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MDEV-33971 NAME_CONST in WHERE clause replaced by inner item

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Improve performance of queries like
  SELECT * FROM t1 WHERE field = NAME_CONST('a', 4);
by, in this example, replacing the WHERE clause with field = 4
in the case of ref access.

The rewrite is done during fix_fields and we disambiguate this
case from other cases of NAME_CONST by inspecting where we are
in parsing.  We rely on THD::where to accomplish this.  To
improve performance there, we change the type of THD::where to
be an enumeration, so we can avoid string comparisons during
Item_name_const::fix_fields.  Consequently, this patch also
changes all usages of THD::where to conform likewise.
This commit is contained in:
Dave Gosselin
2024-04-26 12:13:31 -04:00
committed by Dave Gosselin
parent a0a7b1c128
commit 02e38e2ece
20 changed files with 310 additions and 75 deletions
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64
sql/sql_class.cc
View File

@@ -83,8 +83,6 @@
char internal_table_name[2]= "*";
char empty_c_string[1]= {0}; /* used for not defined db */
const char * const THD::DEFAULT_WHERE= "field list";
/****************************************************************************
** User variables
****************************************************************************/
@@ -629,6 +627,64 @@ extern "C" void thd_kill_timeout(THD* thd)
thd->awake(KILL_TIMEOUT);
}
const char *thd_where(THD *thd)
{
switch(thd->where) {
case THD_WHERE::CHECKING_TRANSFORMED_SUBQUERY:
return "checking transformed subquery";
break;
case THD_WHERE::IN_ALL_ANY_SUBQUERY:
return "IN/ALL/ANY subquery";
break;
case THD_WHERE::JSON_TABLE_ARGUMENT:
return "JSON_TABLE argument";
break;
case THD_WHERE::DEFAULT_WHERE: // same as FIELD_LIST
case THD_WHERE::FIELD_LIST:
return "field list";
break;
case THD_WHERE::PARTITION_FUNCTION:
return "partition function";
break;
case THD_WHERE::FROM_CLAUSE:
return "from clause";
break;
case THD_WHERE::ON_CLAUSE:
return "on clause";
break;
case THD_WHERE::WHERE_CLAUSE:
return "where clause";
break;
case THD_WHERE::CONVERT_CHARSET_CONST:
return "convert character set partition constant";
break;
case THD_WHERE::FOR_SYSTEM_TIME:
return "FOR SYSTEM_TIME";
break;
case THD_WHERE::ORDER_CLAUSE:
return "order clause";
break;
case THD_WHERE::HAVING_CLAUSE:
return "having clause";
break;
case THD_WHERE::GROUP_STATEMENT:
return "group statement";
break;
case THD_WHERE::PROCEDURE_LIST:
return "procedure list";
break;
case THD_WHERE::CHECK_OPTION:
return "check option";
break;
case THD_WHERE::USE_WHERE_STRING:
return thd->where_str;
default:
break; // "fall-through" to default return below
};
DBUG_ASSERT(false);
return "UNKNOWN";
}
THD::THD(my_thread_id id, bool is_wsrep_applier)
:Statement(&main_lex, &main_mem_root, STMT_CONVENTIONAL_EXECUTION,
/* statement id */ 0),
@@ -838,7 +894,7 @@ THD::THD(my_thread_id id, bool is_wsrep_applier)
/* Variables with default values */
proc_info="login";
where= THD::DEFAULT_WHERE;
where= THD_WHERE::DEFAULT_WHERE;
slave_net = 0;
m_command=COM_CONNECT;
*scramble= '\0';
@@ -2328,7 +2384,7 @@ void THD::cleanup_after_query()
/* Free Items that were created during this execution */
free_items();
/* Reset where. */
where= THD::DEFAULT_WHERE;
where= THD_WHERE::DEFAULT_WHERE;
/* reset table map for multi-table update */
table_map_for_update= 0;
m_binlog_invoker= INVOKER_NONE;