MDEV-23983: Crash caused by query containing constant having clause

Before this patch the crash occured when a single row dataset is used and
Item::remove_eq_conds() is called for HAVING. This function is not supposed
to be called after the elimination of multiple equalities.

To fix this problem instead of Item::remove_eq_conds() Item::val_int() is
used. In this case the optimizer tries to evaluate the condition for the
single row dataset and discovers impossible HAVING immediately. So, the
execution phase is skipped.

Approved by Igor Babaev <igor@maridb.com>

mysql-test/main/having.result

@@ -955,3 +955,47 @@ DROP TABLE t;
 #
 # End of 10.4 tests
 #
+#
+# MDEV-23983: Crash caused by query containing constant having clause
+#
+CREATE TABLE t1 (id INT PRIMARY KEY, a INT, b TEXT, c INT);
+INSERT INTO t1 VALUES (3, 7, 'b', 1), (4, 7, 'b', 1);
+SELECT * FROM t1
+WHERE t1.id = 3
+GROUP BY t1.a
+HAVING t1.b = 'b' and t1.c = 1;
+id	a	b	c
+3	7	b	1
+SELECT * FROM t1
+WHERE t1.id = 3
+GROUP BY t1.a
+HAVING t1.b = 'b' and t1.c = 2;
+id	a	b	c
+explain SELECT * FROM t1
+WHERE t1.id = 3
+GROUP BY t1.a
+HAVING t1.b = 'b' and t1.c = 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible HAVING noticed after reading const tables
+DROP TABLE t1;
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+CREATE TABLE t2 (id INT, b TEXT, c INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (3, 'b', 1);
+SELECT t2.* FROM t2 LEFT JOIN t1 ON t2.id = t1.a
+GROUP BY t2.id
+HAVING t2.b = 'b' and t2.c = 1;
+id	b	c
+3	b	1
+SELECT t2.* FROM t2 LEFT JOIN t1 ON t2.id = t1.a
+GROUP BY t2.id
+HAVING t2.b = 'b' and t2.c = 2;
+id	b	c
+explain SELECT t2.* FROM t2 LEFT JOIN t1 ON t2.id = t1.a
+GROUP BY t2.id
+HAVING t2.b = 'b' and t2.c = 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible HAVING noticed after reading const tables
+DROP TABLE t1,t2;
+#
+# End of 10.5 tests
+#

mysql-test/main/having.test

@@ -1011,3 +1011,48 @@ DROP TABLE t;
 --echo #
 --echo # End of 10.4 tests
 --echo #
+
+--echo #
+--echo # MDEV-23983: Crash caused by query containing constant having clause
+--echo #
+
+CREATE TABLE t1 (id INT PRIMARY KEY, a INT, b TEXT, c INT);
+INSERT INTO t1 VALUES (3, 7, 'b', 1), (4, 7, 'b', 1);
+
+SELECT * FROM t1
+WHERE t1.id = 3
+GROUP BY t1.a
+HAVING t1.b = 'b' and t1.c = 1;
+
+let $q=
+SELECT * FROM t1
+WHERE t1.id = 3
+GROUP BY t1.a
+HAVING t1.b = 'b' and t1.c = 2;
+
+eval $q;
+eval explain $q;
+
+DROP TABLE t1;
+
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+CREATE TABLE t2 (id INT, b TEXT, c INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (3, 'b', 1);
+
+SELECT t2.* FROM t2 LEFT JOIN t1 ON t2.id = t1.a
+GROUP BY t2.id
+HAVING t2.b = 'b' and t2.c = 1;
+
+let $q=
+SELECT t2.* FROM t2 LEFT JOIN t1 ON t2.id = t1.a
+GROUP BY t2.id
+HAVING t2.b = 'b' and t2.c = 2;
+
+eval $q;
+eval explain $q;
+
+DROP TABLE t1,t2;
+
+--echo #
+--echo # End of 10.5 tests
+--echo #

sql/sql_select.cc

@@ -2971,19 +2971,22 @@ int JOIN::optimize_stage2()
     which do not use aggregate functions. In such case
     temporary table may not be used and const condition
     elements may be lost during further having
-    condition transformation in JOIN::exec.
+    condition transformation.
   */
   if (having && const_table_map && !having->with_sum_func())
   {
     having->update_used_tables();
-    having= having->remove_eq_conds(thd, &select_lex->having_value, true);
-    if (select_lex->having_value == Item::COND_FALSE)
+    if (having->const_item() && !having->is_expensive())
     {
-      having= new (thd->mem_root) Item_bool(thd, false);
-      zero_result_cause= "Impossible HAVING noticed after reading const tables";
-      error= 0;
-      select_lex->mark_const_derived(zero_result_cause);
-      goto setup_subq_exit;
+      bool having_value= having->val_int();
+      having= new (thd->mem_root) Item_bool(thd, having_value);
+      if (!having_value)
+      {
+        zero_result_cause= "Impossible HAVING noticed after reading const tables";
+        error= 0;
+        select_lex->mark_const_derived(zero_result_cause);
+        goto setup_subq_exit;
+      }
     }
   }