Remove alter_algorithm but keep the variable as no-op (with a warning).
The reasons for removing alter_algorithm are:
- alter_algorithm was introduced as a replacement for the
old_alter_table that was used to force the usage of the original
alter table algorithm (copy) in the cases where the new alter
algorithm did not work. The new option was added as a way to force
the usage of a specific algorithm when it should instead have made
it possible to disable algorithms that would not work for some
reason.
- alter_algorithm introduced some cases where ALTER TABLE would not
work without specifying the ALGORITHM=XXX option together with
ALTER TABLE.
- Having different values of alter_algorithm on master and slave could
cause slave to stop unexpectedly.
- ALTER TABLE FORCE, as used by mariadb-upgrade, would not always work
if alter_algorithm was set for the server.
- As part of the MDEV-33449 "improving repair of tables" it become
clear that alter- algorithm made it harder to provide a better and
more consistent ALTER TABLE FORCE and REPAIR TABLE and it would be
better to remove it.
- ALTER_ALGORITHM should be substituted when there is no mention of
algorithm in alter statement.
- Introduced algorithm(thd) in Alter_info. It returns the
user requested algorithm. If user doesn't specify algorithm explicitly then
it returns alter_algorithm variable.
- changed algorithm() to get_algorithm(thd) to return algorithm name for
displaying the error.
- set_requested_algorithm(algo_value) to avoid direct assignment on
requested_algorithm variable.
- Avoid direct access of requested_algorithm to encapsulate
requested_algorithm variable
Remove the separate test innodb.alter_instant, because
it can be easily mistaken for innodb.instant_alter, which
in turn is covering various instant ALTER TABLE operations.
The table option page_compression_level is something that only
affects future writes, not actually the data format. Therefore,
we can allow instant changes of this option.
Similarly, the table option page_compressed can be set on a
previously uncompressed table without rebuilding the table,
because an uncompressed page would be considered valid when
reading a page_compressed table.
Removing the page_compressed option will continue to require
the table to be rebuilt.
ha_innobase_inplace_ctx::page_compression_level: The requested
page_compression_level at the start of ALTER TABLE, or 0 if
page_compressed=OFF.
alter_options_need_rebuild(): Renamed from
create_option_need_rebuild(). Allow page_compression_level and
page_compressed to be changed as above, without rebuilding the table.
ha_innobase::check_if_supported_inplace_alter(): Allow ALGORITHM=INSTANT
for ALTER_OPTIONS if the table is not to be rebuilt. If rebuild is
needed, set ha_alter_info->unsupported_reason.
innobase_page_compression_try(): Update SYS_TABLES.TYPE according
to the table flags, for an instant change of page_compression_level
or page_compressed.
commit_cache_norebuild(): Adjust dict_table_t::flags, fil_space_t::flags
and (if needed) FSP_SPACE_FLAGS if page_compression_level was specified.
Introduced new alter algorithm type called NOCOPY & INSTANT for
inplace alter operation.
NOCOPY - Algorithm refuses any alter operation that would
rebuild the clustered index. It is a subset of INPLACE algorithm.
INSTANT - Algorithm allow any alter operation that would
modify only meta data. It is a subset of NOCOPY algorithm.
Introduce new variable called alter_algorithm. The values are
DEFAULT(0), COPY(1), INPLACE(2), NOCOPY(3), INSTANT(4)
Message to deprecate old_alter_table variable and make it alias
for alter_algorithm variable.
alter_algorithm variable for slave is always set to default.
