BUG#14553: NULL in WHERE resets LAST_INSERT_ID

To make MySQL compatible with some ODBC applications, you can find
the AUTO_INCREMENT value for the last inserted row with the following query:
 SELECT * FROM tbl_name WHERE auto_col IS NULL.
This is done with a special code that replaces 'auto_col IS NULL' with
'auto_col = LAST_INSERT_ID'.
However this also resets the LAST_INSERT_ID to 0 as it uses it for a flag
so as to ensure that only the first SELECT ... WHERE auto_col IS NULL
after an INSERT has this special behaviour.
In order to avoid resetting the LAST_INSERT_ID a special flag is introduced
in the THD class. This flag is used to restrict the second and subsequent
SELECTs instead of LAST_INSERT_ID.

mysql-test/r/odbc.result

@@ -14,3 +14,14 @@ explain select * from t1 where b is null;
 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;
+CREATE TABLE t1 (a INT AUTO_INCREMENT PRIMARY KEY);
+INSERT INTO t1 VALUES (NULL);
+SELECT sql_no_cache a, last_insert_id() FROM t1 WHERE a IS NULL;
+a	last_insert_id()
+1	1
+SELECT sql_no_cache a, last_insert_id() FROM t1 WHERE a IS NULL;
+a	last_insert_id()
+SELECT sql_no_cache a, last_insert_id() FROM t1;
+a	last_insert_id()
+1	1
+DROP TABLE t1;

mysql-test/r/rpl_insert_id.result

@@ -73,3 +73,17 @@ CREATE TABLE t1 ( a INT UNIQUE );
 SET FOREIGN_KEY_CHECKS=0;
 INSERT INTO t1 VALUES (1),(1);
 ERROR 23000: Duplicate entry '1' for key 1
+drop table t1;
+create table t1(a int auto_increment, key(a));
+create table t2(a int);
+insert into t1 (a) values (null);
+insert into t2 (a) select a from t1 where a is null;
+insert into t2 (a) select a from t1 where a is null;
+select * from t2;
+a
+1
+select * from t2;
+a
+1
+drop table t1;
+drop table t2;

mysql-test/t/odbc.test

@@ -21,4 +21,14 @@ select * from t1 where a is null;
 explain select * from t1 where b is null;
 drop table t1;
 
+#
+# Bug #14553: NULL in WHERE resets LAST_INSERT_ID
+#
+CREATE TABLE t1 (a INT AUTO_INCREMENT PRIMARY KEY);
+INSERT INTO t1 VALUES (NULL);
+SELECT sql_no_cache a, last_insert_id() FROM t1 WHERE a IS NULL;
+SELECT sql_no_cache a, last_insert_id() FROM t1 WHERE a IS NULL;
+SELECT sql_no_cache a, last_insert_id() FROM t1;
+DROP TABLE t1;
+
 # End of 4.1 tests

mysql-test/t/rpl_insert_id.test

@@ -74,4 +74,22 @@ SET FOREIGN_KEY_CHECKS=0;
 INSERT INTO t1 VALUES (1),(1);
 sync_slave_with_master;
  
+#
+# Bug#14553: NULL in WHERE resets LAST_INSERT_ID
+#
+connection master;
+drop table t1;
+create table t1(a int auto_increment, key(a));
+create table t2(a int);
+insert into t1 (a) values (null);
+insert into t2 (a) select a from t1 where a is null;
+insert into t2 (a) select a from t1 where a is null;
+select * from t2;
+sync_slave_with_master;
+connection slave;
+select * from t2;
+connection master;
+drop table t1;
+drop table t2;
+sync_slave_with_master;
 # End of 4.1 tests

sql/sql_class.cc

@@ -265,6 +265,7 @@ THD::THD()
     ulong tmp=sql_rnd_with_mutex();
     randominit(&rand, tmp + (ulong) &rand, tmp + (ulong) ::query_id);
   }
+  substitute_null_with_insert_id = FALSE;
 }
 
 

sql/sql_class.h

@@ -893,6 +893,8 @@ public:
   bool       last_cuted_field;
   bool	     no_errors, password, is_fatal_error;
   bool	     query_start_used,last_insert_id_used,insert_id_used,rand_used;
+  /* for IS NULL => = last_insert_id() fix in remove_eq_conds() */
+  bool       substitute_null_with_insert_id;
   bool	     time_zone_used;
   bool	     in_lock_tables;
   bool       query_error, bootstrap, cleanup_done;
@@ -988,6 +990,7 @@ public:
   {
     last_insert_id= id_arg;
     insert_id_used=1;
+    substitute_null_with_insert_id= TRUE;
   }
   inline ulonglong insert_id(void)
   {

sql/sql_select.cc

@@ -4719,7 +4719,7 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
       Field *field=((Item_field*) args[0])->field;
       if (field->flags & AUTO_INCREMENT_FLAG && !field->table->maybe_null &&
 	  (thd->options & OPTION_AUTO_IS_NULL) &&
-	  thd->insert_id())
+	  thd->insert_id() && thd->substitute_null_with_insert_id)
       {
 #ifdef HAVE_QUERY_CACHE
 	query_cache_abort(&thd->net);
@@ -4733,7 +4733,7 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
 	  cond=new_cond;
 	  cond->fix_fields(thd, 0, &cond);
 	}
-	thd->insert_id(0);		// Clear for next request
+	thd->substitute_null_with_insert_id= FALSE;   // Clear for next request
       }
       /* fix to replace 'NULL' dates with '0' (shreeve@uci.edu) */
       else if (((field->type() == FIELD_TYPE_DATE) ||