MDEV-29694 fixup: Remove srv_change_buffer_max_size, adjust comments

mysql-test/suite/innodb_zip/t/page_size.test

@@ -728,29 +728,6 @@ SHOW WARNINGS;
 ROLLBACK;
 DROP TABLE bug12547647;
 
-#
-# Bug #13336585 - INNODB: CHANGE BUFFERING WITH 4K PAGES CAN ASSERT
-#                 IF SECONDARY KEY IS NEAR MAX
-# If the secondary index tuple is close to half the page size,
-# ibuf_insert_low() could return DB_TOO_BIG_RECORD, which is not expected
-# in ibuf_insert().  In order to insure this does not happen, WL5756
-# imposes a maximum key length of 768 for 4k pages and 1536 for 8k pages.
-# The existing max key Size for 16k pages is 3072.
-#
-
-#-- disable_query_log
-# 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.
-# This flag is not used currently since it exposes valgrind error in ibuf
-# code with the following SQL
-#-- 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
-
 # make sure the largest possible key entry can be added to the insert buffer.
 # Make enough records so that the root page is not a leaf page.
 SET SESSION innodb_strict_mode = OFF;
@@ -823,11 +800,6 @@ INSERT INTO t1 VALUES(@r,@r,@r,@r,@r,@r,@r,@r,@r,@r,@r,@r,@r,@r,@r,@r,
 DELETE from t1;
 DROP TABLE t1;
 
-#-- disable_query_log
-#-- error 0,ER_UNKNOWN_SYSTEM_VARIABLE
-#SET GLOBAL innodb_change_buffering_debug = 0;
-#-- enable_query_log
-
 # The following should fail in non-strict mode too.
 # (The fix of Bug #50945 only affects REDUNDANT and COMPACT tables.)
 if ($INNODB_PAGE_SIZE == 4096)

mysql-test/suite/perfschema/t/show_sanity.test

@@ -400,9 +400,6 @@ insert into test.sanity values
   ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_BUFFER_POOL_LOAD_NOW"),
   ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_BUFFER_POOL_SIZE"),
   ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_BUF_FLUSH_LIST_NOW"),
-  ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_CHANGE_BUFFERING"),
-  ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_CHANGE_BUFFERING_DEBUG"),
-  ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_CHANGE_BUFFER_MAX_SIZE"),
   ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_CHECKSUM_ALGORITHM"),
   ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_CMP_PER_INDEX_ENABLED"),
   ("JUNK: GLOBAL-ONLY", "I_S.SESSION_VARIABLES", "INNODB_COMPRESS_DEBUG"),

storage/innobase/include/srv0srv.h

@@ -275,8 +275,6 @@ extern double	srv_defragment_fill_factor;
 extern uint	srv_defragment_frequency;
 extern ulonglong	srv_defragment_interval;
 
-extern uint	srv_change_buffer_max_size;
-
 /* Number of IO operations per second the server can do */
 extern ulong    srv_io_capacity;
 
@@ -301,7 +299,7 @@ extern ulong	srv_flushing_avg_loops;
 
 extern ulong	srv_force_recovery;
 
-/** innodb_fast_shutdown=1 skips purge and change buffer merge.
+/** innodb_fast_shutdown=1 skips purge.
 innodb_fast_shutdown=2 effectively crashes the server (no log checkpoint).
 innodb_fast_shutdown=3 is a clean shutdown that skips the rollback
 of active transaction (to be done on restart). */

storage/innobase/log/log0recv.cc

@@ -3011,9 +3011,7 @@ static buf_block_t *recv_recover_page(buf_block_t *block, mtr_t &mtr,
 		mysql_mutex_unlock(&buf_pool.flush_list_mutex);
 	} else if (free_page && init_lsn) {
 		/* There have been no operations that modify the page.
-		Any buffered changes must not be merged. A subsequent
-		buf_page_create() from a user thread should discard
-		any buffered changes. */
+		Any buffered changes will be merged in ibuf_upgrade(). */
 		ut_ad(!mtr.has_modifications());
 		block->page.set_freed(block->page.state());
 	}

storage/innobase/srv/srv0srv.cc

@@ -218,10 +218,6 @@ in the buffer cache and accessed sequentially for InnoDB to trigger a
 readahead request. */
 ulong	srv_read_ahead_threshold;
 
-/** innodb_change_buffer_max_size; maximum on-disk size of change
-buffer in terms of percentage of the buffer pool. */
-uint	srv_change_buffer_max_size;
-
 /** copy of innodb_open_files; @see innodb_init_params() */
 ulint	srv_max_n_open_files;