MDEV-31361 WIP: proof-of-concept

mysql-test/suite/federated/federatedx_create_handlers.result

@@ -514,6 +514,54 @@ WHERE id=2) dt2) dt
 a	b	a	b	id	name
 1	1	NULL	NULL	NULL	NULL
 2	2	NULL	NULL	NULL	NULL
+#
+# MDEV-31361: Wrong result on second execution of prepared statement
+#             for engine Federated with derived table
+#
+connection slave;
+DROP TABLE IF EXISTS federated.t1;
+CREATE TABLE federated.t1 (
+id int(20) NOT NULL,
+name varchar(16) NOT NULL default ''
+)
+DEFAULT CHARSET=latin1;
+INSERT INTO federated.t1 VALUES
+(3,'xxx'), (7,'yyy'), (4,'xxx'), (1,'zzz'), (5,'yyy');
+connection master;
+DROP TABLE IF EXISTS federated.t1;
+CREATE TABLE federated.t1 (
+id int(20) NOT NULL,
+name varchar(16) NOT NULL default ''
+)
+ENGINE="FEDERATED" DEFAULT CHARSET=latin1
+CONNECTION='mysql://root@127.0.0.1:SLAVE_PORT/federated/t1';
+use federated;
+SELECT * FROM
+(SELECT * FROM
+(SELECT * FROM
+(SELECT * FROM t1 where id>3) dt3
+WHERE id>3) dt2
+) dt;
+id	name
+7	yyy
+4	xxx
+5	yyy
+PREPARE stmt FROM 'SELECT * FROM
+  (SELECT * FROM
+    (SELECT * FROM
+        (SELECT * FROM t1 where id>3) dt3
+      WHERE id>3) dt2
+  ) dt';
+EXECUTE stmt;
+id	name
+7	yyy
+4	xxx
+5	yyy
+EXECUTE stmt;
+id	name
+7	yyy
+4	xxx
+5	yyy
 set global federated_pushdown=0;
 connection master;
 DROP TABLE IF EXISTS federated.t1;

mysql-test/suite/federated/federatedx_create_handlers.test

@@ -94,12 +94,9 @@ DEFAULT CHARSET=latin1;
 INSERT INTO federated.t3 VALUES
   ('yyy'), ('www'), ('yyy'), ('xxx'), ('www'), ('yyy'), ('www');
 
-#Enable after fix MDEV-31361
---disable_ps2_protocol
 SELECT *
 FROM federated.t3, (SELECT * FROM federated.t1 WHERE id > 3) t
 WHERE federated.t3.name=t.name;
---enable_ps2_protocol
 
 EXPLAIN
 SELECT *
@@ -376,6 +373,54 @@ SELECT * FROM t10 LEFT JOIN
     WHERE id=2) dt2) dt
   ) ON t10.a=t11.a;
 
+--echo #
+--echo # MDEV-31361: Wrong result on second execution of prepared statement
+--echo #             for engine Federated with derived table
+--echo #
+
+connection slave;
+DROP TABLE IF EXISTS federated.t1;
+
+CREATE TABLE federated.t1 (
+  id int(20) NOT NULL,
+  name varchar(16) NOT NULL default ''
+)
+DEFAULT CHARSET=latin1;
+
+INSERT INTO federated.t1 VALUES
+  (3,'xxx'), (7,'yyy'), (4,'xxx'), (1,'zzz'), (5,'yyy');
+
+connection master;
+DROP TABLE IF EXISTS federated.t1;
+
+--replace_result $SLAVE_MYPORT SLAVE_PORT
+eval
+CREATE TABLE federated.t1 (
+  id int(20) NOT NULL,
+  name varchar(16) NOT NULL default ''
+)
+ENGINE="FEDERATED" DEFAULT CHARSET=latin1
+CONNECTION='mysql://root@127.0.0.1:$SLAVE_MYPORT/federated/t1';
+
+use federated;
+SELECT * FROM
+  (SELECT * FROM
+    (SELECT * FROM
+        (SELECT * FROM t1 where id>3) dt3
+      WHERE id>3) dt2
+  ) dt;
+
+PREPARE stmt FROM 'SELECT * FROM
+  (SELECT * FROM
+    (SELECT * FROM
+        (SELECT * FROM t1 where id>3) dt3
+      WHERE id>3) dt2
+  ) dt';
+
+EXECUTE stmt;
+EXECUTE stmt;
+
+
 set global federated_pushdown=0;
 
 source include/federated_cleanup.inc;

sql/sql_derived.cc

@@ -351,13 +351,6 @@ bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived)
     DBUG_RETURN(FALSE);
   }
 
-  if (derived->dt_handler)
-  {
-    derived->change_refs_to_fields();
-    derived->set_materialized_derived();
-    DBUG_RETURN(FALSE);
-  }
-
   arena= thd->activate_stmt_arena_if_needed(&backup);  // For easier test
 
   if (!derived->merged_for_insert || 
@@ -379,6 +372,12 @@ bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived)
       goto unconditional_materialization;
     }
 
+    if (derived->is_pushed_down())
+    {
+      cause= "Pushed down derived tables must always be materialized";
+      goto unconditional_materialization;
+    }
+
     if (dt_select->options & OPTION_SCHEMA_TABLE)
       parent_lex->options |= OPTION_SCHEMA_TABLE;
 
@@ -869,6 +868,12 @@ bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived)
   if (derived->is_derived() && derived->is_merged_derived())
     first_select->mark_as_belong_to_derived(derived);
 
+  /*
+    Choosing an external executor of a derived table (also called the
+    "pushdown handler") must be the last step in mysql_derived_prepare,
+    because the external engine requires the preparation of the DT to be
+    fully completed.
+  */
   derived->dt_handler= derived->find_derived_handler(thd);
   if (derived->dt_handler)
   {

sql/sql_lex.cc

@@ -4922,7 +4922,7 @@ void st_select_lex::set_explain_type(bool on_the_fly)
       if (linkage == DERIVED_TABLE_TYPE)
       {
         bool is_pushed_master_unit= master_unit()->derived &&
-	                            master_unit()->derived->pushdown_derived;
+                                    master_unit()->derived->is_pushed_down();
         if (is_pushed_master_unit)
           type= pushed_derived_text;
         else if (is_uncacheable & UNCACHEABLE_DEPENDENT)

sql/table.h

@@ -2894,6 +2894,11 @@ struct TABLE_LIST
   {
     derived_type|= DTYPE_MULTITABLE;
   }
+  bool is_pushed_down() const
+  {
+    return dt_handler != NULL;
+  }
+
   bool set_as_with_table(THD *thd, With_element *with_elem);
   void reset_const_table();
   bool handle_derived(LEX *lex, uint phases);