A feature of doing automatick result buffering when INSERT is

done from the select containing a table to be inserted to.

mysql-test/r/insert.result

@@ -64,3 +64,16 @@ use test_$1;
 create table t1 (c int);
 insert into test_$1.t1 set test_$1.t1.c = '1';
 drop database test_$1;
+use test;
+drop table if exists t1,t2,t3;
+create table t1(id1 int not null auto_increment primary key, t char(12));
+create table t2(id2 int not null, t char(12));
+create table t3(id3 int not null, t char(12), index(id3));
+select count(*) from t2;
+count(*)
+500
+insert into  t2 select t1.* from t1, t2 t, t3 where  t1.id1 = t.id2 and t.id2 = t3.id3;
+select count(*) from t2;
+count(*)
+25500
+drop table if exists t1,t2,t3;

mysql-test/r/subselect.result

@@ -576,7 +576,6 @@ x
 3
 3
 INSERT INTO t1 (x) select (SELECT SUM(x)+2 FROM t1) FROM t2;
-You can't specify target table 't1' for update in FROM clause
 INSERT DELAYED INTO t1 (x) VALUES ((SELECT SUM(x) FROM t2));
 select * from t1;
 x
@@ -584,6 +583,8 @@ x
 2
 3
 3
+11
+11
 0
 drop table t1, t2, t3;
 CREATE TABLE t1 (x int not null, y int, primary key (x));

mysql-test/t/insert.test

@@ -65,3 +65,34 @@ use test_$1;
 create table t1 (c int);
 insert into test_$1.t1 set test_$1.t1.c = '1';
 drop database test_$1;
+use test;
+--disable_warnings
+drop table if exists t1,t2,t3;
+--enable_warnings
+create table t1(id1 int not null auto_increment primary key, t char(12));
+create table t2(id2 int not null, t char(12));
+create table t3(id3 int not null, t char(12), index(id3));
+disable_query_log;
+let $1 = 100;
+while ($1)
+ {
+  let $2 = 5;
+  eval insert into t1(t) values ('$1'); 
+  while ($2)
+   {
+     eval insert into t2(id2,t) values ($1,'$2'); 
+     let $3 = 10;
+     while ($3)
+     {
+       eval insert into t3(id3,t) values ($1,'$2'); 
+       dec $3;
+     }
+     dec $2; 
+   }
+  dec $1;
+ }
+enable_query_log;
+select count(*) from t2;
+insert into  t2 select t1.* from t1, t2 t, t3 where  t1.id1 = t.id2 and t.id2 = t3.id3;
+select count(*) from t2;
+drop table if exists t1,t2,t3;

mysql-test/t/subselect.test

@@ -332,7 +332,6 @@ INSERT DELAYED INTO t1 (x) VALUES ((SELECT SUM(a) FROM t2));
 select * from t1;
 INSERT INTO t1 (x) select (SELECT SUM(a)+1 FROM t2) FROM t2;
 select * from t1;
--- error 1093
 INSERT INTO t1 (x) select (SELECT SUM(x)+2 FROM t1) FROM t2;
 INSERT DELAYED INTO t1 (x) VALUES ((SELECT SUM(x) FROM t2));
 -- sleep 1

sql/sql_parse.cc

@@ -2198,8 +2198,7 @@ mysql_execute_command(THD *thd)
 
     if (find_real_table_in_list(tables->next, tables->db, tables->real_name))
     {
-      net_printf(thd,ER_UPDATE_TABLE_USED,tables->real_name);
-      return -1;
+      lex->select_lex.options |= OPTION_BUFFER_RESULT;    
     }
 
     /* Skip first table, which is the table we are inserting in */