bk commit into 5.1 tree (mhansson:1.2359) BUG#20604

[mhansson]

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ChangeSet@stripped, 2007-01-11 12:18:06+01:00, mhansson@stripped +3 -0
  BUG # 20604
  
  Fixed
  
  The function that checks whether we can use keys for aggregates,
  find_key_for_maxmin(), fails to check that keys are not disabled by
  ALTER TABLE.
  
  The fact that keys are disabled does not reveal itself in
  keys_in_use_for_query, but rather in a field in its "table share", called
  keys_in_use. The reasoning behind this is most likely that
  a DISABLE KEYS is set on table level, as opposed to a
  particular projection of a table. 
  
  Table level objects are known as "table shares" inside the code.
  
  Projections of tables are known in the code as a "table".
  
  Hence the set of indexes that can be used are the intersection of
  those that this particular "table" object permits using and those that
  the "table share" permits using.

  mysql-test/r/key.result@stripped, 2007-01-11 12:18:04+01:00, mhansson@stripped +7 -0
    This is the correct output for this query. It isn't actually that important because
this 
    set of commands will actually cause a failure to be reported from MyISAM when the bug 
    is active.

  mysql-test/t/key.test@stripped, 2007-01-11 12:18:04+01:00, mhansson@stripped +11 -0
    The minimal test case that reveals the bug. The optimizer for aggregates did not take 
    into account that keys might be the disabled on a table. The execution engine then
tries 
    to proceed and use the index, causing MyISAM to crash.

  sql/opt_sum.cc@stripped, 2007-01-11 12:18:04+01:00, mhansson@stripped +3 -1
    This shows where the aggregate optimizer decides which indexes it is free to use. 
    
    The comment preceding "if (!enabled_keys.is_set(idx))" was actually incorrect, because
the algorithm 
    did not look at whether keys where disabled via ALTER TABLE or not.

# 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:	mhansson
# Host:	linux-st28.site
# Root:	/home/martin/mysql/src/5.1o-dbg-bug20604

--- 1.58/sql/opt_sum.cc	2006-10-18 10:47:17 +02:00
+++ 1.59/sql/opt_sum.cc	2007-01-11 12:18:04 +01:00
@@ -743,6 +743,8 @@
   uint idx= 0;
 
   KEY *keyinfo,*keyinfo_end;
+  key_map enabled_keys= table->s->keys_in_use;
+  enabled_keys.intersect(table->keys_in_use_for_query);
   for (keyinfo= table->key_info, keyinfo_end= keyinfo+table->s->keys ;
        keyinfo != keyinfo_end;
        keyinfo++,idx++)
@@ -753,7 +755,7 @@
       Perform a check if index is not disabled by ALTER TABLE
       or IGNORE INDEX.
     */
-    if (!table->keys_in_use_for_query.is_set(idx))
+    if (!enabled_keys.is_set(idx))
       continue;
     uint jdx= 0;
     *prefix_len= 0;

--- 1.40/mysql-test/r/key.result	2006-08-11 23:06:20 +02:00
+++ 1.41/mysql-test/r/key.result	2007-01-11 12:18:04 +01:00
@@ -482,3 +482,10 @@
 alter table t1 add index i3 (c3), add index i2 (c2), add unique index i1 (c1);
 ERROR 23000: Duplicate entry '1' for key 'i1'
 drop table t1;
+CREATE TABLE t1( a TINYINT, KEY(a) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES( 1 );
+ALTER TABLE t1 DISABLE KEYS;
+SELECT MAX(a) FROM t1 FORCE INDEX(a);
+MAX(a)
+1
+drop table t1;

--- 1.31/mysql-test/t/key.test	2006-07-20 20:41:52 +02:00
+++ 1.32/mysql-test/t/key.test	2007-01-11 12:18:04 +01:00
@@ -442,3 +442,14 @@
 alter table t1 add index i3 (c3), add index i2 (c2), add unique index i1 (c1);
 drop table t1;
 
+#
+# Bug #20604: Test for disabled keys with aggregate functions and FORCE INDEX.
+#
+
+CREATE TABLE t1( a TINYINT, KEY(a) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES( 1 );
+ALTER TABLE t1 DISABLE KEYS;
+SELECT MAX(a) FROM t1 FORCE INDEX(a);
+
+drop table t1;
+