Merge olga.mysql.com:/home/igor/dev-opt/mysql-4.1-opt-bug28272

into  olga.mysql.com:/home/igor/dev-opt/mysql-5.0-opt-bug28272

mysql-test/r/innodb_mysql.result

@@ -144,6 +144,27 @@ SELECT * FROM t1;
 c1	cnt
 1a	2
 DROP TABLE t1;
+CREATE TABLE t1 (
+a1 decimal(10,0) DEFAULT NULL,
+a2 blob,
+a3 time DEFAULT NULL,
+a4 blob,
+a5 char(175) DEFAULT NULL,
+a6 timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
+a7 tinyblob,
+INDEX idx (a6,a7(239),a5)
+) ENGINE=InnoDB;
+EXPLAIN SELECT a4 FROM t1 WHERE
+a6=NULL AND
+a4='UNcT5pIde4I6c2SheTo4gt92OV1jgJCVkXmzyf325R1DwLURkbYHwhydANIZMbKTgdcR5xS';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+EXPLAIN SELECT t1.a4 FROM t1, t1 t WHERE
+t.a6=t.a6 AND t1.a6=NULL AND
+t1.a4='UNcT5pIde4I6c2SheTo4gt92OV1jgJCVkXmzyf325R1DwLURkbYHwhydANIZMbKTgdcR5xS';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+DROP TABLE t1;
 End of 4.1 tests
 create table t1m (a int) engine=myisam;
 create table t1i (a int) engine=innodb;

mysql-test/t/innodb_mysql.test

@@ -169,6 +169,31 @@ INSERT INTO t1 (c1) VALUES ('1b') ON DUPLICATE KEY UPDATE cnt=cnt+1;
 SELECT * FROM t1;
 DROP TABLE t1;
 
+#
+# Bug #28272: EXPLAIN for SELECT from an empty InnoDB table
+#
+
+CREATE TABLE t1 (
+  a1 decimal(10,0) DEFAULT NULL,
+  a2 blob,
+  a3 time DEFAULT NULL,
+  a4 blob,
+  a5 char(175) DEFAULT NULL,
+  a6 timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
+  a7 tinyblob,
+  INDEX idx (a6,a7(239),a5)
+) ENGINE=InnoDB;
+
+EXPLAIN SELECT a4 FROM t1 WHERE
+a6=NULL AND
+a4='UNcT5pIde4I6c2SheTo4gt92OV1jgJCVkXmzyf325R1DwLURkbYHwhydANIZMbKTgdcR5xS';
+
+EXPLAIN SELECT t1.a4 FROM t1, t1 t WHERE
+t.a6=t.a6 AND t1.a6=NULL AND
+t1.a4='UNcT5pIde4I6c2SheTo4gt92OV1jgJCVkXmzyf325R1DwLURkbYHwhydANIZMbKTgdcR5xS';
+
+DROP TABLE t1;
+
 --echo End of 4.1 tests
 #
 # Bug #12882  	min/max inconsistent on empty table

sql/sql_select.cc

@@ -976,6 +976,12 @@ JOIN::optimize()
     }
   }
 
+  if (conds &&!outer_join && const_table_map != found_const_table_map && 
+      (select_options & SELECT_DESCRIBE) &&
+      select_lex->master_unit() == &thd->lex->unit) // upper level SELECT
+  {
+    conds=new Item_int((longlong) 0,1);	// Always false
+  }
   if (make_join_select(this, select, conds))
   {
     zero_result_cause=