BUG#6034 - Error code 124: Wrong medium type.

Version for 5.0. Committed for merge.
If the result table is one of the select tables in INSERT SELECT,
we must not disable the result tables indexes before selecting.
Now the preparation is split into two prepare methods.
The first detects the situation and defers some preparations
until the second phase.

mysql-test/r/insert_select.result

@@ -638,3 +638,15 @@ No	Field	Count
 0	1	100
 0	2	100
 drop table t1, t2;
+CREATE TABLE t1 (
+ID           int(11) NOT NULL auto_increment,
+NO           int(11) NOT NULL default '0',
+SEQ          int(11) NOT NULL default '0',
+PRIMARY KEY  (ID),
+KEY t1$NO    (SEQ,NO)
+) ENGINE=MyISAM;
+INSERT INTO t1 (SEQ, NO) SELECT "1" AS SEQ, IF(MAX(NO) IS NULL, 0, MAX(NO)) + 1 AS NO FROM t1 WHERE (SEQ = 1);
+select SQL_BUFFER_RESULT * from t1 WHERE (SEQ = 1);
+ID	NO	SEQ
+1	1	1
+drop table t1;

mysql-test/t/insert_select.test

@@ -180,3 +180,18 @@ insert into t2 Select null, Field, Count From t1 Where Month=20030901 and Type=2
 select * from t2;
 
 drop table t1, t2;
+
+#
+# BUG#6034 - Error code 124:  Wrong medium type
+#
+CREATE TABLE t1 (
+  ID           int(11) NOT NULL auto_increment,
+  NO           int(11) NOT NULL default '0',
+  SEQ          int(11) NOT NULL default '0',
+  PRIMARY KEY  (ID),
+  KEY t1$NO    (SEQ,NO)
+) ENGINE=MyISAM;
+INSERT INTO t1 (SEQ, NO) SELECT "1" AS SEQ, IF(MAX(NO) IS NULL, 0, MAX(NO)) + 1 AS NO FROM t1 WHERE (SEQ = 1);
+select SQL_BUFFER_RESULT * from t1 WHERE (SEQ = 1);
+drop table t1;
+

sql/sql_class.h

@@ -1280,6 +1280,7 @@ class select_result :public Sql_alloc {
     unit= u;
     return 0;
   }
+  virtual int prepare2(void) { return 0; }
   /*
     Because of peculiarities of prepared statements protocol
     we need to know number of columns in the result set (if
@@ -1379,6 +1380,7 @@ class select_insert :public select_result_interceptor {
 		enum_duplicates duplic, bool ignore);
   ~select_insert();
   int prepare(List<Item> &list, SELECT_LEX_UNIT *u);
+  int prepare2(void);
   bool send_data(List<Item> &items);
   virtual void store_values(List<Item> &values);
   void send_error(uint errcode,const char *err);

sql/sql_insert.cc

@@ -1802,13 +1802,22 @@ select_insert::prepare(List<Item> &values, SELECT_LEX_UNIT *u)
     thd->lex->current_select->options|= OPTION_BUFFER_RESULT;
     thd->lex->current_select->join->select_options|= OPTION_BUFFER_RESULT;
   }
-
+  else
+  {
+    /*
+      We must not yet prepare the result table if it is the same as one of the 
+      source tables (INSERT SELECT). The preparation may disable 
+      indexes on the result table, which may be used during the select, if it
+      is the same table (Bug #6034). Do the preparation after the select phase
+      in select_insert::prepare2().
+    */
+    if (info.ignore || info.handle_duplicates != DUP_ERROR)
+      table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
+    table->file->start_bulk_insert((ha_rows) 0);
+  }
   restore_record(table,s->default_values);		// Get empty record
   table->next_number_field=table->found_next_number_field;
   thd->cuted_fields=0;
-  if (info.ignore || info.handle_duplicates != DUP_ERROR)
-    table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
-  table->file->start_bulk_insert((ha_rows) 0);
   thd->no_trans_update= 0;
   thd->abort_on_warning= (!info.ignore &&
                           (thd->variables.sql_mode &
@@ -1819,6 +1828,36 @@ select_insert::prepare(List<Item> &values, SELECT_LEX_UNIT *u)
 }
 
 
+/*
+  Finish the preparation of the result table.
+
+  SYNOPSIS
+    select_insert::prepare2()
+    void
+
+  DESCRIPTION
+    If the result table is the same as one of the source tables (INSERT SELECT),
+    the result table is not finally prepared at the join prepair phase.
+    Do the final preparation now.
+		       
+  RETURN
+    0   OK
+*/
+
+int select_insert::prepare2(void)
+{
+  DBUG_ENTER("select_insert::prepare2");
+
+  if (thd->lex->current_select->options & OPTION_BUFFER_RESULT)
+  {
+    if (info.ignore || info.handle_duplicates != DUP_ERROR)
+      table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
+    table->file->start_bulk_insert((ha_rows) 0);
+  }
+  return 0;
+}
+
+
 void select_insert::cleanup()
 {
   /* select_insert/select_create are never re-used in prepared statement */

sql/sql_select.cc

@@ -1164,6 +1164,7 @@ JOIN::exec()
       DBUG_VOID_RETURN;
     }
   }
+  (void) result->prepare2(); // Currently, this cannot fail.
 
   if (!tables_list)
   {                                           // Only test of functions
@@ -13149,7 +13150,8 @@ bool JOIN::change_result(select_result *res)
 {
   DBUG_ENTER("JOIN::change_result");
   result= res;
-  if (!procedure && result->prepare(fields_list, select_lex->master_unit()))
+  if (!procedure && (result->prepare(fields_list, select_lex->master_unit()) ||
+                     result->prepare2()))
   {
     DBUG_RETURN(TRUE);
   }