Commit 936688fe authored by unknown's avatar unknown
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A followup patch for Bug#7306 (limit in prepared statements): 

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.
parent 0bc3c622

sql/mysql_priv.h

+2 −0
Original line number Diff line number Diff line
@@ -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

/*

sql/sql_lex.cc

+1 −0
Original line number Diff line number Diff line
@@ -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);

sql/sql_lex.h

+1 −0
Original line number Diff line number Diff line
@@ -303,6 +303,7 @@ class st_select_lex_node { 
      UNCACHEABLE_RAND

      UNCACHEABLE_SIDEEFFECT

      UNCACHEABLE_EXPLAIN

      UNCACHEABLE_PREPARE

  */

  uint8 uncacheable;

  enum sub_select_type linkage;

sql/sql_parse.cc

+8 −6
Original line number Diff line number Diff line
@@ -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);

sql/sql_prepare.cc

+3 −0
Original line number Diff line number Diff line
@@ -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;