MDEV-16849 Extending indexed VARCHAR column should be instantaneous

Analysis:
========
Increasing the length of the indexed varchar column is not an instant operation for
innodb.

Fix:
===
- Introduce the new handler flag 'Alter_inplace_info::ALTER_COLUMN_INDEX_LENGTH' to
indicate the index length differs due to change of column length changes.

- InnoDB makes the ALTER_COLUMN_INDEX_LENGTH flag as instant operation.

This is a port of Mysql fix.

    commit 913071c0b16cc03e703308250d795bc381627e37
    Author: Nisha Gopalakrishnan <nisha.gopalakrishnan@oracle.com>
    Date:   Wed May 30 14:54:46 2018 +0530

        BUG#26848813: INDEXED COLUMN CAN'T BE CHANGED FROM VARCHAR(15)
                      TO VARCHAR(40) INSTANTANEOUSLY

mysql-test/suite/innodb/t/alter_varchar_change.test

+--source include/have_innodb.inc
+
+DELIMITER |;
+CREATE PROCEDURE get_index_id(IN tbl_id INT, IN idx_name char(100), OUT idx_id INT)
+BEGIN
+SELECT index_id into idx_id FROM INFORMATION_SCHEMA.INNODB_SYS_INDEXES WHERE
+	NAME=idx_name and TABLE_ID=tbl_id;
+END|
+
+CREATE PROCEDURE get_table_id(IN tbl_name char(100), OUT tbl_id INT)
+BEGIN
+SELECT table_id into tbl_id FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES WHERE
+	NAME = tbl_name;
+END|
+
+DELIMITER ;|
+
+SET @tbl_id = 0;
+SET @tbl1_id = 0;
+SET @idx_id = 0;
+SET @idx1_id = 0;
+
+# Table should avoid rebuild for the following varchar change.
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100) PRIMARY KEY)ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200);
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+# Index should avoid rebuild
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200);
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL, f2 VARCHAR(100), f3 VARCHAR(100),
+		INDEX idx(f2, f3), index idx1(f3, f2))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), MODIFY f3 VARCHAR(150);
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL, f2 VARCHAR(100),
+		INDEX idx(f2(40)))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200);
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100), FULLTEXT idx(f2))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200);
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		f3 VARCHAR(50) as (f2) VIRTUAL,
+		INDEX idx(f3))ENGINE=InnoDB;
+
+INSERT INTO t1(f1, f2) VALUES(1, repeat('a', 40));
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(100);
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2(10)),
+		INDEX idx1(f1))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), DROP INDEX idx1;
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2(10)))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), DROP INDEX idx, ADD INDEX idx(f2(10));
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2(10)))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), DROP INDEX idx, ADD INDEX idx(f2(50));
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+# Newly added index should built
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2(100)))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), ADD INDEX idx1(f1);
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2(10)))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), DROP INDEX idx, ADD INDEX idx(f2(6));
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+# Table should rebuild
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), ADD COLUMN f3 INT;
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL, f2 VARCHAR(100) PRIMARY KEY)ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), ADD COLUMN f3 INT;
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL, f2 VARCHAR(100))ENGINE=INNODB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200), ADD FULLTEXT idx(f2);
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 CHAR(100) PRIMARY KEY)ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 CHAR(200);
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		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);
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		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(5), DROP INDEX idx1;
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100), FULLTEXT idx(f2))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+CALL get_index_id(@tbl_id, "idx", @idx_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(50);
+CALL get_table_id("test/t1", @tbl1_id);
+CALL get_index_id(@tbl1_id, "idx", @idx1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SELECT @idx1_id = @idx_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 CHAR(200);
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2(40)))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 TEXT;
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2(40)))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(300);
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		INDEX idx(f2(40)))ENGINE=InnoDB;
+
+CALL get_table_id("test/t1", @tbl_id);
+ALTER TABLE t1 MODIFY f2 VARCHAR(200) CHARACTER SET UTF16;
+CALL get_table_id("test/t1", @tbl1_id);
+
+SELECT @tbl1_id = @tbl_id;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+# Show error when virtual varchar column got changed
+
+CREATE TABLE t1(f1 INT NOT NULL,
+		f2 VARCHAR(100),
+		f3 VARCHAR(50) as (f2) VIRTUAL,
+		INDEX idx(f3))ENGINE=InnoDB;
+
+--echo # If varchar virtual column extension is allowed in the future then
+--echo #	InnoDB must rebuild the index
+
+--error ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN
+ALTER TABLE t1 MODIFY f3 VARCHAR(100);
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+DROP PROCEDURE get_index_id;
+DROP PROCEDURE get_table_id;

sql/handler.h

@@ -2001,6 +2001,11 @@ class Alter_inplace_info
 
   static const HA_ALTER_FLAGS ALTER_DROP_CHECK_CONSTRAINT= 1ULL << 40;
 
+  /**
+    Change in index length such that it doesn't require index rebuild.
+  */
+  static const HA_ALTER_FLAGS ALTER_COLUMN_INDEX_LENGTH= 1ULL << 41;
+
   /**
     Create options (like MAX_ROWS) for the new version of table.
 

sql/sql_table.cc

@@ -6303,7 +6303,7 @@ static bool fill_alter_inplace_info(THD *thd,
                                     bool varchar,
                                     Alter_inplace_info *ha_alter_info)
 {
-  Field **f_ptr, *field;
+  Field **f_ptr, *field, *old_field;
   List_iterator_fast<Create_field> new_field_it;
   Create_field *new_field;
   KEY_PART_INFO *key_part, *new_part;
@@ -6629,6 +6629,7 @@ static bool fill_alter_inplace_info(THD *thd,
     Go through keys and check if the original ones are compatible
     with new table.
   */
+  uint old_field_len= 0;
   KEY *table_key;
   KEY *table_key_end= table->key_info + table->s->keys;
   KEY *new_key;
@@ -6693,17 +6694,35 @@ static bool fill_alter_inplace_info(THD *thd,
          key_part < end;
          key_part++, new_part++)
     {
+      new_field= get_field_by_index(alter_info, new_part->fieldnr);
+      old_field= table->field[key_part->fieldnr - 1];
       /*
+        If there is a change in index length due to column expansion
+        like varchar(X) changed to varchar(X + N) and has a compatible
+        packed data representation, we mark it for fast/INPLACE change
+        in index definition. InnoDB supports INPLACE for this cases
+
         Key definition has changed if we are using a different field or
-        if the used key part length is different. It makes sense to
-        check lengths first as in case when fields differ it is likely
-        that lengths differ too and checking fields is more expensive
-        in general case.
+        if the user key part length is different.
       */
-      if (key_part->length != new_part->length)
-        goto index_changed;
+      old_field_len= old_field->pack_length();
 
-      new_field= get_field_by_index(alter_info, new_part->fieldnr);
+      if (old_field->type() == MYSQL_TYPE_VARCHAR)
+      {
+        old_field_len= (old_field->pack_length()
+                        - ((Field_varstring*) old_field)->length_bytes);
+      }
+
+      if (key_part->length == old_field_len &&
+          key_part->length < new_part->length &&
+	  (key_part->field->is_equal((Create_field*) new_field)
+           == IS_EQUAL_PACK_LENGTH))
+      {
+        ha_alter_info->handler_flags |=
+           Alter_inplace_info::ALTER_COLUMN_INDEX_LENGTH;
+      }
+      else if (key_part->length != new_part->length)
+        goto index_changed;
 
       /*
         For prefix keys KEY_PART_INFO::field points to cloned Field

storage/innobase/handler/handler0alter.cc

@@ -90,7 +90,8 @@ static const Alter_inplace_info::HA_ALTER_FLAGS INNOBASE_INPLACE_IGNORE
 	| Alter_inplace_info::ALTER_COLUMN_COLUMN_FORMAT
 	| Alter_inplace_info::ALTER_COLUMN_STORAGE_TYPE
 	| Alter_inplace_info::ALTER_VIRTUAL_GCOL_EXPR
-	| Alter_inplace_info::ALTER_RENAME;
+	| Alter_inplace_info::ALTER_RENAME
+	| Alter_inplace_info::ALTER_COLUMN_INDEX_LENGTH;
 
 /** Operations on foreign key definitions (changing the schema only) */
 static const Alter_inplace_info::HA_ALTER_FLAGS INNOBASE_FOREIGN_OPERATIONS