From 5c0cdea62341da75f0560216af1b363b156ed1ab Mon Sep 17 00:00:00 2001
From: unknown <svoj@may.pils.ru>
Date: Wed, 21 Jun 2006 17:30:59 +0500
Subject: [PATCH] BUG#20357 - Got error 124 from storage engine using MIN and
 MAX             functions in queries

Using MAX()/MIN() on table with disabled indexes (by ALTER TABLE)
results in error 124 (wrong index) from storage engine.

The problem was that optimizer use disabled index to optimize
MAX()/MIN(). Normally it must skip disabled index and perform
table scan.

This patch skips disabled indexes for min/max optimization.


mysql-test/r/myisam.result:
  Test case for BUG#20357.
mysql-test/t/myisam.test:
  Test case for BUG#20357.
sql/opt_sum.cc:
  Skip disabled/ignored indexes for min/max optimization.
---
 mysql-test/r/myisam.result | 13 +++++++++++++
 mysql-test/t/myisam.test   | 12 ++++++++++++
 sql/opt_sum.cc             |  6 ++++++
 3 files changed, 31 insertions(+)

diff --git a/mysql-test/r/myisam.result b/mysql-test/r/myisam.result
index 3b4519e5444..91a5bb08c0f 100644
--- a/mysql-test/r/myisam.result
+++ b/mysql-test/r/myisam.result
@@ -748,3 +748,16 @@ select count(id1) from t1 where id2 = 10;
 count(id1)
 5
 drop table t1;
+CREATE TABLE t1(a TINYINT, KEY(a)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES(1);
+SELECT MAX(a) FROM t1 IGNORE INDEX(a);
+MAX(a)
+1
+ALTER TABLE t1 DISABLE KEYS;
+SELECT MAX(a) FROM t1;
+MAX(a)
+1
+SELECT MAX(a) FROM t1 IGNORE INDEX(a);
+MAX(a)
+1
+DROP TABLE t1;
diff --git a/mysql-test/t/myisam.test b/mysql-test/t/myisam.test
index 7e4cc324b12..06f913111d3 100644
--- a/mysql-test/t/myisam.test
+++ b/mysql-test/t/myisam.test
@@ -705,4 +705,16 @@ select count(*)   from t1 where id2 = 10;
 select count(id1) from t1 where id2 = 10;
 drop table t1;
 
+#
+# BUG##20357 - Got error 124 from storage engine using MIN and MAX functions
+#              in queries
+#
+CREATE TABLE t1(a TINYINT, KEY(a)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES(1);
+SELECT MAX(a) FROM t1 IGNORE INDEX(a);
+ALTER TABLE t1 DISABLE KEYS;
+SELECT MAX(a) FROM t1;
+SELECT MAX(a) FROM t1 IGNORE INDEX(a);
+DROP TABLE t1;
+
 # End of 4.1 tests
diff --git a/sql/opt_sum.cc b/sql/opt_sum.cc
index cfb5b3695a3..63373a8579a 100644
--- a/sql/opt_sum.cc
+++ b/sql/opt_sum.cc
@@ -673,6 +673,12 @@ static bool find_key_for_maxmin(bool max_fl, TABLE_REF *ref,
   {
     KEY_PART_INFO *part,*part_end;
     key_part_map key_part_to_use= 0;
+    /*
+      Perform a check if index is not disabled by ALTER TABLE
+      or IGNORE INDEX.
+    */
+    if (!table->keys_in_use_for_query.is_set(idx))
+      continue;
     uint jdx= 0;
     *prefix_len= 0;
     for (part= keyinfo->key_part, part_end= part+keyinfo->key_parts ;