bk commit into 4.1 tree (gkodinov:1.2489) BUG#9676

[kgeorge]

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ChangeSet
  1.2489 06/06/15 18:26:50 gkodinov@stripped +3 -0
  * Bug #9676: INSERT INTO x SELECT .. FROM x LIMIT 1; slows down with big
                tables
  Currently in INSERT ... SELECT ... LIMIT ... the compiler uses a 
  temporary table to store the results of SELECT ... LIMIT .. and then
  uses that table as a source for INSERT. The problem is that in some cases
  it actually skips the LIMIT clause in doing that and materializes the 
  whole SELECT result set regardless of the LIMIT.
  This fix is limiting the process of filling up the temp table with only 
  that much rows that will be actually used by propagating the LIMIT value.

  sql/sql_select.cc
    1.456 06/06/15 18:26:45 gkodinov@stripped +8 -4
    * Bug #9676: INSERT INTO x SELECT .. FROM x LIMIT 1; slows down with big
                  tables
    - pass through the real LIMIT number if the temp table is created for
      buffering results.
    - set the counter for all the cases when the temp table is not used for
      grouping

  mysql-test/t/insert_select.test
    1.24 06/06/15 18:26:45 gkodinov@stripped +13 -0
    * Bug #9676: INSERT INTO x SELECT .. FROM x LIMIT 1; slows down with big
                  tables
    - a test demonstrating the code path

  mysql-test/r/insert_select.result
    1.30 06/06/15 18:26:45 gkodinov@stripped +4 -0
    * Bug #9676: INSERT INTO x SELECT .. FROM x LIMIT 1; slows down with big
                  tables
    - a test demonstrating the code path

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	gkodinov
# Host:	rakia.(none)
# Root:	/home/kgeorge/mysql/4.1/B9676

--- 1.455/sql/sql_select.cc	2006-06-03 00:14:52 +03:00
+++ 1.456/sql/sql_select.cc	2006-06-15 18:26:45 +03:00
@@ -888,8 +888,9 @@
 			   group_list ? 0 : select_distinct,
 			   group_list && simple_group,
 			   select_options,
-			   (order == 0 || skip_sort_order) ? select_limit :
-			   HA_POS_ERROR,
+			   (order == 0 || skip_sort_order || 
+                            test(select_options & OPTION_BUFFER_RESULT)) ? 
+                             select_limit : HA_POS_ERROR,
 			   (char *) "")))
       DBUG_RETURN(1);
 
@@ -5530,6 +5531,11 @@
       keyinfo->key_length+=  key_part_info->length;
     }
   }
+  else
+  {
+    set_if_smaller(table->max_rows, rows_limit);
+    param->end_write_records= rows_limit;
+  }
 
   if (distinct && field_count != param->hidden_field_count)
   {
@@ -5544,8 +5550,6 @@
     null_pack_length-=hidden_null_pack_length;
     keyinfo->key_parts= ((field_count-param->hidden_field_count)+
 			 test(null_pack_length));
-    set_if_smaller(table->max_rows, rows_limit);
-    param->end_write_records= rows_limit;
     table->distinct=1;
     table->keys=1;
     if (blob_count)

--- 1.29/mysql-test/r/insert_select.result	2005-10-25 19:02:11 +03:00
+++ 1.30/mysql-test/r/insert_select.result	2006-06-15 18:26:45 +03:00
@@ -686,3 +686,7 @@
 insert into t1(x,y) select x,z from t2 on duplicate key update x=values(t2.x);
 ERROR 42S02: Unknown table 't2' in field list
 drop table t1,t2;
+CREATE TABLE t1 (a int PRIMARY KEY);
+INSERT INTO t1 values (1), (2);
+INSERT INTO t1 SELECT a + 2 FROM t1 LIMIT 1;
+DROP TABLE t1;

--- 1.23/mysql-test/t/insert_select.test	2005-10-25 19:02:30 +03:00
+++ 1.24/mysql-test/t/insert_select.test	2006-06-15 18:26:45 +03:00
@@ -226,4 +226,17 @@
 insert into t1(x,y) select x,z from t2 on duplicate key update x=values(t2.x);
 drop table t1,t2; 
 
+#
+# Bug #9676: INSERT INTO x SELECT .. FROM x LIMIT 1; slows down with big 
+#             tables
+#
+
+#Note: not an exsaustive test : just a check of the code path.
+CREATE TABLE t1 (a int PRIMARY KEY);
+INSERT INTO t1 values (1), (2);
+
+INSERT INTO t1 SELECT a + 2 FROM t1 LIMIT 1;
+
+DROP TABLE t1;
+
 # End of 4.1 tests