Bug #56680 wrong InnoDB results from a case-insensitive covering index

row_search_for_mysql(): When a secondary index record might not be
visible in the current transaction's read view and we consult the
clustered index and optionally some undo log records, return the
relevant columns of the clustered index record to MySQL instead of the
secondary index record.

REC_INFO_DELETED_FLAG: Move the definition from rem0rec.ic to rem0rec.h.

ibuf_insert_to_index_page_low(): New function, refactored from
ibuf_insert_to_index_page().

ibuf_insert_to_index_page(): When we are inserting a record in place
of a delete-marked record and some fields of the record differ, update
that record just like row_ins_sec_index_entry_by_modify() would do.

mysql_row_templ_t: Add clust_rec_field_no.

row_sel_store_mysql_rec(), row_sel_push_cache_row_for_mysql(): Add the
flag rec_clust, for returning data at clust_rec_field_no instead of
rec_field_no. Resurrect the debug assertion that the record not be
marked for deletion. (Bug #55626)

buf_LRU_free_block(): Refactored from
buf_LRU_search_and_free_block(). This is needed for the
innodb_change_buffering_debug diagnostics.

[UNIV_DEBUG || UNIV_IBUF_DEBUG] ibuf_debug, buf_page_get_gen(),
buf_flush_page_try():
Implement innodb_change_buffering_debug=1 for evicting pages from the
buffer pool, so that change buffering will be attempted more
frequently.

2 files changed, 232 insertions, 0 deletions

diff --git a/mysql-test/suite/innodb/r/innodb_bug56680.result b/mysql-test/suite/innodb/r/innodb_bug56680.result
new file mode 100644
index 00000000000..c3afc3e6581
--- /dev/null
+++ b/mysql-test/suite/innodb/r/innodb_bug56680.result
@@ -0,0 +1,102 @@
+SET GLOBAL tx_isolation='REPEATABLE-READ';
+CREATE TABLE bug56680(
+a INT AUTO_INCREMENT PRIMARY KEY,
+b CHAR(1),
+c INT,
+INDEX(b))
+ENGINE=InnoDB;
+INSERT INTO bug56680 VALUES(0,'x',1);
+BEGIN;
+SELECT b FROM bug56680;
+b
+x
+BEGIN;
+UPDATE bug56680 SET b='X';
+SELECT b FROM bug56680;
+b
+x
+SELECT * FROM bug56680;
+a	b	c
+1	x	1
+ROLLBACK;
+SELECT b FROM bug56680;
+b
+x
+SET GLOBAL tx_isolation='READ-UNCOMMITTED';
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+BEGIN;
+SELECT b FROM bug56680 LIMIT 2;
+b
+x
+x
+BEGIN;
+DELETE FROM bug56680 WHERE a=1;
+INSERT INTO bug56680 VALUES(1,'X',1);
+SELECT b FROM bug56680 LIMIT 3;
+b
+X
+x
+x
+SELECT b FROM bug56680 LIMIT 2;
+b
+x
+x
+CHECK TABLE bug56680;
+Table	Op	Msg_type	Msg_text
+test.bug56680	check	status	OK
+ROLLBACK;
+SELECT b FROM bug56680 LIMIT 2;
+b
+x
+x
+CHECK TABLE bug56680;
+Table	Op	Msg_type	Msg_text
+test.bug56680	check	status	OK
+SELECT b FROM bug56680 LIMIT 2;
+b
+x
+x
+CREATE TABLE bug56680_2(
+a INT AUTO_INCREMENT PRIMARY KEY,
+b VARCHAR(2) CHARSET latin1 COLLATE latin1_german2_ci,
+c INT,
+INDEX(b))
+ENGINE=InnoDB;
+INSERT INTO bug56680_2 SELECT 0,_latin1 0xdf,c FROM bug56680;
+BEGIN;
+SELECT HEX(b) FROM bug56680_2 LIMIT 2;
+HEX(b)
+DF
+DF
+DELETE FROM bug56680_2 WHERE a=1;
+INSERT INTO bug56680_2 VALUES(1,'SS',1);
+SELECT HEX(b) FROM bug56680_2 LIMIT 3;
+HEX(b)
+5353
+DF
+DF
+CHECK TABLE bug56680_2;
+Table	Op	Msg_type	Msg_text
+test.bug56680_2	check	status	OK
+DELETE FROM bug56680_2 WHERE a=1;
+INSERT INTO bug56680_2 VALUES(1,_latin1 0xdf,1);
+SELECT HEX(b) FROM bug56680_2 LIMIT 3;
+HEX(b)
+DF
+DF
+DF
+CHECK TABLE bug56680_2;
+Table	Op	Msg_type	Msg_text
+test.bug56680_2	check	status	OK
+DROP TABLE bug56680_2;
+DROP TABLE bug56680;
diff --git a/mysql-test/suite/innodb/t/innodb_bug56680.test b/mysql-test/suite/innodb/t/innodb_bug56680.test
new file mode 100644
index 00000000000..ab81ca2f8e6
--- /dev/null
+++ b/mysql-test/suite/innodb/t/innodb_bug56680.test
@@ -0,0 +1,130 @@
+#
+# Bug #56680 InnoDB may return wrong results from a case-insensitive index
+#
+-- source include/have_innodb.inc
+
+-- disable_query_log
+SET @tx_isolation_orig = @@tx_isolation;
+# The flag innodb_change_buffering_debug is only available in debug builds.
+# It instructs InnoDB to try to evict pages from the buffer pool when
+# change buffering is possible, so that the change buffer will be used
+# whenever possible.
+-- error 0,ER_UNKNOWN_SYSTEM_VARIABLE
+SET @innodb_change_buffering_debug_orig = @@innodb_change_buffering_debug;
+-- error 0,ER_UNKNOWN_SYSTEM_VARIABLE
+SET GLOBAL innodb_change_buffering_debug = 1;
+-- enable_query_log
+SET GLOBAL tx_isolation='REPEATABLE-READ';
+
+CREATE TABLE bug56680(
+       a INT AUTO_INCREMENT PRIMARY KEY,
+       b CHAR(1),
+       c INT,
+       INDEX(b))
+ENGINE=InnoDB;
+
+INSERT INTO bug56680 VALUES(0,'x',1);
+BEGIN;
+SELECT b FROM bug56680;
+
+connect (con1,localhost,root,,);
+connection con1;
+BEGIN;
+UPDATE bug56680 SET b='X';
+
+connection default;
+# This should return the last committed value 'x', but would return 'X'
+# due to a bug in row_search_for_mysql().
+SELECT b FROM bug56680;
+# This would always return the last committed value 'x'.
+SELECT * FROM bug56680;
+
+connection con1;
+ROLLBACK;
+disconnect con1;
+
+connection default;
+
+SELECT b FROM bug56680;
+
+# For the rest of this test, use the READ UNCOMMITTED isolation level
+# to see what exists in the secondary index.
+SET GLOBAL tx_isolation='READ-UNCOMMITTED';
+
+# Create enough rows for the table, so that the insert buffer will be
+# used for modifying the secondary index page. There must be multiple
+# index pages, because changes to the root page are never buffered.
+
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+INSERT INTO bug56680 SELECT 0,b,c FROM bug56680;
+
+BEGIN;
+SELECT b FROM bug56680 LIMIT 2;
+
+connect (con1,localhost,root,,);
+connection con1;
+BEGIN;
+DELETE FROM bug56680 WHERE a=1;
+# This should be buffered, if innodb_change_buffering_debug = 1 is in effect.
+INSERT INTO bug56680 VALUES(1,'X',1);
+
+# This should force an insert buffer merge, and return 'X' in the first row.
+SELECT b FROM bug56680 LIMIT 3;
+
+connection default;
+SELECT b FROM bug56680 LIMIT 2;
+CHECK TABLE bug56680;
+
+connection con1;
+ROLLBACK;
+SELECT b FROM bug56680 LIMIT 2;
+CHECK TABLE bug56680;
+
+connection default;
+disconnect con1;
+
+SELECT b FROM bug56680 LIMIT 2;
+
+CREATE TABLE bug56680_2(
+       a INT AUTO_INCREMENT PRIMARY KEY,
+       b VARCHAR(2) CHARSET latin1 COLLATE latin1_german2_ci,
+       c INT,
+       INDEX(b))
+ENGINE=InnoDB;
+
+INSERT INTO bug56680_2 SELECT 0,_latin1 0xdf,c FROM bug56680;
+
+BEGIN;
+SELECT HEX(b) FROM bug56680_2 LIMIT 2;
+DELETE FROM bug56680_2 WHERE a=1;
+# This should be buffered, if innodb_change_buffering_debug = 1 is in effect.
+INSERT INTO bug56680_2 VALUES(1,'SS',1);
+
+# This should force an insert buffer merge, and return 'SS' in the first row.
+SELECT HEX(b) FROM bug56680_2 LIMIT 3;
+CHECK TABLE bug56680_2;
+
+DELETE FROM bug56680_2 WHERE a=1;
+# This should be buffered, if innodb_change_buffering_debug = 1 is in effect.
+INSERT INTO bug56680_2 VALUES(1,_latin1 0xdf,1);
+
+# This should force an insert buffer merge, and return 0xdf in the first row.
+SELECT HEX(b) FROM bug56680_2 LIMIT 3;
+CHECK TABLE bug56680_2;
+
+DROP TABLE bug56680_2;
+DROP TABLE bug56680;
+
+-- disable_query_log
+SET GLOBAL tx_isolation = @tx_isolation_orig;
+-- error 0, ER_UNKNOWN_SYSTEM_VARIABLE
+SET GLOBAL innodb_change_buffering_debug = @innodb_change_buffering_debug_orig;