MDEV-28858 Wrong result with table elimination combined with not_null…

…_range_scan

The bug was that build_notnull_conds_for_range_scans() did not take into
account the join_tab is not yet sorted with constant tables first.
Fixed the bug by testing explicitely if a table is a const table.

mysql-test/main/range.result

@@ -3635,6 +3635,25 @@ SELECT * FROM t1 LEFT JOIN t2 ON a = pk WHERE b >= 0 AND pk IS NULL;
 a	pk	b
 DROP TABLE t1, t2;
 SET @@optimizer_switch= @save_optimizer_switch;
+
+# MDEV-28858 Wrong result with table elimination combined with
+# not_null_range_scan
+#
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES  (10,1),(null,2);
+CREATE TABLE t2 (pk INT PRIMARY KEY) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(2);
+SET @save_optimizer_switch= @@optimizer_switch;
+SET optimizer_switch= 'not_null_range_scan=on';
+SELECT t1.b FROM t1 LEFT JOIN t2 ON t1.a = t2.pk WHERE t1.a IS NULL ORDER BY t1.b;
+b
+2
+SET optimizer_switch= 'not_null_range_scan=off';
+SELECT t1.b FROM t1 LEFT JOIN t2 ON t1.a = t2.pk WHERE t1.a IS NULL ORDER BY t1.b;
+b
+2
+SET @@optimizer_switch=@save_optimizer_switch;
+drop table t1,t2;
 #
 # End of 10.5 tests
 #

mysql-test/main/range.test

@@ -2492,6 +2492,24 @@ DROP TABLE t1, t2;
 
 SET @@optimizer_switch= @save_optimizer_switch;
 
+--echo
+--echo # MDEV-28858 Wrong result with table elimination combined with
+--echo # not_null_range_scan
+--echo #
+
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES  (10,1),(null,2);
+CREATE TABLE t2 (pk INT PRIMARY KEY) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(2);
+
+SET @save_optimizer_switch= @@optimizer_switch;
+SET optimizer_switch= 'not_null_range_scan=on';
+SELECT t1.b FROM t1 LEFT JOIN t2 ON t1.a = t2.pk WHERE t1.a IS NULL ORDER BY t1.b;
+SET optimizer_switch= 'not_null_range_scan=off';
+SELECT t1.b FROM t1 LEFT JOIN t2 ON t1.a = t2.pk WHERE t1.a IS NULL ORDER BY t1.b;
+SET @@optimizer_switch=@save_optimizer_switch;
+drop table t1,t2;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #

mysql-test/main/range_mrr_icp.result

@@ -3624,6 +3624,25 @@ SELECT * FROM t1 LEFT JOIN t2 ON a = pk WHERE b >= 0 AND pk IS NULL;
 a	pk	b
 DROP TABLE t1, t2;
 SET @@optimizer_switch= @save_optimizer_switch;
+
+# MDEV-28858 Wrong result with table elimination combined with
+# not_null_range_scan
+#
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES  (10,1),(null,2);
+CREATE TABLE t2 (pk INT PRIMARY KEY) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(2);
+SET @save_optimizer_switch= @@optimizer_switch;
+SET optimizer_switch= 'not_null_range_scan=on';
+SELECT t1.b FROM t1 LEFT JOIN t2 ON t1.a = t2.pk WHERE t1.a IS NULL ORDER BY t1.b;
+b
+2
+SET optimizer_switch= 'not_null_range_scan=off';
+SELECT t1.b FROM t1 LEFT JOIN t2 ON t1.a = t2.pk WHERE t1.a IS NULL ORDER BY t1.b;
+b
+2
+SET @@optimizer_switch=@save_optimizer_switch;
+drop table t1,t2;
 #
 # End of 10.5 tests
 #

sql/sql_select.cc

@@ -29573,11 +29573,12 @@ bool build_notnull_conds_for_range_scans(JOIN *join, Item *cond,
 
   DBUG_ENTER("build_notnull_conds_for_range_scans");
 
-  for (JOIN_TAB *s= join->join_tab + join->const_tables ;
+  for (JOIN_TAB *s= join->join_tab;
        s < join->join_tab + join->table_count ; s++)
   {
     /* Clear all needed bitmaps to mark found fields */
-    if (allowed & s->table->map)
+    if ((allowed & s->table->map) &&
+        !(s->table->map && join->const_table_map))
       bitmap_clear_all(&s->table->tmp_set);
   }
 
@@ -29592,17 +29593,18 @@ bool build_notnull_conds_for_range_scans(JOIN *join, Item *cond,
     For each table t from 'allowed' build a conjunction of NOT NULL predicates
     constructed for all found fields if they are included in some indexes.
     If the construction of the conjunction succeeds attach the formula to
-    t->table->notnull_cond. The condition will be used to look for complementary
-    range scans.
+    t->table->notnull_cond. The condition will be used to look for
+    complementary range scans.
   */
-  for (JOIN_TAB *s= join->join_tab + join->const_tables ;
+  for (JOIN_TAB *s= join->join_tab ;
        s < join->join_tab + join->table_count ; s++)
   {
     TABLE *tab= s->table;
     List<Item> notnull_list;
     Item *notnull_cond= 0;
 
-    if (!(allowed & tab->map))
+    if (!(allowed & tab->map) ||
+        (s->table->map && join->const_table_map))
       continue;
 
     for (Field** field_ptr= tab->field; *field_ptr; field_ptr++)