bk commit into 5.0 tree (jimw:1.1839) BUG#10543

[Jim Winstead]

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5.0 repository of jimw. When jimw does a push these changes will
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ChangeSet
  1.1839 05/05/17 15:48:09 jimw@stripped +3 -0
  Fix preserving prefix of keys when converting VARCHAR to TEXT.
  (Bug #10543)

  sql/sql_table.cc
    1.246 05/05/17 15:48:06 jimw@stripped +40 -6
    Only reset the length of a key part when changing from a
    non-prefixable key to a prefixable-key or vice versa, or
    when the prefix is smaller than the length of the field.

  mysql-test/t/type_varchar.test
    1.6 05/05/17 15:48:06 jimw@stripped +12 -0
    Add test for bug #10543

  mysql-test/r/type_varchar.result
    1.6 05/05/17 15:48:06 jimw@stripped +23 -0
    Add results

# 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:	jimw
# Host:	rama.(none)
# Root:	/home/jimw/my/mysql-5.0-10543

--- 1.245/sql/sql_table.cc	2005-05-16 05:21:31 -07:00
+++ 1.246/sql/sql_table.cc	2005-05-17 15:48:06 -07:00
@@ -2965,6 +2965,34 @@
 
 
 /*
+  Check whether a field type can have a prefixed key
+
+  SYNOPSIS
+   type_can_have_prefix_key()
+   type                 field type
+
+  RETURN
+    TRUE  Type can have a prefixed key
+    FALSE Type can not have a prefixed key
+*/
+
+static bool type_can_have_prefix_key(enum enum_field_types type)
+{
+  switch (type) {
+  case MYSQL_TYPE_VARCHAR:
+  case MYSQL_TYPE_TINY_BLOB:
+  case MYSQL_TYPE_MEDIUM_BLOB:
+  case MYSQL_TYPE_LONG_BLOB:
+  case MYSQL_TYPE_BLOB:
+  case MYSQL_TYPE_VAR_STRING:
+  case MYSQL_TYPE_STRING:
+    return true;
+  default:
+    return false;
+  }
+}
+
+/*
   Alter table
 */
 
@@ -3334,12 +3362,18 @@
 	continue;				// Field is removed
       uint key_part_length=key_part->length;
       if (cfield->field)			// Not new field
-      {						// Check if sub key
-	if (cfield->field->type() != FIELD_TYPE_BLOB &&
-	    (cfield->field->pack_length() == key_part_length ||
-	     cfield->length <= key_part_length /
-			       key_part->field->charset()->mbmaxlen))
-	  key_part_length=0;			// Use whole field
+      {
+        /*
+          If the field can't have a prefix according to its new type, or
+          should not have a prefix according to its previous type, or the
+          field length is less than the prefix length, unset the prefix
+          length.
+         */
+        if (!type_can_have_prefix_key(cfield->field->type()) ||
+            !type_can_have_prefix_key(cfield->sql_type) ||
+	    (cfield->length && (cfield->length < key_part_length /
+                                key_part->field->charset()->mbmaxlen)))
+	  key_part_length= 0;			// Use whole field
       }
       key_part_length /= key_part->field->charset()->mbmaxlen;
       key_parts.push_back(new key_part_spec(cfield->field_name,

--- 1.5/mysql-test/r/type_varchar.result	2005-04-21 09:06:02 -07:00
+++ 1.6/mysql-test/r/type_varchar.result	2005-05-17 15:48:06 -07:00
@@ -392,3 +392,26 @@
 a	b	min(t1.b)
 22	NULL	NULL
 drop table t1, t2;
+create table t1 (f1 varchar(65500));
+create index index1 on t1(f1(10));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` varchar(65500) default NULL,
+  KEY `index1` (`f1`(10))
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+alter table t1 modify f1 varchar(255);
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` varchar(255) default NULL,
+  KEY `index1` (`f1`(10))
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+alter table t1 modify f1 tinytext;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` tinytext,
+  KEY `index1` (`f1`(10))
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;

--- 1.5/mysql-test/t/type_varchar.test	2005-04-21 09:06:02 -07:00
+++ 1.6/mysql-test/t/type_varchar.test	2005-05-17 15:48:06 -07:00
@@ -118,3 +118,15 @@
 select t1.a, t1.b, min(t1.b) from t1 inner join t2 ON t2.a = t1.a 
   group by t1.b, t1.a;
 drop table t1, t2;
+
+#
+# Bug #10543: convert varchar with index to text
+#
+create table t1 (f1 varchar(65500));
+create index index1 on t1(f1(10));
+show create table t1;
+alter table t1 modify f1 varchar(255);
+show create table t1;
+alter table t1 modify f1 tinytext;
+show create table t1;
+drop table t1;