Bug#20755615 CREATING INDEX ON A RENAMED COLUMN WITH CASE CRASH .FRM

                FILE

PROBLEM

In 5.5 when doing doing a rename of a column ,we ignore the case between
old and new column names while comparing them,so if the change is just
the case then we don't even mark the field FIELD_IS_RENAMED ,we just update
the frm file ,but don't recreate the table as is the norm when alter is
used.This leads to inconsistency in the innodb data dictionary which causes
index creation to fail.

FIX

According to the documentation any innodb column rename should trigger
rebuild of the table. Therefore for innodb tables we will do a strcmp()
between the column names and if there is case change in column name
we will trigger a rebuild.

mysql-test/r/alter_table.result

@@ -1488,3 +1488,20 @@ CREATE TABLE help_topic (dummy int) ENGINE=innodb;
 ERROR HY000: Storage engine 'InnoDB' does not support system tables. [mysql.help_topic]
 use test;
 # End of Bug#11815557
+#
+# Bug#20755615	CREATING INDEX ON A RENAMED
+#                COLUMN WITH CASE CRASH .FRM FILE
+#
+CREATE TABLE t1 (D INT) ENGINE=innodb;
+INSERT INTO t1 VALUES (10);
+ALTER TABLE t1 MODIFY COLUMN d INT;
+ALTER TABLE t1 ADD INDEX (d);
+DROP TABLE t1;
+CREATE TABLE t1 (`` int) ENGINE=innodb;
+INSERT INTO t1 VALUES (10);
+ALTER TABLE t1 CHANGE `` `` INT;
+ALTER TABLE t1 ADD INDEX (``);
+SELECT * FROM t1;
+
+10
+DROP TABLE t1;

mysql-test/t/alter_table.test

@@ -1261,3 +1261,22 @@ CREATE TABLE time_zone (dummy int) ENGINE=merge;
 CREATE TABLE help_topic (dummy int) ENGINE=innodb;
 use test;
 --echo # End of Bug#11815557
+
+--echo #
+--echo # Bug#20755615	CREATING INDEX ON A RENAMED
+--echo #                COLUMN WITH CASE CRASH .FRM FILE
+--echo #
+
+CREATE TABLE t1 (D INT) ENGINE=innodb;
+INSERT INTO t1 VALUES (10);
+ALTER TABLE t1 MODIFY COLUMN d INT;
+ALTER TABLE t1 ADD INDEX (d);
+DROP TABLE t1;
+
+CREATE TABLE t1 (`` int) ENGINE=innodb;
+INSERT INTO t1 VALUES (10);
+ALTER TABLE t1 CHANGE `` `` INT;
+ALTER TABLE t1 ADD INDEX (``);
+SELECT * FROM t1;
+DROP TABLE t1;
+

sql/sql_table.cc

@@ -5048,10 +5048,22 @@ mysql_compare_tables(TABLE *table,
 
     /* Check if field was renamed */
     field->flags&= ~FIELD_IS_RENAMED;
-    if (my_strcasecmp(system_charset_info,
-		      field->field_name,
-		      tmp_new_field->field_name))
-      field->flags|= FIELD_IS_RENAMED;      
+
+    /*
+      InnoDB data dictionary is case sensitive so we should use string case
+      sensitive comparison between fields. Note: strcmp branch is to be
+      removed in future when we fix it in InnoDB.
+    */
+    if ((table->s->db_type())->db_type == DB_TYPE_INNODB &&
+         strcmp(field->field_name,tmp_new_field->field_name))
+      field->flags|= FIELD_IS_RENAMED;
+    else
+    {
+      if (my_strcasecmp(system_charset_info,
+                        field->field_name,
+                        tmp_new_field->field_name))
+        field->flags|= FIELD_IS_RENAMED;
+    }
 
     /* Evaluate changes bitmap and send to check_if_incompatible_data() */
     if (!(tmp= field->is_equal(tmp_new_field)))