Hi, Thirunarayanan! On Dec 13, Thirunarayanan Balathandayuthapani wrote:

revision-id: c16ad313bc4 (mariadb-10.2.19-4-gc16ad313bc4) parent(s): 7e756437789 author: Thirunarayanan Balathandayuthapani <thiru@mariadb.com> committer: Thirunarayanan Balathandayuthapani <thiru@mariadb.com> timestamp: 2018-11-15 15:14:02 +0530 message:

MDEV-16849 Extending indexed VARCHAR column should be instantaneous ... diff --git a/mysql-test/suite/innodb/r/alter_varchar_change.result b/mysql-test/suite/innodb/r/alter_varchar_change.result new file mode 100644 index 00000000000..5d2c6403aab --- /dev/null +++ b/mysql-test/suite/innodb/r/alter_varchar_change.result @@ -0,0 +1,335 @@ ... +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; +@tbl1_id = @tbl_id +1 +SELECT @idx1_id = @idx_id; +@idx1_id = @idx_id +1

Is that right? Old index would sort values "aaaaaaaaaa1", "aaaaaaaaaa2", "aaaaaaaaaa3" as equal, so they could be in the index in any order. But in the new index they aren't equal.

+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);

please, add a case where there's a FULLTEXT index, as above, but ALTER TABLE makes a column shorter. The index must be rebuilt.

+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;

Please also add a test case where VARCHAR is made shorter, but still longer than a prefix: ALTER TABLE t1 MODIFY f2 VARCHAR(50) The index should not be rebuilt. And shorter than a prefix: ALTER TABLE t1 MODIFY f2 VARCHAR(5) The index must be rebuilt. Also add a test when ALTER TABLE changes column's charset, or column type (CHAR/VARCHAR/TEXT). And a test where column's length is changed over 255. E.g. from 200 to 300.

diff --git a/sql/sql_table.cc b/sql/sql_table.cc --- a/sql/sql_table.cc +++ b/sql/sql_table.cc @@ -6687,18 +6687,28 @@ 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) + if (key_part->length <= new_part->length && + old_field->pack_length() < new_field->pack_length &&

I still don't understand this condition. Why do you care whether a field length has changed, while you're should interested to know whether an index length have changed? Field length changes are completely irrelevant here. again, the only possible ALTER_COLUMN_INDEX_LENGTH case: * key part length was the same as column length, and it was not decreased. So, your condition should, probably, be something like if (key_part->length == old_field->pack_length() && 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;

- new_field= get_field_by_index(alter_info, new_part->fieldnr); - /* For prefix keys KEY_PART_INFO::field points to cloned Field object with adjusted length. So below we have to check field

Regards, Sergei Chief Architect MariaDB and security@mariadb.org