Fixed bug #30396.

The bug caused memory corruption for some queries with top OR level
in the WHERE condition if they contained equality predicates and 
other sargable predicates in disjunctive parts of the condition.

The corruption happened because the upper bound of the memory
allocated for KEY_FIELD and SARGABLE_PARAM internal structures
containing info about potential lookup keys was calculated incorrectly
in some cases. In particular it was calculated incorrectly when the
WHERE condition was an OR formula with disjuncts being AND formulas
including equalities and other sargable predicates.


mysql-test/r/select.result:
  Added a test case for bug #30396.
mysql-test/t/select.test:
  Added a test case for bug #30396.
sql/item_cmpfunc.h:
  Removed max_members from the COND_EQUAL class as not useful anymore.
sql/sql_base.cc:
  Added the max_equal_elems field to the st_select_lex structure.
sql/sql_lex.cc:
  Added the max_equal_elems field to the st_select_lex structure.
sql/sql_lex.h:
  Added the max_equal_elems field to the st_select_lex structure.
  The field contains the maximal number of elements in multiple equalities
  built for the query conditions.
sql/sql_select.cc:
  Fixed bug #30396.
  The bug caused memory corruption for some queries with top OR level
  in the WHERE condition if they contained equality predicates and 
  other sargable predicates in disjunctive parts of the condition.
  
  The corruption happened because the upper bound of the memory
  allocated for KEY_FIELD and SARGABLE_PARAM internal structures
  containing info about potential lookup keys was calculated incorrectly
  in some cases. In particular it was calculated incorrectly when the
  WHERE condition was an OR formula with disjuncts being AND formulas
  including equalities and other sargable predicates.
   
  The max_equal_elems field to the st_select_lex structure is used now
  to calculate the above mentioned upper bound. The field contains the
  maximal number of elements in multiple equalities built for the query
  conditions.

5 files changed, 16 insertions, 28 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 9afc0507817..7b6eaef08ec 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -1506,7 +1506,6 @@ public:
                                      the current and level           */
   COND_EQUAL()
   { 
-    max_members= 0;
     upper_levels= 0;
   }
 };
diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 1c01248c283..e8562cdffbd 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -5611,6 +5611,7 @@ int setup_conds(THD *thd, TABLE_LIST *tables, TABLE_LIST *leaves,
   thd->set_query_id=1;
   select_lex->cond_count= 0;
   select_lex->between_count= 0;
+  select_lex->max_equal_elems= 0;
 
   for (table= tables; table; table= table->next_local)
   {
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 7911da69862..d11c2b21635 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -1183,6 +1183,7 @@ void st_select_lex::init_query()
   */
   parent_lex->push_context(&context);
   cond_count= between_count= with_wild= 0;
+  max_equal_elems= 0;
   conds_processed_with_permanent_arena= 0;
   ref_pointer_array= 0;
   select_n_where_fields= 0;
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index b9c6abd2b06..94015a9fe07 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -533,7 +533,8 @@ public:
   */
   uint select_n_having_items;
   uint cond_count;    /* number of arguments of and/or/xor in where/having/on */
-  uint between_count; /* number of between predicates in where/having/on      */   
+  uint between_count; /* number of between predicates in where/having/on      */
+  uint max_equal_elems; /* maximal number of elements in multiple equalities  */   
   /*
     Number of fields used in select list or where clause of current select
     and all inner subselects.
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index ac8dc84f118..b7846a7433d 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -3524,10 +3524,7 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
   uint	and_level,i,found_eq_constant;
   KEY_FIELD *key_fields, *end, *field;
   uint sz;
-  uint m= 1;
-  
-  if (cond_equal && cond_equal->max_members)
-    m= cond_equal->max_members;
+  uint m= max(select_lex->max_equal_elems,1);
   
   /* 
     We use the same piece of memory to store both  KEY_FIELD 
@@ -3547,7 +3544,8 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
     it is considered as sargable only for its first argument.
     Multiple equality can add  elements that are filled after
     substitution of field arguments by equal fields. There
-    can be not more than cond_equal->max_members such substitutions.
+    can be not more than select_lex->max_equal_elems such 
+    substitutions.
   */ 
   sz= max(sizeof(KEY_FIELD),sizeof(SARGABLE_PARAM))*
       (((thd->lex->current_select->cond_count+1)*2 +
@@ -7189,8 +7187,7 @@ static bool check_equality(THD *thd, Item *item, COND_EQUAL *cond_equal,
     just an argument of a comparison predicate.
     The function also determines the maximum number of members in 
     equality lists of each Item_cond_and object assigning it to
-    cond_equal->max_members of this object and updating accordingly
-    the upper levels COND_EQUAL structures.  
+    thd->lex->current_select->max_equal_elems.
 
   NOTES
     Multiple equality predicate =(f1,..fn) is equivalent to the conjuction of
@@ -7235,7 +7232,6 @@ static COND *build_equal_items_for_cond(THD *thd, COND *cond,
                                         COND_EQUAL *inherited)
 {
   Item_equal *item_equal;
-  uint members;
   COND_EQUAL cond_equal;
   cond_equal.upper_levels= inherited;
 
@@ -7273,19 +7269,8 @@ static COND *build_equal_items_for_cond(THD *thd, COND *cond,
       {
         item_equal->fix_length_and_dec();
         item_equal->update_used_tables();
-        members= item_equal->members();
-        if (cond_equal.max_members < members)
-          cond_equal.max_members= members; 
-      }
-      members= cond_equal.max_members;
-      if (inherited && inherited->max_members < members)
-      {
-        do
-        {
-	  inherited->max_members= members;
-          inherited= inherited->upper_levels;
-        }
-        while (inherited);
+        set_if_bigger(thd->lex->current_select->max_equal_elems,
+                      item_equal->members());  
       }
 
       ((Item_cond_and*)cond)->cond_equal= cond_equal;
@@ -7340,10 +7325,12 @@ static COND *build_equal_items_for_cond(THD *thd, COND *cond,
         {
           item_equal->fix_length_and_dec();
           item_equal->update_used_tables();
-          return item_equal;
 	}
         else
-          return eq_list.pop();
+          item_equal= (Item_equal *) eq_list.pop();
+        set_if_bigger(thd->lex->current_select->max_equal_elems,
+                      item_equal->members());  
+        return item_equal;
       }
       else
       {
@@ -7359,9 +7346,8 @@ static COND *build_equal_items_for_cond(THD *thd, COND *cond,
         {
           item_equal->fix_length_and_dec();
           item_equal->update_used_tables();
-          members= item_equal->members();
-          if (cond_equal.max_members < members)
-            cond_equal.max_members= members; 
+          set_if_bigger(thd->lex->current_select->max_equal_elems,
+                        item_equal->members());  
         }
         and_cond->cond_equal= cond_equal;
         args->concat((List<Item> *)&cond_equal.current_level);