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MDEV-34888 Implement SEMIJOIN() and SUBQUERY() hints

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This commit is contained in:
Oleg Smirnov
2024-09-11 19:53:57 +07:00
parent e3bf4c826c
commit 2c8f6058c1
28 changed files with 3712 additions and 164 deletions
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80
sql/sql_lex.cc
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@@ -38,7 +38,7 @@
#include "sql_partition.h"
#include "sql_partition_admin.h" // Sql_cmd_alter_table_*_part
#include "event_parse_data.h"
#include "opt_hints_parser.h"
#include "opt_hints.h"
#ifdef WITH_WSREP
#include "mysql/service_wsrep.h"
#endif
@@ -5984,6 +5984,84 @@ bool st_select_lex::is_merged_child_of(st_select_lex *ancestor)
return all_merged;
}
/**
Returns which subquery execution strategies can be used for this query block.
@param thd Pointer to THD object for session.
Used to access optimizer_switch
@retval SUBS_MATERIALIZATION Subquery Materialization should be used
@retval SUBS_IN_TO_EXISTS In-to-exists execution should be used
@retval SUBS_MATERIALIZATION | SUBS_IN_TO_EXISTS A cost-based decision
should be made
*/
uint st_select_lex::subquery_strategies_allowed(THD *thd) const
{
if (opt_hints_qb && opt_hints_qb->subquery_strategy != SUBS_NOT_TRANSFORMED)
return opt_hints_qb->subquery_strategy;
// No SUBQUERY hint given, base possible strategies on optimizer_switch
uint strategy = SUBS_NOT_TRANSFORMED;
if (optimizer_flag(thd, OPTIMIZER_SWITCH_MATERIALIZATION))
strategy |= SUBS_MATERIALIZATION;
if (optimizer_flag(thd, OPTIMIZER_SWITCH_IN_TO_EXISTS))
strategy |= SUBS_IN_TO_EXISTS;
return strategy;
}
/**
Returns whether semi-join is enabled for this query block
@see @c Opt_hints_qb::semijoin_enabled for details on how hints
affect this decision. If there are no hints for this query block,
optimizer_switch setting determines whether semi-join is used.
@param thd Pointer to THD object for session.
Used to access optimizer_switch
@return true if semijoin is enabled,
false otherwise
*/
bool st_select_lex::semijoin_enabled(THD *thd) const
{
return opt_hints_qb ?
opt_hints_qb->semijoin_enabled(thd) :
optimizer_flag(thd, OPTIMIZER_SWITCH_SEMIJOIN);
}
/**
Update available semijoin strategies for semijoin nests.
Available semijoin strategies needs to be updated on every execution since
optimizer_switch setting may have changed.
@param thd Pointer to THD object for session.
Used to access optimizer_switch
*/
void st_select_lex::update_available_semijoin_strategies(THD *thd)
{
uint sj_strategy_mask= OPTIMIZER_SWITCH_FIRSTMATCH |
OPTIMIZER_SWITCH_LOOSE_SCAN | OPTIMIZER_SWITCH_MATERIALIZATION |
OPTIMIZER_SWITCH_DUPSWEEDOUT;
uint opt_switches= thd->variables.optimizer_switch & sj_strategy_mask;
List_iterator<TABLE_LIST> sj_list_it(sj_nests);
TABLE_LIST *sj_nest;
while ((sj_nest= sj_list_it++))
{
/*
After semi-join transformation, original SELECT_LEX with hints is lost.
Fetch hints from first table in semijoin nest.
*/
List_iterator<TABLE_LIST> table_list(sj_nest->nested_join->join_list);
TABLE_LIST *table= table_list++;
sj_nest->nested_join->sj_enabled_strategies= table->opt_hints_qb ?
table->opt_hints_qb->sj_enabled_strategies(opt_switches) : opt_switches;
}
}
/*
This is used by SHOW EXPLAIN|ANALYZE. It assumes query plan has been already
collected into QPF structures and we only need to print it out.