bk commit into 4.1 tree (svoj:1.2534) BUG#21310

[Sergey Vojtovich]

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ChangeSet@stripped, 2006-11-23 19:50:37+04:00, svoj@stripped +3 -0
  BUG#21310 - Trees in SQL causing a "crashed" table with MyISAM storage engine
  
  An update that used a join of a table to itself and modified the
  table on one side of the join reported the table as crashed or
  updated wrong rows.
  
  Fixed by creating temporary table for self-joined multi update statement.

  mysql-test/r/myisam.result@stripped, 2006-11-23 19:50:35+04:00, svoj@stripped +16 -0
    A test case for BUG#21310.

  mysql-test/t/myisam.test@stripped, 2006-11-23 19:50:36+04:00, svoj@stripped +19 -0
    A test case for BUG#21310.

  sql/sql_update.cc@stripped, 2006-11-23 19:50:36+04:00, svoj@stripped +11 -23
    Disabling record cache for self-joined multi update statement is wrong.
    The join must only see the table as it was at the beginning of the statement.
    safe_update_on_fly check if it is safe to update first table on the fly, that is
    not creating temporary table. It is possible in case a row from this table is
    never read more than once. safe_update_on_fly now detect self-joined table and
    refuse to update this table on the fly.

# 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:	svoj
# Host:	april.(none)
# Root:	/home/svoj/devel/mysql/BUG21310/mysql-4.1-engines

--- 1.157/sql/sql_update.cc	2006-11-23 19:50:41 +04:00
+++ 1.158/sql/sql_update.cc	2006-11-23 19:50:41 +04:00
@@ -23,7 +23,8 @@
 #include "mysql_priv.h"
 #include "sql_select.h"
 
-static bool safe_update_on_fly(JOIN_TAB *join_tab, List<Item> *fields);
+static bool safe_update_on_fly(THD *thd, JOIN_TAB *join_tab,
+                               TABLE_LIST *update_tables, List<Item> *fields);
 
 /* Return 0 if row hasn't changed */
 
@@ -846,26 +847,6 @@ int multi_update::prepare(List<Item> &no
   for (i=0 ; i < table_count ; i++)
     set_if_bigger(max_fields, fields_for_table[i]->elements);
   copy_field= new Copy_field[max_fields];
-
-  /*
-    Mark all copies of tables that are updates to ensure that
-    init_read_record() will not try to enable a cache on them
-
-    The problem is that for queries like
-
-    UPDATE t1, t1 AS t2 SET t1.b=t2.c WHERE t1.a=t2.a;
-
-    the row buffer may contain things that doesn't match what is on disk
-    which will cause an error when reading a row.
-    (This issue is mostly relevent for MyISAM tables)
-  */
-  for (table_ref= all_tables;  table_ref; table_ref=table_ref->next)
-  {
-    TABLE *table=table_ref->table;
-    if ((tables_to_update & table->map) && 
-	mysql_lock_have_duplicate(thd, table, update_tables))
-      table->no_cache= 1;			// Disable row cache
-  }
   DBUG_RETURN(thd->is_fatal_error != 0);
 }
 
@@ -905,7 +886,7 @@ multi_update::initialize_tables(JOIN *jo
       table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
     if (table == main_table)			// First table in join
     {
-      if (safe_update_on_fly(join->join_tab, &temp_fields))
+      if (safe_update_on_fly(thd, join->join_tab, update_tables, &temp_fields))
       {
 	table_to_update= main_table;		// Update table on the fly
 	continue;
@@ -957,6 +938,7 @@ multi_update::initialize_tables(JOIN *jo
   SYNOPSIS
     safe_update_on_fly
     join_tab		How table is used in join
+    update_tables       List of tables that will be updated
     fields		Fields that are updated
 
   NOTES
@@ -970,6 +952,8 @@ multi_update::initialize_tables(JOIN *jo
     - We are doing a range scan and we don't update the scan key or
       the primary key for a clustered table handler.
 
+    - Table is not joined to itself.
+
   WARNING
     This code is a bit dependent of how make_join_readinfo() works.
 
@@ -978,9 +962,13 @@ multi_update::initialize_tables(JOIN *jo
     1		Safe to update
 */
 
-static bool safe_update_on_fly(JOIN_TAB *join_tab, List<Item> *fields)
+static bool safe_update_on_fly(THD *thd, JOIN_TAB *join_tab,
+                               TABLE_LIST *update_tables, List<Item> *fields)
 {
   TABLE *table= join_tab->table;
+  /* First check if a table is not joined to itself. */
+  if (mysql_lock_have_duplicate(thd, table, update_tables))
+    return 0;
   switch (join_tab->type) {
   case JT_SYSTEM:
   case JT_CONST:

--- 1.68/mysql-test/r/myisam.result	2006-11-23 19:50:41 +04:00
+++ 1.69/mysql-test/r/myisam.result	2006-11-23 19:50:41 +04:00
@@ -944,3 +944,19 @@ select * from t1;
 a
 42
 drop table t1;
+CREATE TABLE t1(a VARCHAR(16));
+INSERT INTO t1 VALUES('aaaaaaaa'),(NULL);
+UPDATE t1 AS ta1, t1 AS ta2 SET ta1.a='aaaaaaaaaaaaaaaa';
+SELECT * FROM t1;
+a
+aaaaaaaaaaaaaaaa
+aaaaaaaaaaaaaaaa
+DROP TABLE t1;
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(1),(2);
+UPDATE t1,t1 AS t2 SET t1.a=t1.a+2 WHERE t1.a=t2.a-1;
+SELECT * FROM t1 ORDER BY a;
+a
+2
+3
+DROP TABLE t1;

--- 1.54/mysql-test/t/myisam.test	2006-11-23 19:50:41 +04:00
+++ 1.55/mysql-test/t/myisam.test	2006-11-23 19:50:41 +04:00
@@ -890,4 +890,23 @@ connection default;
 select * from t1;
 drop table t1;
 
+#
+# BUG#21310 - Trees in SQL causing a "crashed" table with MyISAM storage
+#             engine
+#
+
+# A simplified test case that reflect crashed table issue.
+CREATE TABLE t1(a VARCHAR(16));
+INSERT INTO t1 VALUES('aaaaaaaa'),(NULL);
+UPDATE t1 AS ta1, t1 AS ta2 SET ta1.a='aaaaaaaaaaaaaaaa';
+SELECT * FROM t1;
+DROP TABLE t1;
+
+# A test case that reflect wrong result set.
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(1),(2);
+UPDATE t1,t1 AS t2 SET t1.a=t1.a+2 WHERE t1.a=t2.a-1;
+SELECT * FROM t1 ORDER BY a;
+DROP TABLE t1;
+
 # End of 4.1 tests