********************************************************************//**
 Frees part of a segment. This function can be used to free a segment by
 repeatedly calling this function in different mini-transactions. Doing
 the freeing in a single mini-transaction might result in too big a
 mini-transaction.
-@return TRUE if freeing completed */
-ibool
-fseg_free_step_func(
+@return whether the freeing was completed */
+bool
+fseg_free_step(
 	fseg_header_t*	header,	/*!< in, own: segment header; NOTE: if the header
 				resides on the first page of the frag list
 				of the segment, this pointer becomes obsolete
 				after the last freeing step */
-#ifdef BTR_CUR_HASH_ADAPT
-	bool		ahi,	/*!< in: whether we may need to drop
-				the adaptive hash index */
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*		mtr)	/*!< in/out: mini-transaction */
 {
 	ulint		n;
@@ -3303,7 +3249,7 @@ fseg_free_step_func(
 	if (inode == NULL) {
 		ib::info() << "Double free of inode from "
 			<< page_id_t(space_id, header_page);
-		DBUG_RETURN(TRUE);
+		DBUG_RETURN(true);
 	}
 
 	fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
@@ -3313,9 +3259,9 @@ fseg_free_step_func(
 		/* Free the extent held by the segment */
 		page = xdes_get_offset(descr);
 
-		fseg_free_extent(inode, space, page_size, page, ahi, mtr);
+		fseg_free_extent(inode, space, page_size, page, mtr);
 
-		DBUG_RETURN(FALSE);
+		DBUG_RETURN(false);
 	}
 
 	/* Free a frag page */
@@ -3325,13 +3271,13 @@ fseg_free_step_func(
 		/* Freeing completed: free the segment inode */
 		fsp_free_seg_inode(space, page_size, inode, mtr);
 
-		DBUG_RETURN(TRUE);
+		DBUG_RETURN(true);
 	}
 
 	fseg_free_page_low(
 		inode, space,
 		fseg_get_nth_frag_page_no(inode, n, mtr),
-		page_size, ahi, mtr);
+		page_size, mtr);
 
 	n = fseg_find_last_used_frag_page_slot(inode, mtr);
 
@@ -3339,24 +3285,20 @@ fseg_free_step_func(
 		/* Freeing completed: free the segment inode */
 		fsp_free_seg_inode(space, page_size, inode, mtr);
 
-		DBUG_RETURN(TRUE);
+		DBUG_RETURN(true);
 	}
 
-	DBUG_RETURN(FALSE);
+	DBUG_RETURN(false);
 }
 
 /**********************************************************************//**
 Frees part of a segment. Differs from fseg_free_step because this function
 leaves the header page unfreed.
-@return TRUE if freeing completed, except the header page */
-ibool
-fseg_free_step_not_header_func(
+@return whether the freeing was completed, except for the header page */
+bool
+fseg_free_step_not_header(
 	fseg_header_t*	header,	/*!< in: segment header which must reside on
 				the first fragment page of the segment */
-#ifdef BTR_CUR_HASH_ADAPT
-	bool		ahi,	/*!< in: whether we may need to drop
-				the adaptive hash index */
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*		mtr)	/*!< in/out: mini-transaction */
 {
 	ulint		n;
@@ -3382,29 +3324,27 @@ fseg_free_step_not_header_func(
 		/* Free the extent held by the segment */
 		page = xdes_get_offset(descr);
 
-		fseg_free_extent(inode, space, page_size, page, ahi, mtr);
+		fseg_free_extent(inode, space, page_size, page, mtr);
 
-		return(FALSE);
+		return false;
 	}
 
 	/* Free a frag page */
 
 	n = fseg_find_last_used_frag_page_slot(inode, mtr);
 
-	if (n == ULINT_UNDEFINED) {
-		ut_error;
-	}
+	ut_a(n != ULINT_UNDEFINED);
 
 	page_no = fseg_get_nth_frag_page_no(inode, n, mtr);
 
 	if (page_no == page_get_page_no(page_align(header))) {
 
-		return(TRUE);
+		return true;
 	}
 
-	fseg_free_page_low(inode, space, page_no, page_size, ahi, mtr);
+	fseg_free_page_low(inode, space, page_no, page_size, mtr);
 
-	return(FALSE);
+	return false;
 }
 
 /** Returns the first extent descriptor for a segment.
diff --git a/storage/innobase/gis/gis0sea.cc b/storage/innobase/gis/gis0sea.cc
index 3631ff35874..c372a3f1cd4 100644
--- a/storage/innobase/gis/gis0sea.cc
+++ b/storage/innobase/gis/gis0sea.cc
@@ -590,7 +590,7 @@ rtr_pcur_open_low(
 	}
 
 	btr_cur_search_to_nth_level(index, level, tuple, mode, latch_mode,
-				    btr_cursor, 0, file, line, mtr);
+				    btr_cursor, 0, file, line, mtr, 0);
 	cursor->pos_state = BTR_PCUR_IS_POSITIONED;
 
 	cursor->trx_if_known = NULL;
@@ -759,7 +759,7 @@ static void rtr_get_father_node(
 		btr_cur_search_to_nth_level(
 			index, level, tuple, PAGE_CUR_RTREE_LOCATE,
 			BTR_CONT_MODIFY_TREE, btr_cur, 0,
-			__FILE__, __LINE__, mtr);
+			__FILE__, __LINE__, mtr, 0);
 
 	} else {
 		/* btr_validate */
@@ -769,7 +769,7 @@ static void rtr_get_father_node(
 		btr_cur_search_to_nth_level(
 			index, level, tuple, PAGE_CUR_RTREE_LOCATE,
 			BTR_CONT_MODIFY_TREE, btr_cur, 0,
-			__FILE__, __LINE__, mtr);
+			__FILE__, __LINE__, mtr, 0);
 
 		rec = btr_cur_get_rec(btr_cur);
 		n_fields = dtuple_get_n_fields_cmp(tuple);
diff --git a/storage/innobase/handler/handler0alter.cc b/storage/innobase/handler/handler0alter.cc
index edc7478f7de..9b1d99d3730 100644
--- a/storage/innobase/handler/handler0alter.cc
+++ b/storage/innobase/handler/handler0alter.cc
@@ -254,6 +254,7 @@ struct ha_innobase_inplace_ctx : public inplace_alter_handler_ctx
 		for (ulint i = 0; i < num_to_add_index; i++) {
 			if (!add_index[i]->is_committed()) {
 				add_index[i]->detach_columns();
+				add_index[i]->n_fields = 0;
 			}
 		}
 	}
@@ -8689,21 +8690,14 @@ foreign_fail:
 	}
 
 	if (ctx0->num_to_drop_vcol || ctx0->num_to_add_vcol) {
+		/* FIXME: this workaround does not seem to work with
+		partitioned tables */
 		DBUG_ASSERT(ctx0->old_table->get_ref_count() == 1);
 
 		trx_commit_for_mysql(m_prebuilt->trx);
-#ifdef BTR_CUR_HASH_ADAPT
-		if (btr_search_enabled) {
-			btr_search_disable(false);
-			btr_search_enable();
-		}
-#endif /* BTR_CUR_HASH_ADAPT */
-
-		char	tb_name[FN_REFLEN];
-		ut_strcpy(tb_name, m_prebuilt->table->name.m_name);
-
-		tb_name[strlen(m_prebuilt->table->name.m_name)] = 0;
 
+		char	tb_name[NAME_LEN * 2 + 1 + 1];
+		strcpy(tb_name, m_prebuilt->table->name.m_name);
 		dict_table_close(m_prebuilt->table, true, false);
 		dict_table_remove_from_cache(m_prebuilt->table);
 		m_prebuilt->table = dict_table_open_on_name(
diff --git a/storage/innobase/ibuf/ibuf0ibuf.cc b/storage/innobase/ibuf/ibuf0ibuf.cc
index e02958b4ac3..1ee1624ca8b 100644
--- a/storage/innobase/ibuf/ibuf0ibuf.cc
+++ b/storage/innobase/ibuf/ibuf0ibuf.cc
@@ -2109,7 +2109,7 @@ ibuf_remove_free_page(void)
 	page from it. */
 
 	fseg_free_page(header_page + IBUF_HEADER + IBUF_TREE_SEG_HEADER,
-		       IBUF_SPACE_ID, page_no, false, &mtr);
+		       IBUF_SPACE_ID, page_no, &mtr);
 
 	const page_id_t	page_id(IBUF_SPACE_ID, page_no);
 
diff --git a/storage/innobase/include/btr0cur.h b/storage/innobase/include/btr0cur.h
index 19d0fb397be..f70fe687182 100644
--- a/storage/innobase/include/btr0cur.h
+++ b/storage/innobase/include/btr0cur.h
@@ -154,8 +154,7 @@ Note that if mode is PAGE_CUR_LE, which is used in inserts, then
 cursor->up_match and cursor->low_match both will have sensible values.
 If mode is PAGE_CUR_GE, then up_match will a have a sensible value. */
 dberr_t
-btr_cur_search_to_nth_level(
-/*========================*/
+btr_cur_search_to_nth_level_func(
 	dict_index_t*	index,	/*!< in: index */
 	ulint		level,	/*!< in: the tree level of search */
 	const dtuple_t*	tuple,	/*!< in: data tuple; NOTE: n_fields_cmp in
@@ -181,16 +180,24 @@ btr_cur_search_to_nth_level(
 				to protect the record! */
 	btr_cur_t*	cursor, /*!< in/out: tree cursor; the cursor page is
 				s- or x-latched, but see also above! */
+#ifdef BTR_CUR_HASH_ADAPT
 	ulint		has_search_latch,
 				/*!< in: latch mode the caller
 				currently has on search system:
 				RW_S_LATCH, or 0 */
+#endif /* BTR_CUR_HASH_ADAPT */
 	const char*	file,	/*!< in: file name */
 	unsigned	line,	/*!< in: line where called */
 	mtr_t*		mtr,	/*!< in/out: mini-transaction */
-	ib_uint64_t	autoinc = 0);
+	ib_uint64_t	autoinc);
 				/*!< in: PAGE_ROOT_AUTO_INC to be written
 				(0 if none) */
+#ifdef BTR_CUR_HASH_ADAPT
+# define btr_cur_search_to_nth_level btr_cur_search_to_nth_level_func
+#else /* BTR_CUR_HASH_ADAPT */
+# define btr_cur_search_to_nth_level(ix,lv,t,md,l,cur,has,file,line,m,ai) \
+	btr_cur_search_to_nth_level_func(ix,lv,t,md,l,cur,file,line,m,ai)
+#endif /* BTR_CUR_HASH_ADAPT */
 
 /*****************************************************************//**
 Opens a cursor at either end of an index.
diff --git a/storage/innobase/include/btr0pcur.h b/storage/innobase/include/btr0pcur.h
index b79260e5ab6..26c7ebcee6d 100644
--- a/storage/innobase/include/btr0pcur.h
+++ b/storage/innobase/include/btr0pcur.h
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2019, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -136,15 +136,22 @@ btr_pcur_open_with_no_init_func(
 				page, but assume that the caller uses his
 				btr search latch to protect the record! */
 	btr_pcur_t*	cursor, /*!< in: memory buffer for persistent cursor */
+#ifdef BTR_CUR_HASH_ADAPT
 	ulint		has_search_latch,
 				/*!< in: latch mode the caller
 				currently has on search system:
 				RW_S_LATCH, or 0 */
+#endif /* BTR_CUR_HASH_ADAPT */
 	const char*	file,	/*!< in: file name */
 	unsigned	line,	/*!< in: line where called */
 	mtr_t*		mtr);	/*!< in: mtr */
-#define btr_pcur_open_with_no_init(ix,t,md,l,cur,has,m)			\
+#ifdef BTR_CUR_HASH_ADAPT
+# define btr_pcur_open_with_no_init(ix,t,md,l,cur,has,m)		\
 	btr_pcur_open_with_no_init_func(ix,t,md,l,cur,has,__FILE__,__LINE__,m)
+#else /* BTR_CUR_HASH_ADAPT */
+# define btr_pcur_open_with_no_init(ix,t,md,l,cur,has,m)		\
+	btr_pcur_open_with_no_init_func(ix,t,md,l,cur,__FILE__,__LINE__,m)
+#endif /* BTR_CUR_HASH_ADAPT */
 
 /*****************************************************************//**
 Opens a persistent cursor at either end of an index. */
diff --git a/storage/innobase/include/btr0pcur.ic b/storage/innobase/include/btr0pcur.ic
index 8b0da666250..b5b57050832 100644
--- a/storage/innobase/include/btr0pcur.ic
+++ b/storage/innobase/include/btr0pcur.ic
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2015, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2015, 2019, MariaDB Corporation.
+Copyright (c) 2015, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -496,10 +496,12 @@ btr_pcur_open_with_no_init_func(
 				page, but assume that the caller uses his
 				btr search latch to protect the record! */
 	btr_pcur_t*	cursor, /*!< in: memory buffer for persistent cursor */
+#ifdef BTR_CUR_HASH_ADAPT
 	ulint		has_search_latch,
 				/*!< in: latch mode the caller
 				currently has on search system:
 				RW_S_LATCH, or 0 */
+#endif /* BTR_CUR_HASH_ADAPT */
 	const char*	file,	/*!< in: file name */
 	unsigned	line,	/*!< in: line where called */
 	mtr_t*		mtr)	/*!< in: mtr */
@@ -516,7 +518,7 @@ btr_pcur_open_with_no_init_func(
 
 	err = btr_cur_search_to_nth_level(
 		index, 0, tuple, mode, latch_mode, btr_cursor,
-		has_search_latch, file, line, mtr);
+		has_search_latch, file, line, mtr, 0);
 
 	cursor->pos_state = BTR_PCUR_IS_POSITIONED;
 
diff --git a/storage/innobase/include/btr0sea.h b/storage/innobase/include/btr0sea.h
index 645b3689ff6..b808ba036db 100644
--- a/storage/innobase/include/btr0sea.h
+++ b/storage/innobase/include/btr0sea.h
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2018, MariaDB Corporation.
+Copyright (c) 2018, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -54,15 +54,6 @@ btr_search_disable(
 void
 btr_search_enable();
 
-/** Returns the value of ref_count. The value is protected by latch.
-@param[in]	info		search info
-@param[in]	index		index identifier
-@return ref_count value. */
-ulint
-btr_search_info_get_ref_count(
-	btr_search_t*	info,
-	dict_index_t*	index);
-
 /*********************************************************************//**
 Updates the search info. */
 UNIV_INLINE
@@ -156,18 +147,6 @@ btr_search_update_hash_on_delete(btr_cur_t* cursor);
 bool
 btr_search_validate();
 
-/** X-Lock the search latch (corresponding to given index)
-@param[in]	index	index handler */
-UNIV_INLINE
-void
-btr_search_x_lock(const dict_index_t* index);
-
-/** X-Unlock the search latch (corresponding to given index)
-@param[in]	index	index handler */
-UNIV_INLINE
-void
-btr_search_x_unlock(const dict_index_t* index);
-
 /** Lock all search latches in exclusive mode. */
 UNIV_INLINE
 void
@@ -178,18 +157,6 @@ UNIV_INLINE
 void
 btr_search_x_unlock_all();
 
-/** S-Lock the search latch (corresponding to given index)
-@param[in]	index	index handler */
-UNIV_INLINE
-void
-btr_search_s_lock(const dict_index_t* index);
-
-/** S-Unlock the search latch (corresponding to given index)
-@param[in]	index	index handler */
-UNIV_INLINE
-void
-btr_search_s_unlock(const dict_index_t* index);
-
 /** Lock all search latches in shared mode. */
 UNIV_INLINE
 void
@@ -236,12 +203,8 @@ btr_get_search_table(const dict_index_t* index);
 #else /* BTR_CUR_HASH_ADAPT */
 # define btr_search_sys_create(size)
 # define btr_search_drop_page_hash_index(block)
-# define btr_search_s_lock(index)
-# define btr_search_s_unlock(index)
 # define btr_search_s_lock_all(index)
 # define btr_search_s_unlock_all(index)
-# define btr_search_x_lock(index)
-# define btr_search_x_unlock(index)
 # define btr_search_info_update(index, cursor)
 # define btr_search_move_or_delete_hash_entries(new_block, block, index)
 # define btr_search_update_hash_on_insert(cursor)
@@ -327,6 +290,18 @@ struct btr_search_t{
 };
 
 #ifdef BTR_CUR_HASH_ADAPT
+/** @return number of leaf pages pointed to by the adaptive hash index */
+inline ulint dict_index_t::n_ahi_pages() const
+{
+  if (!btr_search_enabled)
+    return 0;
+  rw_lock_t *latch = btr_get_search_latch(this);
+  rw_lock_s_lock(latch);
+  ulint ref_count= search_info->ref_count;
+  rw_lock_s_unlock(latch);
+  return ref_count;
+}
+
 /** The hash index system */
 struct btr_search_sys_t{
 	hash_table_t**	hash_tables;	/*!< the adaptive hash tables,
diff --git a/storage/innobase/include/btr0sea.ic b/storage/innobase/include/btr0sea.ic
index 4972de16064..90877d23192 100644
--- a/storage/innobase/include/btr0sea.ic
+++ b/storage/innobase/include/btr0sea.ic
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2015, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -62,8 +63,8 @@ btr_search_info_update(
 	dict_index_t*	index,	/*!< in: index of the cursor */
 	btr_cur_t*	cursor)	/*!< in: cursor which was just positioned */
 {
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_S));
-	ut_ad(!rw_lock_own(btr_get_search_latch(index), RW_LOCK_X));
+	ut_ad(!rw_lock_own_flagged(btr_get_search_latch(index),
+				   RW_LOCK_FLAG_X | RW_LOCK_FLAG_S));
 
 	if (dict_index_is_spatial(index) || !btr_search_enabled) {
 		return;
@@ -87,24 +88,6 @@ btr_search_info_update(
 	btr_search_info_update_slow(info, cursor);
 }
 
-/** X-Lock the search latch (corresponding to given index)
-@param[in]	index	index handler */
-UNIV_INLINE
-void
-btr_search_x_lock(const dict_index_t* index)
-{
-	rw_lock_x_lock(btr_get_search_latch(index));
-}
-
-/** X-Unlock the search latch (corresponding to given index)
-@param[in]	index	index handler */
-UNIV_INLINE
-void
-btr_search_x_unlock(const dict_index_t* index)
-{
-	rw_lock_x_unlock(btr_get_search_latch(index));
-}
-
 /** Lock all search latches in exclusive mode. */
 UNIV_INLINE
 void
@@ -125,24 +108,6 @@ btr_search_x_unlock_all()
 	}
 }
 
-/** S-Lock the search latch (corresponding to given index)
-@param[in]	index	index handler */
-UNIV_INLINE
-void
-btr_search_s_lock(const dict_index_t* index)
-{
-	rw_lock_s_lock(btr_get_search_latch(index));
-}
-
-/** S-Unlock the search latch (corresponding to given index)
-@param[in]	index	index handler */
-UNIV_INLINE
-void
-btr_search_s_unlock(const dict_index_t* index)
-{
-	rw_lock_s_unlock(btr_get_search_latch(index));
-}
-
 /** Lock all search latches in shared mode. */
 UNIV_INLINE
 void
diff --git a/storage/innobase/include/buf0buf.h b/storage/innobase/include/buf0buf.h
index 0536e2f8ac6..a9b8ef94bab 100644
--- a/storage/innobase/include/buf0buf.h
+++ b/storage/innobase/include/buf0buf.h
@@ -71,11 +71,13 @@ struct fil_addr_t;
 /* @} */
 /** @name Modes for buf_page_get_known_nowait */
 /* @{ */
-#define BUF_MAKE_YOUNG	51		/*!< Move the block to the
+#ifdef BTR_CUR_HASH_ADAPT
+# define BUF_MAKE_YOUNG	51		/*!< Move the block to the
 					start of the LRU list if there
 					is a danger that the block
 					would drift out of the buffer
 					pool*/
+#endif /* BTR_CUR_HASH_ADAPT */
 #define BUF_KEEP_OLD	52		/*!< Preserve the current LRU
 					position of the block. */
 /* @} */
@@ -282,12 +284,6 @@ extern "C"
 os_thread_ret_t
 DECLARE_THREAD(buf_resize_thread)(void*);
 
-#ifdef BTR_CUR_HASH_ADAPT
-/** Clear the adaptive hash index on all pages in the buffer pool. */
-void
-buf_pool_clear_hash_index();
-#endif /* BTR_CUR_HASH_ADAPT */
-
 /*********************************************************************//**
 Gets the current size of buffer buf_pool in bytes.
 @return size in bytes */
diff --git a/storage/innobase/include/buf0lru.h b/storage/innobase/include/buf0lru.h
index 1efbb1f03ef..a72d98395af 100644
--- a/storage/innobase/include/buf0lru.h
+++ b/storage/innobase/include/buf0lru.h
@@ -49,17 +49,6 @@ These are low-level functions
 /** Minimum LRU list length for which the LRU_old pointer is defined */
 #define BUF_LRU_OLD_MIN_LEN	512	/* 8 megabytes of 16k pages */
 
-#ifdef BTR_CUR_HASH_ADAPT
-struct dict_table_t;
-/** Try to drop the adaptive hash index for a tablespace.
-@param[in,out]	table	table
-@return	whether anything was dropped */
-bool buf_LRU_drop_page_hash_for_tablespace(dict_table_t* table)
-	MY_ATTRIBUTE((warn_unused_result,nonnull));
-#else
-# define buf_LRU_drop_page_hash_for_tablespace(table)
-#endif /* BTR_CUR_HASH_ADAPT */
-
 /** Empty the flush list for all pages belonging to a tablespace.
 @param[in]	id		tablespace identifier
 @param[in,out]	observer	flush observer,
diff --git a/storage/innobase/include/dict0mem.h b/storage/innobase/include/dict0mem.h
index b259d2fb2ad..80d18dcbb2a 100644
--- a/storage/innobase/include/dict0mem.h
+++ b/storage/innobase/include/dict0mem.h
@@ -831,6 +831,9 @@ struct dict_index_t{
 	dict_table_t*	table;	/*!< back pointer to table */
 	unsigned	space:32;
 				/*!< space where the index tree is placed */
+	/** root page number, or FIL_NULL if the index has been detached
+	from storage (DISCARD TABLESPACE or similar),
+	or 1 if the index is in table->freed_indexes */
 	unsigned	page:32;/*!< index tree root page number */
 	unsigned	merge_threshold:6;
 				/*!< In the pessimistic delete, if the page
@@ -1021,11 +1024,23 @@ struct dict_index_t{
 			for (unsigned i = 0; i < n_fields; i++) {
 				fields[i].col->detach(*this);
 			}
-
-			n_fields = 0;
 		}
 	}
 
+#ifdef BTR_CUR_HASH_ADAPT
+  /** @return a clone of this */
+  dict_index_t* clone() const;
+  /** Clone this index for lazy dropping of the adaptive hash index.
+  @return this or a clone */
+  dict_index_t* clone_if_needed();
+  /** @return number of leaf pages pointed to by the adaptive hash index */
+  inline ulint n_ahi_pages() const;
+  /** @return whether mark_freed() had been invoked */
+  bool freed() const { return UNIV_UNLIKELY(page == 1); }
+  /** Note that the index is waiting for btr_search_lazy_free() */
+  void set_freed() { ut_ad(!freed()); page= 1; }
+#endif /* BTR_CUR_HASH_ADAPT */
+
 	/** This ad-hoc class is used by record_size_info only.	*/
 	class record_size_info_t {
 	public:
@@ -1605,6 +1620,11 @@ struct dict_table_t {
 
 	/** List of indexes of the table. */
 	UT_LIST_BASE_NODE_T(dict_index_t)	indexes;
+#ifdef BTR_CUR_HASH_ADAPT
+	/** List of detached indexes that are waiting to be freed along with
+	the last adaptive hash index entry */
+	UT_LIST_BASE_NODE_T(dict_index_t)	freed_indexes;
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	/** List of foreign key constraints in the table. These refer to
 	columns in other tables. */
diff --git a/storage/innobase/include/fsp0fsp.h b/storage/innobase/include/fsp0fsp.h
index a4e3b84b55e..8debdb00013 100644
--- a/storage/innobase/include/fsp0fsp.h
+++ b/storage/innobase/include/fsp0fsp.h
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2013, 2019, MariaDB Corporation.
+Copyright (c) 2013, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -568,22 +568,11 @@ fsp_get_available_space_in_free_extents(
 /**********************************************************************//**
 Frees a single page of a segment. */
 void
-fseg_free_page_func(
+fseg_free_page(
 	fseg_header_t*	seg_header, /*!< in: segment header */
 	ulint		space_id, /*!< in: space id */
 	ulint		page,	/*!< in: page offset */
-#ifdef BTR_CUR_HASH_ADAPT
-	bool		ahi,	/*!< in: whether we may need to drop
-				the adaptive hash index */
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*		mtr);	/*!< in/out: mini-transaction */
-#ifdef BTR_CUR_HASH_ADAPT
-# define fseg_free_page(header, space_id, page, ahi, mtr)	\
-	fseg_free_page_func(header, space_id, page, ahi, mtr)
-#else /* BTR_CUR_HASH_ADAPT */
-# define fseg_free_page(header, space_id, page, ahi, mtr)	\
-	fseg_free_page_func(header, space_id, page, mtr)
-#endif /* BTR_CUR_HASH_ADAPT */
 /** Determine whether a page is free.
 @param[in,out]	space	tablespace
 @param[in]	page	page number
@@ -596,45 +585,25 @@ Frees part of a segment. This function can be used to free a segment
 by repeatedly calling this function in different mini-transactions.
 Doing the freeing in a single mini-transaction might result in
 too big a mini-transaction.
-@return TRUE if freeing completed */
-ibool
-fseg_free_step_func(
+@return whether the freeing was completed */
+bool
+fseg_free_step(
 	fseg_header_t*	header,	/*!< in, own: segment header; NOTE: if the header
 				resides on the first page of the frag list
 				of the segment, this pointer becomes obsolete
 				after the last freeing step */
-#ifdef BTR_CUR_HASH_ADAPT
-	bool		ahi,	/*!< in: whether we may need to drop
-				the adaptive hash index */
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*		mtr)	/*!< in/out: mini-transaction */
 	MY_ATTRIBUTE((warn_unused_result));
-#ifdef BTR_CUR_HASH_ADAPT
-# define fseg_free_step(header, ahi, mtr) fseg_free_step_func(header, ahi, mtr)
-#else /* BTR_CUR_HASH_ADAPT */
-# define fseg_free_step(header, ahi, mtr) fseg_free_step_func(header, mtr)
-#endif /* BTR_CUR_HASH_ADAPT */
 /**********************************************************************//**
 Frees part of a segment. Differs from fseg_free_step because this function
 leaves the header page unfreed.
-@return TRUE if freeing completed, except the header page */
-ibool
-fseg_free_step_not_header_func(
+@return whether the freeing was completed, except for the header page */
+bool
+fseg_free_step_not_header(
 	fseg_header_t*	header,	/*!< in: segment header which must reside on
 				the first fragment page of the segment */
-#ifdef BTR_CUR_HASH_ADAPT
-	bool		ahi,	/*!< in: whether we may need to drop
-				the adaptive hash index */
-#endif /* BTR_CUR_HASH_ADAPT */
 	mtr_t*		mtr)	/*!< in/out: mini-transaction */
 	MY_ATTRIBUTE((warn_unused_result));
-#ifdef BTR_CUR_HASH_ADAPT
-# define fseg_free_step_not_header(header, ahi, mtr)	\
-	fseg_free_step_not_header_func(header, ahi, mtr)
-#else /* BTR_CUR_HASH_ADAPT */
-# define fseg_free_step_not_header(header, ahi, mtr)	\
-	fseg_free_step_not_header_func(header, mtr)
-#endif /* BTR_CUR_HASH_ADAPT */
 
 /** Reset the page type.
 Data files created before MySQL 5.1.48 may contain garbage in FIL_PAGE_TYPE.
diff --git a/storage/innobase/row/row0import.cc b/storage/innobase/row/row0import.cc
index b0fcecf0e39..d92bcb761e4 100644
--- a/storage/innobase/row/row0import.cc
+++ b/storage/innobase/row/row0import.cc
@@ -26,6 +26,9 @@ Created 2012-02-08 by Sunny Bains.
 
 #include "row0import.h"
 #include "btr0pcur.h"
+#ifdef BTR_CUR_HASH_ADAPT
+# include "btr0sea.h"
+#endif
 #include "que0que.h"
 #include "dict0boot.h"
 #include "dict0load.h"
@@ -4017,15 +4020,12 @@ row_import_for_mysql(
 	index entries that point to cached garbage pages in the buffer
 	pool, because PageConverter::operator() only evicted those
 	pages that were replaced by the imported pages. We must
-	discard all remaining adaptive hash index entries, because the
+	detach any remaining adaptive hash index entries, because the
 	adaptive hash index must be a subset of the table contents;
 	false positives are not tolerated. */
-	while (buf_LRU_drop_page_hash_for_tablespace(table)) {
-		if (trx_is_interrupted(trx)
-		    || srv_shutdown_state != SRV_SHUTDOWN_NONE) {
-			err = DB_INTERRUPTED;
-			break;
-		}
+	for (dict_index_t* index = UT_LIST_GET_FIRST(table->indexes); index;
+	     index = UT_LIST_GET_NEXT(indexes, index)) {
+		index = index->clone_if_needed();
 	}
 #endif /* BTR_CUR_HASH_ADAPT */
 
diff --git a/storage/innobase/row/row0ins.cc b/storage/innobase/row/row0ins.cc
index 4c11c241cd6..123566132f4 100644
--- a/storage/innobase/row/row0ins.cc
+++ b/storage/innobase/row/row0ins.cc
@@ -2907,7 +2907,7 @@ row_ins_sec_index_entry_low(
 		err = btr_cur_search_to_nth_level(
 			index, 0, entry, PAGE_CUR_RTREE_INSERT,
 			search_mode,
-			&cursor, 0, __FILE__, __LINE__, &mtr);
+			&cursor, 0, __FILE__, __LINE__, &mtr, 0);
 
 		if (mode == BTR_MODIFY_LEAF && rtr_info.mbr_adj) {
 			mtr_commit(&mtr);
@@ -2922,7 +2922,7 @@ row_ins_sec_index_entry_low(
 			err = btr_cur_search_to_nth_level(
 				index, 0, entry, PAGE_CUR_RTREE_INSERT,
 				search_mode,
-				&cursor, 0, __FILE__, __LINE__, &mtr);
+				&cursor, 0, __FILE__, __LINE__, &mtr, 0);
 			mode = BTR_MODIFY_TREE;
 		}
 
@@ -2934,7 +2934,7 @@ row_ins_sec_index_entry_low(
 		err = btr_cur_search_to_nth_level(
 			index, 0, entry, PAGE_CUR_LE,
 			search_mode,
-			&cursor, 0, __FILE__, __LINE__, &mtr);
+			&cursor, 0, __FILE__, __LINE__, &mtr, 0);
 	}
 
 	if (err != DB_SUCCESS) {
@@ -3028,7 +3028,7 @@ row_ins_sec_index_entry_low(
 			index, 0, entry, PAGE_CUR_LE,
 			(search_mode
 			 & ~(BTR_INSERT | BTR_IGNORE_SEC_UNIQUE)),
-			&cursor, 0, __FILE__, __LINE__, &mtr);
+			&cursor, 0, __FILE__, __LINE__, &mtr, 0);
 	}
 
 	if (row_ins_must_modify_rec(&cursor)) {
diff --git a/storage/innobase/row/row0log.cc b/storage/innobase/row/row0log.cc
index e7b06e5a5b2..e46ee2c4f18 100644
--- a/storage/innobase/row/row0log.cc
+++ b/storage/innobase/row/row0log.cc
@@ -3102,7 +3102,7 @@ row_log_apply_op_low(
 				    ? BTR_MODIFY_TREE
 				    : BTR_MODIFY_LEAF,
 				    &cursor, 0, __FILE__, __LINE__,
-				    &mtr);
+				    &mtr, 0);
 
 	ut_ad(dict_index_get_n_unique(index) > 0);
 	/* This test is somewhat similar to row_ins_must_modify_rec(),
@@ -3151,7 +3151,7 @@ row_log_apply_op_low(
 				btr_cur_search_to_nth_level(
 					index, 0, entry, PAGE_CUR_LE,
 					BTR_MODIFY_TREE, &cursor, 0,
-					__FILE__, __LINE__, &mtr);
+					__FILE__, __LINE__, &mtr, 0);
 
 				/* No other thread than the current one
 				is allowed to modify the index tree.
@@ -3254,7 +3254,7 @@ insert_the_rec:
 				btr_cur_search_to_nth_level(
 					index, 0, entry, PAGE_CUR_LE,
 					BTR_MODIFY_TREE, &cursor, 0,
-					__FILE__, __LINE__, &mtr);
+					__FILE__, __LINE__, &mtr, 0);
 			}
 
 			/* We already determined that the
diff --git a/storage/innobase/row/row0merge.cc b/storage/innobase/row/row0merge.cc
index 1677a47fa45..8c8f1674374 100644
--- a/storage/innobase/row/row0merge.cc
+++ b/storage/innobase/row/row0merge.cc
@@ -46,6 +46,9 @@ Completed by Sunny Bains and Marko Makela
 #include "row0vers.h"
 #include "handler0alter.h"
 #include "btr0bulk.h"
+#ifdef BTR_CUR_ADAPT
+# include "btr0sea.h"
+#endif /* BTR_CUR_ADAPT */
 #include "ut0stage.h"
 #include "fil0crypt.h"
 
@@ -162,7 +165,7 @@ public:
 						    PAGE_CUR_RTREE_INSERT,
 						    BTR_MODIFY_LEAF, &ins_cur,
 						    0, __FILE__, __LINE__,
-						    &mtr);
+						    &mtr, 0);
 
 			/* It need to update MBR in parent entry,
 			so change search mode to BTR_MODIFY_TREE */
@@ -178,7 +181,7 @@ public:
 					m_index, 0, dtuple,
 					PAGE_CUR_RTREE_INSERT,
 					BTR_MODIFY_TREE, &ins_cur, 0,
-					__FILE__, __LINE__, &mtr);
+					__FILE__, __LINE__, &mtr, 0);
 			}
 
 			error = btr_cur_optimistic_insert(
@@ -201,8 +204,7 @@ public:
 					PAGE_CUR_RTREE_INSERT,
 					BTR_MODIFY_TREE,
 					&ins_cur, 0,
-					__FILE__, __LINE__, &mtr);
-
+					__FILE__, __LINE__, &mtr, 0);
 
 				error = btr_cur_pessimistic_insert(
 						flag, &ins_cur, &ins_offsets,
@@ -3770,6 +3772,9 @@ row_merge_drop_indexes(
 					we should exclude FTS entries from
 					prebuilt->ins_node->entry_list
 					in ins_node_create_entry_list(). */
+#ifdef BTR_CUR_HASH_ADAPT
+					ut_ad(!index->search_info->ref_count);
+#endif /* BTR_CUR_HASH_ADAPT */
 					dict_index_remove_from_cache(
 						table, index);
 					index = prev;
diff --git a/storage/innobase/row/row0mysql.cc b/storage/innobase/row/row0mysql.cc
index 45586a1e977..9bbd531cb9a 100644
--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -2459,6 +2459,9 @@ row_create_index_for_mysql(
 		index->table = table;
 
 		err = dict_create_index_tree_in_mem(index, trx);
+#ifdef BTR_CUR_HASH_ADAPT
+		ut_ad(!index->search_info->ref_count);
+#endif /* BTR_CUR_HASH_ADAPT */
 
 		if (err != DB_SUCCESS) {
 			dict_index_remove_from_cache(table, index);
@@ -3372,35 +3375,6 @@ row_drop_table_for_mysql(
 
 	if (!dict_table_is_temporary(table)) {
 		if (table->space != TRX_SYS_SPACE) {
-#ifdef BTR_CUR_HASH_ADAPT
-			/* On DISCARD TABLESPACE, we would not drop the
-			adaptive hash index entries. If the tablespace is
-			missing here, delete-marking the record in SYS_INDEXES
-			would not free any pages in the buffer pool. Thus,
-			dict_index_remove_from_cache() would hang due to
-			adaptive hash index entries existing in the buffer
-			pool.  To prevent this hang, and also to guarantee
-			that btr_search_drop_page_hash_when_freed() will avoid
-			calling btr_search_drop_page_hash_index() while we
-			hold the InnoDB dictionary lock, we will drop any
-			adaptive hash index entries upfront. */
-			const bool immune = is_temp_name
-				|| create_failed
-				|| sqlcom == SQLCOM_CREATE_TABLE
-				|| strstr(table->name.m_name, "/FTS");
-
-			while (buf_LRU_drop_page_hash_for_tablespace(table)) {
-				if ((!immune && trx_is_interrupted(trx))
-				    || srv_shutdown_state
-				    != SRV_SHUTDOWN_NONE) {
-					err = DB_INTERRUPTED;
-					table->to_be_dropped = false;
-					dict_table_close(table, true, false);
-					goto funct_exit;
-				}
-			}
-#endif /* BTR_CUR_HASH_ADAPT */
-
 			/* Delete the link file if used. */
 			if (DICT_TF_HAS_DATA_DIR(table->flags)) {
 				RemoteDatafile::delete_link_file(name);
diff --git a/storage/innobase/row/row0sel.cc b/storage/innobase/row/row0sel.cc
index 6420bf8a707..15486500b37 100644
--- a/storage/innobase/row/row0sel.cc
+++ b/storage/innobase/row/row0sel.cc
@@ -2,7 +2,7 @@
 
 Copyright (c) 1997, 2017, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2008, Google Inc.
-Copyright (c) 2015, 2019, MariaDB Corporation.
+Copyright (c) 2015, 2020, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -1289,23 +1289,17 @@ void
 row_sel_open_pcur(
 /*==============*/
 	plan_t*		plan,		/*!< in: table plan */
-	ibool		search_latch_locked,
-					/*!< in: TRUE if the thread currently
-					has the search latch locked in
-					s-mode */
+#ifdef BTR_CUR_HASH_ADAPT
+	ulint		has_search_latch,
+#endif
 	mtr_t*		mtr)		/*!< in: mtr */
 {
 	dict_index_t*	index;
 	func_node_t*	cond;
 	que_node_t*	exp;
 	ulint		n_fields;
-	ulint		has_search_latch = 0;	/* RW_S_LATCH or 0 */
 	ulint		i;
 
-	if (search_latch_locked) {
-		has_search_latch = RW_S_LATCH;
-	}
-
 	index = plan->index;
 
 	/* Calculate the value of the search tuple: the exact match columns
@@ -1357,6 +1351,11 @@ row_sel_open_pcur(
 	plan->pcur_is_open = TRUE;
 }
 
+#ifndef BTR_CUR_HASH_ADAPT
+# define row_sel_open_pcur(plan, has_search_latch, mtr)	\
+	row_sel_open_pcur(plan, mtr)
+#endif /* !BTR_CUR_HASH_ADAPT */
+
 /*********************************************************************//**
 Restores a stored pcur position to a table index.
 @return TRUE if the cursor should be moved to the next record after we
@@ -1618,12 +1617,6 @@ row_sel(
 
 	ut_ad(thr->run_node == node);
 
-#ifdef BTR_CUR_HASH_ADAPT
-	ibool		search_latch_locked = FALSE;
-#else /* BTR_CUR_HASH_ADAPT */
-# define search_latch_locked false
-#endif /* BTR_CUR_HASH_ADAPT */
-
 	if (node->read_view) {
 		/* In consistent reads, we try to do with the hash index and
 		not to use the buffer page get. This is to reduce memory bus
@@ -1648,6 +1641,10 @@ table_loop:
 
 	plan = sel_node_get_nth_plan(node, node->fetch_table);
 	index = plan->index;
+#ifdef BTR_CUR_HASH_ADAPT
+	ulint has_search_latch = 0;
+	rw_lock_t* const latch = btr_get_search_latch(index);
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	if (plan->n_rows_prefetched > 0) {
 		sel_dequeue_prefetched_row(plan);
@@ -1672,26 +1669,22 @@ table_loop:
 #ifdef BTR_CUR_HASH_ADAPT
 	if (consistent_read && plan->unique_search && !plan->pcur_is_open
 	    && !plan->must_get_clust) {
-		if (!search_latch_locked) {
-			btr_search_s_lock(index);
-
-			search_latch_locked = TRUE;
-		} else if (rw_lock_get_writer(btr_get_search_latch(index))
-				== RW_LOCK_X_WAIT) {
-
+		if (!has_search_latch) {
+			has_search_latch = RW_S_LATCH;
+			rw_lock_s_lock(latch);
+		} else if (rw_lock_get_writer(latch) == RW_LOCK_X_WAIT) {
 			/* There is an x-latch request waiting: release the
 			s-latch for a moment; as an s-latch here is often
 			kept for some 10 searches before being released,
 			a waiting x-latch request would block other threads
 			from acquiring an s-latch for a long time, lowering
 			performance significantly in multiprocessors. */
-
-			btr_search_s_unlock(index);
-			btr_search_s_lock(index);
+			rw_lock_s_unlock(latch);
+			rw_lock_s_lock(latch);
 		}
 
 		switch (row_sel_try_search_shortcut(node, plan,
-						    search_latch_locked,
+						    has_search_latch,
 						    &mtr)) {
 		case SEL_FOUND:
 			goto next_table;
@@ -1709,10 +1702,9 @@ table_loop:
 		mtr.start();
 	}
 
-	if (search_latch_locked) {
-		btr_search_s_unlock(index);
-
-		search_latch_locked = FALSE;
+	if (has_search_latch) {
+		has_search_latch = 0;
+		rw_lock_s_unlock(latch);
 	}
 #endif /* BTR_CUR_HASH_ADAPT */
 
@@ -1720,7 +1712,7 @@ table_loop:
 		/* Evaluate the expressions to build the search tuple and
 		open the cursor */
 
-		row_sel_open_pcur(plan, search_latch_locked, &mtr);
+		row_sel_open_pcur(plan, has_search_latch, &mtr);
 
 		cursor_just_opened = TRUE;
 
@@ -2117,7 +2109,9 @@ skip_lock:
 	}
 
 next_rec:
-	ut_ad(!search_latch_locked);
+#ifdef BTR_CUR_HASH_ADAPT
+	ut_ad(!has_search_latch);
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	if (mtr_has_extra_clust_latch) {
 
@@ -2156,8 +2150,9 @@ next_table:
 
 		plan->cursor_at_end = TRUE;
 	} else {
-		ut_ad(!search_latch_locked);
-
+#ifdef BTR_CUR_HASH_ADAPT
+		ut_ad(!has_search_latch);
+#endif /* BTR_CUR_HASH_ADAPT */
 		plan->stored_cursor_rec_processed = TRUE;
 
 		btr_pcur_store_position(&(plan->pcur), &mtr);
@@ -2248,8 +2243,9 @@ stop_for_a_while:
 	inserted new records which should have appeared in the result set,
 	which would result in the phantom problem. */
 
-	ut_ad(!search_latch_locked);
-
+#ifdef BTR_CUR_HASH_ADAPT
+	ut_ad(!has_search_latch);
+#endif /* BTR_CUR_HASH_ADAPT */
 	plan->stored_cursor_rec_processed = FALSE;
 	btr_pcur_store_position(&(plan->pcur), &mtr);
 
@@ -2266,7 +2262,9 @@ commit_mtr_for_a_while:
 
 	plan->stored_cursor_rec_processed = TRUE;
 
-	ut_ad(!search_latch_locked);
+#ifdef BTR_CUR_HASH_ADAPT
+	ut_ad(!has_search_latch);
+#endif /* BTR_CUR_HASH_ADAPT */
 	btr_pcur_store_position(&(plan->pcur), &mtr);
 
 	mtr.commit();
@@ -2280,7 +2278,9 @@ lock_wait_or_error:
 	/* See the note at stop_for_a_while: the same holds for this case */
 
 	ut_ad(!btr_pcur_is_before_first_on_page(&plan->pcur) || !node->asc);
-	ut_ad(!search_latch_locked);
+#ifdef BTR_CUR_HASH_ADAPT
+	ut_ad(!has_search_latch);
+#endif /* BTR_CUR_HASH_ADAPT */
 
 	plan->stored_cursor_rec_processed = FALSE;
 	btr_pcur_store_position(&(plan->pcur), &mtr);
@@ -2289,8 +2289,8 @@ lock_wait_or_error:
 
 func_exit:
 #ifdef BTR_CUR_HASH_ADAPT
-	if (search_latch_locked) {
-		btr_search_s_unlock(index);
+	if (has_search_latch) {
+		rw_lock_s_unlock(latch);
 	}
 #endif /* BTR_CUR_HASH_ADAPT */
 	ut_ad(!sync_check_iterate(dict_sync_check()));
@@ -4460,7 +4460,6 @@ row_search_mvcc(
 	    && !prebuilt->templ_contains_blob
 	    && !prebuilt->used_in_HANDLER
 	    && (prebuilt->mysql_row_len < UNIV_PAGE_SIZE / 8)) {
-
 		mode = PAGE_CUR_GE;
 
 		if (trx->mysql_n_tables_locked == 0
@@ -4480,7 +4479,8 @@ row_search_mvcc(
 			and if we try that, we can deadlock on the adaptive
 			hash index semaphore! */
 
-			rw_lock_s_lock(btr_get_search_latch(index));
+			rw_lock_t* const latch = btr_get_search_latch(index);
+			rw_lock_s_lock(latch);
 
 			switch (row_sel_try_search_shortcut_for_mysql(
 					&rec, prebuilt, &offsets, &heap,
@@ -4534,7 +4534,7 @@ row_search_mvcc(
 
 				err = DB_SUCCESS;
 
-				rw_lock_s_unlock(btr_get_search_latch(index));
+				rw_lock_s_unlock(latch);
 
 				goto func_exit;
 
@@ -4544,7 +4544,7 @@ row_search_mvcc(
 
 				err = DB_RECORD_NOT_FOUND;
 
-				rw_lock_s_unlock(btr_get_search_latch(index));
+				rw_lock_s_unlock(latch);
 
 				/* NOTE that we do NOT store the cursor
 				position */
@@ -4561,7 +4561,7 @@ row_search_mvcc(
 			mtr.commit();
 			mtr.start();
 
-                        rw_lock_s_unlock(btr_get_search_latch(index));
+                        rw_lock_s_unlock(latch);
 		}
 	}
 #endif /* BTR_CUR_HASH_ADAPT */
diff --git a/storage/innobase/row/row0trunc.cc b/storage/innobase/row/row0trunc.cc
index 5e512c602e6..618e161bee4 100644
--- a/storage/innobase/row/row0trunc.cc
+++ b/storage/innobase/row/row0trunc.cc
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2013, 2018, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2019, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -39,6 +39,7 @@ Created 2013-04-12 Sunny Bains
 #include "os0file.h"
 #include "que0que.h"
 #include "trx0undo.h"
+#include "btr0sea.h"
 
 /* FIXME: For temporary tables, use a simple approach of btr_free()
 and btr_create() of each index tree. */
@@ -1953,7 +1954,6 @@ dberr_t row_truncate_table_for_mysql(dict_table_t* table, trx_t* trx)
 		for (dict_index_t* index = UT_LIST_GET_FIRST(table->indexes);
 		     index != NULL;
 		     index = UT_LIST_GET_NEXT(indexes, index)) {
-
 			err = dict_truncate_index_tree_in_mem(index);
 
 			if (err != DB_SUCCESS) {
@@ -2003,6 +2003,15 @@ dberr_t row_truncate_table_for_mysql(dict_table_t* table, trx_t* trx)
 			os_thread_sleep(2000000);
 			DBUG_SUICIDE(););
 
+#ifdef BTR_CUR_HASH_ADAPT
+	dict_table_x_unlock_indexes(table);
+	for (dict_index_t* index = UT_LIST_GET_FIRST(table->indexes); index;
+	     index = UT_LIST_GET_NEXT(indexes, index)) {
+		index = index->clone_if_needed();
+	}
+	dict_table_x_lock_indexes(table);
+#endif /* BTR_CUR_HASH_ADAPT */
+
 	/* Step-10: Re-create new indexes. */
 	if (!dict_table_is_temporary(table)) {
 
diff --git a/storage/innobase/trx/trx0purge.cc b/storage/innobase/trx/trx0purge.cc
index 732435ccefb..81ba1b731bf 100644
--- a/storage/innobase/trx/trx0purge.cc
+++ b/storage/innobase/trx/trx0purge.cc
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2017, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2019, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -383,7 +383,7 @@ trx_purge_free_segment(trx_rseg_t* rseg, fil_addr_t hdr_addr)
 		}
 
 		if (fseg_free_step_not_header(
-			    seg_hdr + TRX_UNDO_FSEG_HEADER, false, &mtr)) {
+			    seg_hdr + TRX_UNDO_FSEG_HEADER, &mtr)) {
 
 			break;
 		}
@@ -413,7 +413,7 @@ trx_purge_free_segment(trx_rseg_t* rseg, fil_addr_t hdr_addr)
 		is not flooded with bufferfixed pages: see the note in
 		fsp0fsp.cc. */
 
-	} while (!fseg_free_step(seg_hdr + TRX_UNDO_FSEG_HEADER, false, &mtr));
+	} while (!fseg_free_step(seg_hdr + TRX_UNDO_FSEG_HEADER, &mtr));
 
 	hist_size = mtr_read_ulint(rseg_hdr + TRX_RSEG_HISTORY_SIZE,
 				   MLOG_4BYTES, &mtr);
diff --git a/storage/innobase/trx/trx0undo.cc b/storage/innobase/trx/trx0undo.cc
index 336506c7b65..f9e76e5d772 100644
--- a/storage/innobase/trx/trx0undo.cc
+++ b/storage/innobase/trx/trx0undo.cc
@@ -869,7 +869,7 @@ trx_undo_free_page(
 		    undo_page + TRX_UNDO_PAGE_HDR + TRX_UNDO_PAGE_NODE, mtr);
 
 	fseg_free_page(header_page + TRX_UNDO_SEG_HDR + TRX_UNDO_FSEG_HEADER,
-		       space, page_no, false, mtr);
+		       space, page_no, mtr);
 
 	last_addr = flst_get_last(header_page + TRX_UNDO_SEG_HDR
 				  + TRX_UNDO_PAGE_LIST, mtr);
@@ -1092,7 +1092,7 @@ trx_undo_seg_free(
 
 		file_seg = seg_header + TRX_UNDO_FSEG_HEADER;
 
-		finished = fseg_free_step(file_seg, false, &mtr);
+		finished = fseg_free_step(file_seg, &mtr);
 
 		if (finished) {
 			/* Update the rseg header */