MDEV-19580 Unrelated JOINs corrupt usage of 'WHERE function() IN (subquery)'

Handling of top level conjuncts in WHERE whose used_tables() contained
RAND_TABLE_BIT in the function make_join_select() was incorrect.
As a result if such a conjunct referred to fields non of which belonged
to the last joined table  it was pushed twice. (This could be seen
for a test case from subselect.test whose output was changed after this
patch had been applied. In 10.1 when running EXPLAIN FORMAT=JSON for
the query from this test case we clearly see that one of the conjuncts
is pushed twice.) This fact by itself was not good. Besides, if such a
conjunct was pushed to a table that was the result of materialization
of a semi-join the query could return a wrong result set. In particular
we could watch it for queries with semi-join subqueries whose left parts
used stored functions without "deterministic' specifier.

1 files changed, 73 insertions, 14 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 37f8292b563..d7ff92a5100 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -204,7 +204,8 @@ static COND *make_cond_for_table_from_pred(THD *thd, Item *root_cond,
                                            table_map used_table,
                                            int join_tab_idx_arg,
                                            bool exclude_expensive_cond,
-                                           bool retain_ref_cond);
+                                           bool retain_ref_cond,
+                                           bool is_top_and_level);
 
 static Item* part_of_refkey(TABLE *form,Field *field);
 uint find_shortest_key(TABLE *table, const key_map *usable_keys);
@@ -8922,12 +8923,6 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
                      RAND_TABLE_BIT;
       }
 
-      /*
-	Following force including random expression in last table condition.
-	It solve problem with select like SELECT * FROM t1 WHERE rand() > 0.5
-      */
-      if (tab == join->join_tab + last_top_base_tab_idx)
-        current_map|= RAND_TABLE_BIT;
       used_tables|=current_map;
 
       if (tab->type == JT_REF && tab->quick &&
@@ -8968,6 +8963,20 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
         {
           tmp= make_cond_for_table(thd, cond, used_tables, current_map, i,
                                    FALSE, FALSE);
+          if (tab == join->join_tab + last_top_base_tab_idx)
+          {
+            /*
+              This pushes conjunctive conditions of WHERE condition such that:
+              - their used_tables() contain RAND_TABLE_BIT
+              - the conditions does not refer to any fields
+              (such like rand() > 0.5)
+            */
+            table_map rand_table_bit= (table_map) RAND_TABLE_BIT;
+            COND *rand_cond= make_cond_for_table(thd, cond, used_tables,
+                                                 rand_table_bit, -1,
+                                                 FALSE, FALSE);
+            add_cond_and_fix(thd, &tmp, rand_cond);
+          }
         }
         /* Add conditions added by add_not_null_conds(). */
         if (tab->select_cond)
@@ -9283,8 +9292,24 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
             psergey: have put the -1 below. It's bad, will need to fix it.
           */
           COND *tmp_cond= make_cond_for_table(thd, on_expr, used_tables2,
-                                              current_map, /*(tab - first_tab)*/ -1,
-					      FALSE, FALSE);
+                                              current_map,
+                                              /*(tab - first_tab)*/ -1,
+                                              FALSE, FALSE);
+          if (tab == last_tab)
+          {
+            /*
+              This pushes conjunctive conditions of ON expression of an outer
+              join such that:
+              - their used_tables() contain RAND_TABLE_BIT
+              - the conditions does not refer to any fields
+              (such like rand() > 0.5)
+            */
+            table_map rand_table_bit= (table_map) RAND_TABLE_BIT;
+            COND *rand_cond= make_cond_for_table(thd, on_expr, used_tables2,
+                                                 rand_table_bit, -1,
+                                                 FALSE, FALSE);
+            add_cond_and_fix(thd, &tmp_cond, rand_cond);
+          }
           bool is_sjm_lookup_tab= FALSE;
           if (tab->bush_children)
           {
@@ -18824,7 +18849,7 @@ make_cond_for_table(THD *thd, Item *cond, table_map tables,
   return make_cond_for_table_from_pred(thd, cond, cond, tables, used_table,
                                        join_tab_idx_arg,
                                        exclude_expensive_cond,
-                                       retain_ref_cond);
+                                       retain_ref_cond, true);
 }
 
 
@@ -18834,9 +18859,12 @@ make_cond_for_table_from_pred(THD *thd, Item *root_cond, Item *cond,
                               int join_tab_idx_arg,
                               bool exclude_expensive_cond __attribute__
                               ((unused)),
-                              bool retain_ref_cond)
+                              bool retain_ref_cond,
+                              bool is_top_and_level)
 
 {
+  table_map rand_table_bit= (table_map) RAND_TABLE_BIT;
+
   if (used_table && !(cond->used_tables() & used_table))
     return (COND*) 0;				// Already checked
 
@@ -18852,11 +18880,28 @@ make_cond_for_table_from_pred(THD *thd, Item *root_cond, Item *cond,
       Item *item;
       while ((item=li++))
       {
+        /*
+          Special handling of top level conjuncts with RAND_TABLE_BIT:
+          if such a conjunct contains a reference to a field that is not
+          an outer field then it is pushed to the corresponding table by
+          the same rule as all other conjuncts. Otherwise, if the conjunct
+          is used in WHERE is is pushed to the last joined table, if is it
+          is used in ON condition of an outer join it is pushed into the
+          last inner table of the outer join. Such conjuncts are pushed in
+          a call of make_cond_for_table_from_pred() with the
+          parameter 'used_table' equal to PSEUDO_TABLE_BITS.
+        */
+        if (is_top_and_level && used_table == rand_table_bit &&
+            (item->used_tables() & ~OUTER_REF_TABLE_BIT) != rand_table_bit)
+        {
+          /* The conjunct with RAND_TABLE_BIT has been allready pushed */
+          continue;
+        }
 	Item *fix=make_cond_for_table_from_pred(thd, root_cond, item, 
                                                 tables, used_table,
-						join_tab_idx_arg,
+                                                join_tab_idx_arg,
                                                 exclude_expensive_cond,
-                                                retain_ref_cond);
+                                                retain_ref_cond, false);
 	if (fix)
 	  new_cond->argument_list()->push_back(fix);
       }
@@ -18880,6 +18925,13 @@ make_cond_for_table_from_pred(THD *thd, Item *root_cond, Item *cond,
     }
     else
     {						// Or list
+      if (is_top_and_level && used_table == rand_table_bit &&
+          (cond->used_tables() & ~OUTER_REF_TABLE_BIT) != rand_table_bit)
+      {
+        /* This top level formula with RAND_TABLE_BIT has been already pushed */
+        return (COND*) 0;
+      }
+
       Item_cond_or *new_cond=new Item_cond_or;
       if (!new_cond)
 	return (COND*) 0;			// OOM /* purecov: inspected */
@@ -18891,7 +18943,7 @@ make_cond_for_table_from_pred(THD *thd, Item *root_cond, Item *cond,
                                                 tables, 0L,
                                                 join_tab_idx_arg,
                                                 exclude_expensive_cond,
-                                                retain_ref_cond);
+                                                retain_ref_cond, false);
 	if (!fix)
 	  return (COND*) 0;			// Always true
 	new_cond->argument_list()->push_back(fix);
@@ -18908,6 +18960,13 @@ make_cond_for_table_from_pred(THD *thd, Item *root_cond, Item *cond,
     }
   }
 
+  if (is_top_and_level && used_table == rand_table_bit &&
+      (cond->used_tables() & ~OUTER_REF_TABLE_BIT) != rand_table_bit)
+  {
+    /* This top level formula with RAND_TABLE_BIT has been already pushed */
+    return (COND*) 0;
+  }
+
   /*
     Because the following test takes a while and it can be done
     table_count times, we mark each item that we have examined with the result