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MDEV-20487 Set innodb_adaptive_hash_index=OFF by default

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Based on the performance testing that was conducted in MDEV-17492,
the InnoDB adaptive hash index could only help performance in specific,
almost-read-only workloads. It could slow down all kinds of workloads
(especially DROP TABLE, TRUNCATE TABLE, ALTER TABLE, or DROP INDEX
operations), and it can become corrupted, causing crashes (such as
MDEV-18815, MDEV-20203) and possibly data corruption. Furthermore,
the adaptive hash index consumes space from the InnoDB buffer pool,
which could hurt performance when the working set would almost fit
in the buffer pool.

Given all this, it is best to disable the adaptive hash index by default.
This commit is contained in:
Marko Mäkelä
2019-10-23 17:43:31 +03:00
parent 18a44b4b4b
commit 88cdfc5c7d
3 changed files with 6 additions and 8 deletions
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5
extra/mariabackup/xtrabackup.cc
View File

@@ -1239,11 +1239,10 @@ struct my_option xb_server_options[] =
GET_STR, OPT_ARG, 0, 0, 0, 0, 0, 0},
#ifdef BTR_CUR_HASH_ADAPT
{"innodb_adaptive_hash_index", OPT_INNODB_ADAPTIVE_HASH_INDEX,
"Enable InnoDB adaptive hash index (enabled by default). "
"Disable with --skip-innodb-adaptive-hash-index.",
"Enable InnoDB adaptive hash index (disabled by default).",
&btr_search_enabled,
&btr_search_enabled,
0, GET_BOOL, NO_ARG, 1, 0, 0, 0, 0, 0},
0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
#endif /* BTR_CUR_HASH_ADAPT */
{"innodb_autoextend_increment", OPT_INNODB_AUTOEXTEND_INCREMENT,
"Data file autoextend increment in megabytes",

4
mysql-test/suite/sys_vars/r/sysvars_innodb.result
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@@ -35,10 +35,10 @@ READ_ONLY NO
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME INNODB_ADAPTIVE_HASH_INDEX
SESSION_VALUE NULL
DEFAULT_VALUE ON
DEFAULT_VALUE OFF
VARIABLE_SCOPE GLOBAL
VARIABLE_TYPE BOOLEAN
VARIABLE_COMMENT Enable InnoDB adaptive hash index (enabled by default). Disable with --skip-innodb-adaptive-hash-index.
VARIABLE_COMMENT Enable InnoDB adaptive hash index (disabled by default).
NUMERIC_MIN_VALUE NULL
NUMERIC_MAX_VALUE NULL
NUMERIC_BLOCK_SIZE NULL

5
storage/innobase/handler/ha_innodb.cc
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@@ -18744,9 +18744,8 @@ static MYSQL_SYSVAR_BOOL(stats_traditional, srv_stats_sample_traditional,
#ifdef BTR_CUR_HASH_ADAPT
static MYSQL_SYSVAR_BOOL(adaptive_hash_index, btr_search_enabled,
PLUGIN_VAR_OPCMDARG,
"Enable InnoDB adaptive hash index (enabled by default). "
" Disable with --skip-innodb-adaptive-hash-index.",
NULL, innodb_adaptive_hash_index_update, true);
"Enable InnoDB adaptive hash index (disabled by default).",
NULL, innodb_adaptive_hash_index_update, false);
/** Number of distinct partitions of AHI.
Each partition is protected by its own latch and so we have parts number