Hi, Thirunarayanan!
On Nov 05, Thirunarayanan Balathandayuthapani wrote:
> revision-id: 5403baabc7ef87e301964434e3670ded06af0802
> (mariadb-10.2.18-40-g5403baabc7e)
> parent(s): ab1ce2204e959bea596817494e932754ab5cbe88
> author: Thirunarayanan Balathandayuthapani <th...@mariadb.com>
> committer: Thirunarayanan Balathandayuthapani <th...@mariadb.com>
> timestamp: 2018-10-26 16:49:08 +0530
> message:
>
> 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.
>
> diff --git a/sql/handler.cc b/sql/handler.cc
> index da41daf2440..b1fa53fb145 100644
> --- a/sql/handler.cc
> +++ b/sql/handler.cc
> @@ -4253,7 +4253,8 @@ handler::check_if_supported_inplace_alter(TABLE
> *altered_table,
> Alter_inplace_info::CHANGE_CREATE_OPTION |
> Alter_inplace_info::ALTER_PARTITIONED |
> Alter_inplace_info::ALTER_VIRTUAL_GCOL_EXPR |
> - Alter_inplace_info::ALTER_RENAME;
> + Alter_inplace_info::ALTER_RENAME |
> + Alter_inplace_info::ALTER_COLUMN_INDEX_LENGTH;
You sure? It means that any engine by default can do
ALTER_COLUMN_INDEX_LENGTH inplace, unless some other check in the engine
disallows it.
I'd rather not enable it for all engine, so better remove it.
InnoDB has his own check inside
ha_innobase::check_if_supported_inplace_alter() anyway.
> /* Is there at least one operation that requires copy algorithm? */
> if (ha_alter_info->handler_flags & ~inplace_offline_operations)
> diff --git a/sql/handler.h b/sql/handler.h
> index ed2ef822c88..f2250699cfb 100644
> --- a/sql/handler.h
> +++ b/sql/handler.h
> @@ -1994,6 +1994,11 @@ 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.
>
> diff --git a/sql/sql_table.cc b/sql/sql_table.cc
> index 02780e7d1e0..94d35c99d0a 100644
> --- a/sql/sql_table.cc
> +++ b/sql/sql_table.cc
> @@ -6687,18 +6687,27 @@ 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);
> /*
> + 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 &&
> + (ha_alter_info->alter_info->flags &
> Alter_info::ALTER_CHANGE_COLUMN) &&
why is that? Can it happen that ALTER_CHANGE_COLUMN flag is not set?
> + (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 secur...@mariadb.org
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