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Simplified away statistics_for_tables_is_needed()

Browse Source 
Removed redundant loops, integrated logics into the caller instead.
Unified condition in read_statistics_for_tables(), less
"table_share != NULL" checks, no more potential "table_share == NULL"
dereferencing.

Part of MDEV-19061 - table_share used for reading statistical tables is
                     not protected
This commit is contained in:
Sergey Vojtovich
2019-10-11 17:20:28 +04:00
parent a2932e86b5
commit 1055a7f4fc
1 changed files with 31 additions and 81 deletions
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112
sql/sql_statistics.cc
View File

@ -3035,71 +3035,6 @@ void delete_stat_values_for_table_share(TABLE_SHARE *table_share)
}
/**
@brief
Check whether any statistics is to be read for tables from a table list
@param
thd The thread handle
@param
tables The tables list for whose tables the check is to be done
@details
The function checks whether for any of the tables opened and locked for
a statement statistics from statistical tables is needed to be read.
@retval
TRUE statistics for any of the tables is needed to be read
@retval
FALSE Otherwise
*/
static
bool statistics_for_tables_is_needed(THD *thd, TABLE_LIST *tables)
{
if (!tables)
return FALSE;
/*
Do not read statistics for any query that explicity involves
statistical tables, failure to to do so we may end up
in a deadlock.
*/
for (TABLE_LIST *tl= tables; tl; tl= tl->next_global)
{
if (!tl->is_view_or_derived() && !is_temporary_table(tl) && tl->table)
{
TABLE_SHARE *table_share= tl->table->s;
if (table_share &&
table_share->table_category != TABLE_CATEGORY_USER
&& is_stat_table(tl->db, tl->alias))
return FALSE;
}
}
for (TABLE_LIST *tl= tables; tl; tl= tl->next_global)
{
if (!tl->is_view_or_derived() && !is_temporary_table(tl) && tl->table)
{
TABLE_SHARE *table_share= tl->table->s;
if (table_share &&
table_share->stats_cb.stats_can_be_read &&
(!table_share->stats_cb.stats_is_read ||
(!table_share->stats_cb.histograms_are_read &&
thd->variables.optimizer_use_condition_selectivity > 3)))
return TRUE;
if (table_share->stats_cb.stats_is_read)
tl->table->stats_is_read= TRUE;
if (table_share->stats_cb.histograms_are_read)
tl->table->histograms_are_read= TRUE;
}
}
return FALSE;
}
/**
@brief
Read histogram for a table from the persistent statistical tables
@ -3221,13 +3156,16 @@ int read_statistics_for_tables(THD *thd, TABLE_LIST *tables)
if (thd->bootstrap || thd->variables.use_stat_tables == NEVER)
DBUG_RETURN(0);
bool found_stat_table= false;
bool statistics_for_tables_is_needed= false;
for (TABLE_LIST *tl= tables; tl; tl= tl->next_global)
{
if (tl->table)
TABLE_SHARE *table_share;
if (!tl->is_view_or_derived() && tl->table && (table_share= tl->table->s) &&
table_share->tmp_table == NO_TMP_TABLE)
{
TABLE_SHARE *table_share= tl->table->s;
if (table_share && table_share->table_category == TABLE_CATEGORY_USER &&
table_share->tmp_table == NO_TMP_TABLE)
if (table_share->table_category == TABLE_CATEGORY_USER)
{
if (table_share->stats_cb.stats_can_be_read ||
!alloc_statistics_for_table_share(thd, table_share))
@ -3244,15 +3182,29 @@ int read_statistics_for_tables(THD *thd, TABLE_LIST *tables)
for ( ; *field_ptr; field_ptr++, table_field_ptr++)
(*table_field_ptr)->read_stats= (*field_ptr)->read_stats;
tl->table->stats_is_read= table_share->stats_cb.stats_is_read;
tl->table->histograms_are_read=
table_share->stats_cb.histograms_are_read;
if (!tl->table->stats_is_read ||
(!table_share->stats_cb.histograms_are_read &&
thd->variables.optimizer_use_condition_selectivity > 3))
statistics_for_tables_is_needed= true;
}
}
}
else if (is_stat_table(tl->db, tl->alias))
found_stat_table= true;
}
}
DEBUG_SYNC(thd, "statistics_read_start");
if (!statistics_for_tables_is_needed(thd, tables))
/*
Do not read statistics for any query that explicity involves
statistical tables, failure to to do so we may end up
in a deadlock.
*/
if (found_stat_table || !statistics_for_tables_is_needed)
DBUG_RETURN(0);
if (open_stat_tables(thd, stat_tables, &open_tables_backup, FALSE))
@ -3260,14 +3212,12 @@ int read_statistics_for_tables(THD *thd, TABLE_LIST *tables)
for (TABLE_LIST *tl= tables; tl; tl= tl->next_global)
{
if (!tl->is_view_or_derived() && !is_temporary_table(tl) && tl->table)
{
TABLE_SHARE *table_share= tl->table->s;
if (table_share && !(table_share->table_category == TABLE_CATEGORY_USER))
continue;
if (table_share &&
table_share->stats_cb.stats_can_be_read &&
TABLE_SHARE *table_share;
if (!tl->is_view_or_derived() && tl->table && (table_share= tl->table->s) &&
table_share->tmp_table == NO_TMP_TABLE &&
table_share->table_category == TABLE_CATEGORY_USER)
{
if (table_share->stats_cb.stats_can_be_read &&
!table_share->stats_cb.stats_is_read)
{
(void) read_statistics_for_table(thd, tl->table, stat_tables);
@ -3275,8 +3225,8 @@ int read_statistics_for_tables(THD *thd, TABLE_LIST *tables)
}
if (table_share->stats_cb.stats_is_read)
tl->table->stats_is_read= TRUE;
if (thd->variables.optimizer_use_condition_selectivity > 3 &&
table_share && table_share->stats_cb.stats_can_be_read &&
if (thd->variables.optimizer_use_condition_selectivity > 3 &&
table_share->stats_cb.stats_can_be_read &&
!table_share->stats_cb.histograms_are_read)
{
(void) read_histograms_for_table(thd, tl->table, stat_tables);
@ -3285,7 +3235,7 @@ int read_statistics_for_tables(THD *thd, TABLE_LIST *tables)
if (table_share->stats_cb.histograms_are_read)
tl->table->histograms_are_read= TRUE;
}
}
}
close_system_tables(thd, &open_tables_backup);