BUG#920713: Wrong result (missing rows) with firstmatch+BNL, IN subquery, ...

- Disable use of join cache when we're using FirstMatch strategy, and the join
  order is such that subquery's inner tables are interleaved with outer.  Join 
  buffering code is incapable of handling such join orders.

- The testcase requires use of @@debug_optimizer_prefer_join_prefix to hit the bug, 
  but I'm pushing it anyway (including the mention of the variable in .test file), 
  so that it can be found and enabled when/if we get something comparable in the 
  main tree.

mysql-test/r/subselect_sj.result

@@ -2509,4 +2509,31 @@ a	b	d
 8	4	2
 5	5	5
 DROP TABLE t1, t2;
+#
+# BUG#920713: Wrong result (missing rows) with firstmatch+BNL, IN subquery, ...
+#
+CREATE TABLE t1 ( a VARCHAR(1) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('e'),('w'),('a'),('h'),('x'),('k'),('g');
+CREATE TABLE t2 ( b INT, c VARCHAR(1) );
+INSERT INTO t2 VALUES (0,'j'),(8,'v');
+SELECT * FROM t1 alias1, t2 alias2
+WHERE alias2.c IN (
+SELECT alias4.c FROM t1 alias3, t2 alias4
+);
+a	b	c
+e	0	j
+e	8	v
+w	0	j
+w	8	v
+a	0	j
+a	8	v
+h	0	j
+h	8	v
+x	0	j
+x	8	v
+k	0	j
+k	8	v
+g	0	j
+g	8	v
+DROP TABLE t1, t2;
 set optimizer_switch=@subselect_sj_tmp;

mysql-test/r/subselect_sj_jcl6.result

@@ -2523,6 +2523,33 @@ a	b	d
 10	2	1
 10	2	1
 DROP TABLE t1, t2;
+#
+# BUG#920713: Wrong result (missing rows) with firstmatch+BNL, IN subquery, ...
+#
+CREATE TABLE t1 ( a VARCHAR(1) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('e'),('w'),('a'),('h'),('x'),('k'),('g');
+CREATE TABLE t2 ( b INT, c VARCHAR(1) );
+INSERT INTO t2 VALUES (0,'j'),(8,'v');
+SELECT * FROM t1 alias1, t2 alias2
+WHERE alias2.c IN (
+SELECT alias4.c FROM t1 alias3, t2 alias4
+);
+a	b	c
+e	0	j
+e	8	v
+w	0	j
+w	8	v
+a	0	j
+a	8	v
+h	0	j
+h	8	v
+x	0	j
+x	8	v
+k	0	j
+k	8	v
+g	0	j
+g	8	v
+DROP TABLE t1, t2;
 set optimizer_switch=@subselect_sj_tmp;
 #
 # BUG#49129: Wrong result with IN-subquery with join_cache_level=6 and firstmatch=off

mysql-test/t/subselect_sj.test

@@ -2252,6 +2252,23 @@ WHERE ( b, d ) IN
 
 DROP TABLE t1, t2;
 
+--echo #
+--echo # BUG#920713: Wrong result (missing rows) with firstmatch+BNL, IN subquery, ...
+--echo #
+# t1 should be MyISAM or InnoDB
+CREATE TABLE t1 ( a VARCHAR(1) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('e'),('w'),('a'),('h'),('x'),('k'),('g');
+CREATE TABLE t2 ( b INT, c VARCHAR(1) );
+INSERT INTO t2 VALUES (0,'j'),(8,'v');
+
+#SET debug_optimizer_prefer_join_prefix= 'alias2,alias4,alias1,alias3';
+
+SELECT * FROM t1 alias1, t2 alias2
+WHERE alias2.c IN (
+  SELECT alias4.c FROM t1 alias3, t2 alias4
+);
+
+DROP TABLE t1, t2;
 
 # The following command must be the last one the file 
 set optimizer_switch=@subselect_sj_tmp;

sql/opt_subselect.cc

@@ -4079,7 +4079,8 @@ int setup_semijoin_dups_elimination(JOIN *join, ulonglong options,
 {
   uint i;
   DBUG_ENTER("setup_semijoin_dups_elimination");
-
+  
+  join->complex_firstmatch_tables= table_map(0);
 
   POSITION *pos= join->best_positions + join->const_tables;
   for (i= join->const_tables ; i < join->top_join_tab_count; )
@@ -4165,8 +4166,13 @@ int setup_semijoin_dups_elimination(JOIN *join, ulonglong options,
       {
         JOIN_TAB *j;
         JOIN_TAB *jump_to= tab-1;
+
+        bool complex_range= FALSE;
+        table_map tables_in_range= table_map(0);
+
         for (j= tab; j != tab + pos->n_sj_tables; j++)
         {
+          tables_in_range |= j->table->map;
           if (!j->emb_sj_nest)
           {
             /* 
@@ -4176,11 +4182,12 @@ int setup_semijoin_dups_elimination(JOIN *join, ulonglong options,
               SELECT * FROM ot1, nt1 WHERE ot1.col IN (SELECT expr FROM it1, it2)
 
               with a join order of 
-                   
 
-              ot1 it1 nt1 nt2
+                   +----- FirstMatch range ----+
+                   |                           |
+              ot1 it1 nt1 nt2 it2 it3 ...
                    |   ^
-                   |   +-------- 'j' point here
+                   |   +-------- 'j' points here
                    +------------- SJ_OPT_FIRST_MATCH was set for this table as
                                   it's the first one that produces duplicates
               
@@ -4195,6 +4202,7 @@ int setup_semijoin_dups_elimination(JOIN *join, ulonglong options,
               j[-1].do_firstmatch= jump_to;
 
             jump_to= j; /* Jump back to us */
+            complex_range= TRUE;
           }
           else
           {
@@ -4205,6 +4213,9 @@ int setup_semijoin_dups_elimination(JOIN *join, ulonglong options,
         j[-1].do_firstmatch= jump_to;
         i+= pos->n_sj_tables;
         pos+= pos->n_sj_tables;
+
+        if (complex_range)
+          join->complex_firstmatch_tables|= tables_in_range;
         break;
       }
       case SJ_OPT_NONE:

sql/sql_select.cc

@@ -9153,6 +9153,9 @@ uint check_join_cache_usage(JOIN_TAB *tab,
 
   if (tab->use_quick == 2)
     goto no_join_cache;
+
+  if (tab->table->map & join->complex_firstmatch_tables)
+    goto no_join_cache;
   
   /*
     Don't use join cache if we're inside a join tab range covered by LooseScan
@@ -9363,7 +9366,7 @@ void check_join_cache_usage_for_tables(JOIN *join, ulonglong options,
   {
     tab->used_join_cache_level= join->max_allowed_join_cache_level;  
   }
-  
+
   uint idx= join->const_tables;
   for (tab= first_linear_tab(join, WITHOUT_CONST_TABLES); 
        tab; 
@@ -9448,6 +9451,8 @@ make_join_readinfo(JOIN *join, ulonglong options, uint no_jbuf_after)
   bool statistics= test(!(join->select_options & SELECT_DESCRIBE));
   bool sorted= 1;
 
+  join->complex_firstmatch_tables= table_map(0);
+
   if (!join->select_lex->sj_nests.is_empty() &&
       setup_semijoin_dups_elimination(join, options, no_jbuf_after))
     DBUG_RETURN(TRUE); /* purecov: inspected */

sql/sql_select.h

@@ -995,6 +995,13 @@ public:
   
   /* We also maintain a stack of join optimization states in * join->positions[] */
 /******* Join optimization state members end *******/
+
+  /*
+    Tables within complex firstmatch ranges (i.e. those where inner tables are
+    interleaved with outer tables). Join buffering cannot be used for these.
+  */
+  table_map complex_firstmatch_tables;
+
   /*
     The cost of best complete join plan found so far during optimization,
     after optimization phase - cost of picked join order (not taking into