MDEV-16849 Extending indexed VARCHAR column should be instantaneousbb-10.2-MDEV-16849

- Addressed Serg's review comments again.

- If column length is decreased then the table will be rebuild.
So removed the un-necessary index id comparison to avoid confusion
in test case.

- Set the column index length flag if only index length is increased.

3 files changed, 5 insertions, 12 deletions

diff --git a/mysql-test/suite/innodb/r/alter_varchar_change.result b/mysql-test/suite/innodb/r/alter_varchar_change.result
index 2f412aecbf1..0b06fddd35e 100644
--- a/mysql-test/suite/innodb/r/alter_varchar_change.result
+++ b/mysql-test/suite/innodb/r/alter_varchar_change.result
@@ -319,20 +319,18 @@ f2 VARCHAR(100),
 INDEX idx(f2(10)),
 INDEX idx1(f1))ENGINE=InnoDB;
 CALL get_table_id("test/t1", @tbl_id);
-ALTER TABLE t1 MODIFY f2 VARCHAR(50), DROP INDEX idx1;
+ALTER TABLE t1 MODIFY f2 VARCHAR(50);
 CALL get_table_id("test/t1", @tbl1_id);
 SELECT @tbl1_id = @tbl_id;
 @tbl1_id = @tbl_id
 0
-SELECT @idx1_id = @idx_id;
-@idx1_id = @idx_id
-0
 SHOW CREATE TABLE t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `f1` int(11) NOT NULL,
   `f2` varchar(50) DEFAULT NULL,
-  KEY `idx` (`f2`(10))
+  KEY `idx` (`f2`(10)),
+  KEY `idx1` (`f1`)
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 DROP TABLE t1;
 CREATE TABLE t1(f1 INT NOT NULL,
@@ -345,9 +343,6 @@ CALL get_table_id("test/t1", @tbl1_id);
 SELECT @tbl1_id = @tbl_id;
 @tbl1_id = @tbl_id
 0
-SELECT @idx1_id = @idx_id;
-@idx1_id = @idx_id
-0
 SHOW CREATE TABLE t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
diff --git a/mysql-test/suite/innodb/t/alter_varchar_change.test b/mysql-test/suite/innodb/t/alter_varchar_change.test
index 508ebbabf32..f435125e581 100644
--- a/mysql-test/suite/innodb/t/alter_varchar_change.test
+++ b/mysql-test/suite/innodb/t/alter_varchar_change.test
@@ -236,11 +236,10 @@ CREATE TABLE t1(f1 INT NOT NULL,
 		INDEX idx1(f1))ENGINE=InnoDB;
 
 CALL get_table_id("test/t1", @tbl_id);
-ALTER TABLE t1 MODIFY f2 VARCHAR(50), DROP INDEX idx1;
+ALTER TABLE t1 MODIFY f2 VARCHAR(50);
 CALL get_table_id("test/t1", @tbl1_id);
 
 SELECT @tbl1_id = @tbl_id;
-SELECT @idx1_id = @idx_id;
 SHOW CREATE TABLE t1;
 DROP TABLE t1;
 
@@ -254,7 +253,6 @@ ALTER TABLE t1 MODIFY f2 VARCHAR(5), DROP INDEX idx1;
 CALL get_table_id("test/t1", @tbl1_id);
 
 SELECT @tbl1_id = @tbl_id;
-SELECT @idx1_id = @idx_id;
 SHOW CREATE TABLE t1;
 DROP TABLE t1;
 
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 7eca33812b9..3673a373931 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -6708,7 +6708,7 @@ static bool fill_alter_inplace_info(THD *thd,
       }
 
       if (key_part->length == old_field_len &&
-          key_part->length <= new_part->length &&
+          key_part->length < new_part->length &&
 	  (key_part->field->is_equal((Create_field*) new_field)
            == IS_EQUAL_PACK_LENGTH))
       {