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.

1 files changed, 8 insertions, 39 deletions

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.