Preparatory (and the most problematic) patch for Bug#7306

"the server side preparedStatement error for LIMIT placeholder",
which moves all uses of LIMIT clause from PREPARE to OPTIMIZE
and later steps.
After-review fixes.


mysql-test/r/group_min_max.result:
  Test results fixed for EXPLAINs when using GROUP_MIN_MAX access plan.
sql/item_subselect.cc:
  Move setting of the internal LIMIT used for IN/ALL/ANY/EXISTS 
  subqueries to one place: Item_exists_subselect::fix_length_and_dec().
  This implies that unit->select_limit_cnt is not set until the item is 
  fixed. This is OK, as now LIMIT values are not used until JOIN::optimize.
sql/mysql_priv.h:
  setup_tables no longer needs a special flag for the case when
  it's called from JOIN::reinit() (we don't need to call setup_tables
  between two executions of a correlated subquery).
sql/opt_range.cc:
  Fix a glitch in GROUP_MIN_MAX access plan: we should use table metadata,
  not field data, to evaluate max_used_key_length, which is then
  used for explain.
sql/sp.cc:
  - setup_tables signature changed.
sql/sql_base.cc:
  - setup_tables no longer needs a special mode for subqueries.
    Unused checks were removed.
sql/sql_delete.cc:
  - setup_tables signature changed
sql/sql_help.cc:
  - setup_tables signature changed
sql/sql_insert.cc:
  - setup_tables signature changed
sql/sql_lex.cc:
  Consolidate setting of internal LIMIT for IN/ALL/ANY/EXISTS subqeries
  in one place, and hence remove it from st_select_lex::test_limit().
sql/sql_lex.h:
  Cleanup signature of st_select_lex_unit::init_prepare_fake_select_lex().
sql/sql_load.cc:
  - setup_tables signature changed
sql/sql_olap.cc:
  - setup_tables signature changed
sql/sql_parse.cc:
  - st_select_lex_unit::set_limit() signature changed
sql/sql_select.cc:
  Move setting of JOIN::select_limit from JOIN::prepare
  to JOIN::optimize. At prepare, limit is unknown yet.
  Remove excessive cleanups from JOIN::reinit which were overwriting
  join->join_tab[i]->table->used_keys. This fixes the bug which was triggered
  by the change in item_subselect.cc.
sql/sql_union.cc:
  Class st_select_lex_unit was changed to avoid calls to 
   st_select_lex_unit::set_limit from places where it may be unknown.
  Now unit->select_limit_cnt is set at ::exec(). 
  st_select_lex_unit::init_prepare_fake_select_lex(): 
   - move out set_limit functionality
   - remove a few lines of dead code.
  st_select_lex_unit::prepare():
    - now we don't call set_limit at the time of prepare, so the value  
      of unit->select_limit_cnt may be unknown here. Use sl->select_limit
      instead.
  st_select_lex_unit::exec():
    - cleanup
    - call set_limit explicitly as it has been moved out of 
     init_prepare_fake_select_lex.
sql/sql_update.cc:
  - setup_tables signature changed

1 files changed, 9 insertions, 12 deletions

diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index 0fbcf32a83c..8e5ae7c6a42 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -537,8 +537,6 @@ Item_exists_subselect::Item_exists_subselect(st_select_lex *select_lex):
   null_value= 0; //can't be NULL
   maybe_null= 0; //can't be NULL
   value= 0;
-  // We need only 1 row to determinate existence
-  select_lex->master_unit()->global_parameters->select_limit= 1;
   DBUG_VOID_RETURN;
 }
 
@@ -605,6 +603,8 @@ void Item_exists_subselect::fix_length_and_dec()
    decimals= 0;
    max_length= 1;
    max_columns= engine->cols();
+   /* We need only 1 row to determinate existence */
+  unit->global_parameters->select_limit= 1;
 }
 
 double Item_exists_subselect::val_real()
@@ -854,9 +854,6 @@ Item_in_subselect::single_value_transformer(JOIN *join,
     else
     {
       Item_maxmin_subselect *item;
-      // remove LIMIT placed  by ALL/ANY subquery
-      select_lex->master_unit()->global_parameters->select_limit=
-	HA_POS_ERROR;
       subs= item= new Item_maxmin_subselect(thd, this, select_lex, func->l_op());
       if (upper_item)
         upper_item->set_sub_test(item);
@@ -1286,13 +1283,10 @@ subselect_single_select_engine(st_select_lex *select,
 			       select_subselect *result,
 			       Item_subselect *item)
   :subselect_engine(item, result),
-   prepared(0), optimized(0), executed(0), join(0)
+   prepared(0), optimized(0), executed(0),
+   select_lex(select), join(0)
 {
-  select_lex= select;
-  SELECT_LEX_UNIT *unit= select_lex->master_unit();
-  unit->set_limit(unit->global_parameters, select_lex);
-  unit->item= item;
-  this->select_lex= select_lex;
+  select_lex->master_unit()->item= item;
 }
 
 
@@ -1440,7 +1434,10 @@ int subselect_single_select_engine::exec()
   thd->lex->current_select= select_lex;
   if (!optimized)
   {
-    optimized=1;
+    SELECT_LEX_UNIT *unit= select_lex->master_unit();
+
+    optimized= 1;
+    unit->set_limit(unit->global_parameters);
     if (join->optimize())
     {
       thd->where= save_where;