BUG#997747: Assertion `join->best_read < ((double)1.79..5e+308L)' failed

  in greedy_search with LEFT JOINs and unique keys
- Backport the fix for BUG#806524 from MariaDB 5.3

mysql-test/r/table_elim.result

@@ -566,3 +566,24 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 # ^^ The above must not produce a QEP of t3,t5,t2,t4
 #    as that violates the "no interleaving of outer join nests" rule.
 DROP TABLE t1,t2,t3,t4,t5;
+#
+# BUG#997747: Assertion `join->best_read < ((double)1.79..5e+308L)' 
+#             failed in greedy_search with LEFT JOINs and unique keys  
+#
+CREATE TABLE t1 (a1 INT);
+CREATE TABLE t2 (b1 INT);
+CREATE TABLE t3 (c1 INT, UNIQUE KEY(c1));
+CREATE TABLE t4 (d1 INT, UNIQUE KEY(d1));
+CREATE TABLE t5 (e1 INT);
+INSERT INTO t1 VALUES (1),(2);
+INSERT INTO t2 VALUES (2),(3);
+INSERT INTO t3 VALUES (3),(4);
+INSERT INTO t4 VALUES (4),(5);
+INSERT INTO t5 VALUES (5),(6);
+SELECT a1 FROM t1 LEFT JOIN t2 LEFT JOIN t3 LEFT JOIN t4
+ON c1 = d1 ON d1 = b1 ON a1 = b1
+LEFT JOIN t5 ON a1 = e1 ;
+a1
+1
+2
+DROP TABLE t1,t2,t3,t4,t5;

mysql-test/t/table_elim.test

@@ -499,3 +499,25 @@ WHERE t3.f2 ;
 
 DROP TABLE t1,t2,t3,t4,t5;
 
+--echo #
+--echo # BUG#997747: Assertion `join->best_read < ((double)1.79..5e+308L)' 
+--echo #             failed in greedy_search with LEFT JOINs and unique keys  
+--echo #
+CREATE TABLE t1 (a1 INT);
+CREATE TABLE t2 (b1 INT);
+CREATE TABLE t3 (c1 INT, UNIQUE KEY(c1));
+CREATE TABLE t4 (d1 INT, UNIQUE KEY(d1));
+CREATE TABLE t5 (e1 INT);
+
+INSERT INTO t1 VALUES (1),(2);
+INSERT INTO t2 VALUES (2),(3);
+INSERT INTO t3 VALUES (3),(4);
+INSERT INTO t4 VALUES (4),(5);
+INSERT INTO t5 VALUES (5),(6);
+
+SELECT a1 FROM t1 LEFT JOIN t2 LEFT JOIN t3 LEFT JOIN t4
+ON c1 = d1 ON d1 = b1 ON a1 = b1
+LEFT JOIN t5 ON a1 = e1 ;
+
+DROP TABLE t1,t2,t3,t4,t5;
+

sql/sql_select.cc

@@ -9130,14 +9130,16 @@ static uint reset_nj_counters(JOIN *join, List<TABLE_LIST> *join_list)
   while ((table= li++))
   {
     NESTED_JOIN *nested_join;
+    bool is_eliminated_nest= FALSE;
     if ((nested_join= table->nested_join))
     {
       nested_join->counter= 0;
-      //nested_join->n_tables= my_count_bits(nested_join->used_tables & 
-      //                                     ~join->eliminated_tables);
       nested_join->n_tables= reset_nj_counters(join, &nested_join->join_list);
+      if (!nested_join->n_tables)
+        is_eliminated_nest= TRUE;
     }
-    if (!table->table || (table->table->map & ~join->eliminated_tables))
+    if ((table->nested_join && !is_eliminated_nest) || 
+        (!table->nested_join && (table->table->map & ~join->eliminated_tables)))
       n++;
   }
   DBUG_RETURN(n);