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MDEV-10649: Optimizer sometimes use "index" instead of "range" access for UPDATE

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(Fixing both InnoDB and XtraDB)

Re-opening a TABLE object (after e.g. FLUSH TABLES or open table cache
eviction) causes ha_innobase to call
dict_stats_update(DICT_STATS_FETCH_ONLY_IF_NOT_IN_MEMORY).

Inside this call, the following is done:
  dict_stats_empty_table(table);
  dict_stats_copy(table, t);

On the other hand, commands like UPDATE make this call to get the "rows in
table" statistics in table->stats.records:

  ha_innobase->info(HA_STATUS_VARIABLE|HA_STATUS_NO_LOCK)

note the HA_STATUS_NO_LOCK parameter. It means, no locks are taken by
::info() If the ::info() call happens between dict_stats_empty_table
and dict_stats_copy calls, the UPDATE's optimizer will get an estimate
of table->stats.records=1, which causes it to pick a full table scan,
which in turn will take a lot of row locks and cause other bad
consequences.
This commit is contained in:
Sergei Petrunia 2016-09-28 16:12:58 +03:00
parent 5bbe929d70
commit a53f3c6d3c
2 changed files with 38 additions and 20 deletions
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29
storage/innobase/dict/dict0stats.cc
View File

@ -673,7 +673,10 @@ void
dict_stats_copy(
/*============*/
dict_table_t* dst, /*!< in/out: destination table */
const dict_table_t* src) /*!< in: source table */
const dict_table_t* src, /*!< in: source table */
bool reset_ignored_indexes) /*!< in: if true, set ignored indexes
to have the same statistics as if
the table was empty */
{
dst->stats_last_recalc = src->stats_last_recalc;
dst->stat_n_rows = src->stat_n_rows;
@ -692,7 +695,16 @@ dict_stats_copy(
&& (src_idx = dict_table_get_next_index(src_idx)))) {
if (dict_stats_should_ignore_index(dst_idx)) {
continue;
if (reset_ignored_indexes) {
/* Reset index statistics for all ignored indexes,
unless they are FT indexes (these have no statistics)*/
if (dst_idx->type & DICT_FTS) {
continue;
}
dict_stats_empty_index(dst_idx);
} else {
continue;
}
}
ut_ad(!dict_index_is_univ(dst_idx));
@ -782,7 +794,7 @@ dict_stats_snapshot_create(
t = dict_stats_table_clone_create(table);
dict_stats_copy(t, table);
dict_stats_copy(t, table, false);
t->stat_persistent = table->stat_persistent;
t->stats_auto_recalc = table->stats_auto_recalc;
@ -3240,13 +3252,10 @@ dict_stats_update(
dict_table_stats_lock(table, RW_X_LATCH);
/* Initialize all stats to dummy values before
copying because dict_stats_table_clone_create() does
skip corrupted indexes so our dummy object 't' may
have less indexes than the real object 'table'. */
dict_stats_empty_table(table);
dict_stats_copy(table, t);
/* Pass reset_ignored_indexes=true as parameter
to dict_stats_copy. This will cause statictics
for corrupted indexes to be set to empty values */
dict_stats_copy(table, t, true);
dict_stats_assert_initialized(table);

29
storage/xtradb/dict/dict0stats.cc
View File

@ -673,7 +673,10 @@ void
dict_stats_copy(
/*============*/
dict_table_t* dst, /*!< in/out: destination table */
const dict_table_t* src) /*!< in: source table */
const dict_table_t* src, /*!< in: source table */
bool reset_ignored_indexes) /*!< in: if true, set ignored indexes
to have the same statistics as if
the table was empty */
{
dst->stats_last_recalc = src->stats_last_recalc;
dst->stat_n_rows = src->stat_n_rows;
@ -692,7 +695,16 @@ dict_stats_copy(
&& (src_idx = dict_table_get_next_index(src_idx)))) {
if (dict_stats_should_ignore_index(dst_idx)) {
continue;
if (reset_ignored_indexes) {
/* Reset index statistics for all ignored indexes,
unless they are FT indexes (these have no statistics)*/
if (dst_idx->type & DICT_FTS) {
continue;
}
dict_stats_empty_index(dst_idx);
} else {
continue;
}
}
ut_ad(!dict_index_is_univ(dst_idx));
@ -782,7 +794,7 @@ dict_stats_snapshot_create(
t = dict_stats_table_clone_create(table);
dict_stats_copy(t, table);
dict_stats_copy(t, table, false);
t->stat_persistent = table->stat_persistent;
t->stats_auto_recalc = table->stats_auto_recalc;
@ -3240,13 +3252,10 @@ dict_stats_update(
dict_table_stats_lock(table, RW_X_LATCH);
/* Initialize all stats to dummy values before
copying because dict_stats_table_clone_create() does
skip corrupted indexes so our dummy object 't' may
have less indexes than the real object 'table'. */
dict_stats_empty_table(table);
dict_stats_copy(table, t);
/* Pass reset_ignored_indexes=true as parameter
to dict_stats_copy. This will cause statictics
for corrupted indexes to be set to empty values */
dict_stats_copy(table, t, true);
dict_stats_assert_initialized(table);