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A followup patch for Bug#7306 (limit in prepared statements):

Browse source 
don't evaluate subqueries during statement prepare, even if they
are not correlated.
With post-review fixes.


sql/mysql_priv.h:
  Add UNCACHEABLE_PREPARE to mark subqueries as non-constant in 
  mysql_stmt_prepare
sql/sql_lex.cc:
  Add a missing assert: noone can call unit::set_limit from 
  mysql_stmt_prepare.
sql/sql_lex.h:
  Comment fixed.
sql/sql_parse.cc:
  Mark new SELECT_LEXes as uncacheable if they created during 
  statement prepare.
sql/sql_prepare.cc:
  Switch off the uncacheable flag when prepare is done.
This commit is contained in:
unknown 2005-06-08 00:34:53 +04:00
parent 0bc3c6221c
commit 936688feb5
5 changed files with 15 additions and 6 deletions
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2
sql/mysql_priv.h
View file

@ -336,6 +336,8 @@ extern CHARSET_INFO *national_charset_info, *table_alias_charset;
#define UNCACHEABLE_SIDEEFFECT 4
// forcing to save JOIN for explain
#define UNCACHEABLE_EXPLAIN 8
/* Don't evaluate subqueries in prepare even if they're not correlated */
#define UNCACHEABLE_PREPARE 16
#ifdef EXTRA_DEBUG
/*

1
sql/sql_lex.cc
View file

@ -1757,6 +1757,7 @@ void st_select_lex_unit::set_limit(SELECT_LEX *sl)
{
ulonglong select_limit_val;
DBUG_ASSERT(! thd->current_arena->is_stmt_prepare());
select_limit_val= sl->select_limit ? sl->select_limit->val_uint() :
HA_POS_ERROR;
offset_limit_cnt= sl->offset_limit ? sl->offset_limit->val_uint() : ULL(0);

1
sql/sql_lex.h
View file

@ -303,6 +303,7 @@ public:
UNCACHEABLE_RAND
UNCACHEABLE_SIDEEFFECT
UNCACHEABLE_EXPLAIN
UNCACHEABLE_PREPARE
*/
uint8 uncacheable;
enum sub_select_type linkage;

14
sql/sql_parse.cc
View file

@ -5169,26 +5169,28 @@ bool
mysql_new_select(LEX *lex, bool move_down)
{
SELECT_LEX *select_lex;
THD *thd;
THD *thd= lex->thd;
DBUG_ENTER("mysql_new_select");
if (!(select_lex= new(lex->thd->mem_root) SELECT_LEX()))
if (!(select_lex= new (thd->mem_root) SELECT_LEX()))
DBUG_RETURN(1);
select_lex->select_number= ++lex->thd->select_number;
select_lex->select_number= ++thd->select_number;
select_lex->init_query();
select_lex->init_select();
select_lex->parent_lex= lex;
if (thd->current_arena->is_stmt_prepare())
select_lex->uncacheable|= UNCACHEABLE_PREPARE;
if (move_down)
{
SELECT_LEX_UNIT *unit;
lex->subqueries= TRUE;
/* first select_lex of subselect or derived table */
if (!(unit= new(lex->thd->mem_root) SELECT_LEX_UNIT()))
if (!(unit= new (thd->mem_root) SELECT_LEX_UNIT()))
DBUG_RETURN(1);
unit->init_query();
unit->init_select();
unit->thd= lex->thd;
unit->thd= thd;
unit->include_down(lex->current_select);
unit->link_next= 0;
unit->link_prev= 0;
@ -5212,7 +5214,7 @@ mysql_new_select(LEX *lex, bool move_down)
as far as we included SELECT_LEX for UNION unit should have
fake SELECT_LEX for UNION processing
*/
if (!(fake= unit->fake_select_lex= new(lex->thd->mem_root) SELECT_LEX()))
if (!(fake= unit->fake_select_lex= new (thd->mem_root) SELECT_LEX()))
DBUG_RETURN(1);
fake->include_standalone(unit,
(SELECT_LEX_NODE**)&unit->fake_select_lex);

3
sql/sql_prepare.cc
View file

@ -1838,7 +1838,10 @@ void init_stmt_after_parse(THD *thd, LEX *lex)
optimisation.
*/
for (; sl; sl= sl->next_select_in_list())
{
sl->prep_where= sl->where;
sl->uncacheable&= ~UNCACHEABLE_PREPARE;
}
for (TABLE_LIST *table= lex->query_tables; table; table= table->next_global)
table->prep_on_expr= table->on_expr;