While ALTER thread tries to notify SELECT thread about lock conflict
it accesses its TABLE object (THD::notify_shared_lock()) and lock data
(mysql_lock_abort_for_thread()). As part of accessing lock data it
calls ha_partition::store_lock() which iterates over all partitions
and does their store_lock().
The problem is SELECT opened 2 read partitions, but
ha_partition::store_lock() tries to access all partitions as indicated
in m_tot_parts which is 4. So the last 2 partitions m_file[2] and
m_file[3] are uninitialized and store_lock() accesses uninitialized
data.
The code in ha_partition::store_lock() does this wrong handling to use
all partitions specifically for the case of
mysql_lock_abort_for_thread(), this is conducted with comment:
/*
This can be called from get_lock_data() in mysql_lock_abort_for_thread(),
even when thd != table->in_use. In that case don't use partition pruning,
but use all partitions instead to avoid using another threads structures.
*/
if (thd != table->in_use)
{
for (i= 0; i < m_tot_parts; i++)
to= m_file[i]->store_lock(thd, to, lock_type);
}
The explanation is "to avoid using another threads structures" does
not really explain why this change was needed.
The change was originally introduced by:
commit 9b7cccaf319
Author: Mattias Jonsson <mattias.jonsson@oracle.com>
Date: Wed May 30 00:14:39 2012 +0200
WL#4443:
final code change for dlenevs review.
- Don't use pruning in lock_count().
- Don't use pruning in store_lock() if not owning thd.
- Renamed is_fields_used_in_trigger to
is_fields_updated_in_trigger() and check if they
may be updated.
- moved out mark_fields_used(TRG_EVENT_UPDATE)
from mark_columns_needed_for_update().
And reverted the changed call order. And call
mark_fields_used(TRG_EVENT_UPDATE) instead.
which also fails to explain the rationale of the change. The original
idea of WL#4443 is to reduce locks and this change does not happen to
serve this goal.
So reverting this change restores original behaviour of using only
partitions marked for use and fixes invalid access to uninitialized
data.
MDEV-22088 S3 partitioning support
All ALTER PARTITION commands should now work on S3 tables except
REBUILD PARTITION
TRUNCATE PARTITION
REORGANIZE PARTITION
In addition, PARTIONED S3 TABLES can also be replicated.
This is achived by storing the partition tables .frm and .par file on S3
for partitioned shared (S3) tables.
The discovery methods are enchanced by allowing engines that supports
discovery to also support of the partitioned tables .frm and .par file
Things in more detail
- The .frm and .par files of partitioned tables are stored in S3 and kept
in sync.
- Added hton callback create_partitioning_metadata to inform handler
that metadata for a partitoned file has changed
- Added back handler::discover_check_version() to be able to check if
a table's or a part table's definition has changed.
- Added handler::check_if_updates_are_ignored(). Needed for partitioning.
- Renamed rebind() -> rebind_psi(), as it was before.
- Changed CHF_xxx hadnler flags to an enum
- Changed some checks from using table->file->ht to use
table->file->partition_ht() to get discovery to work with partitioning.
- If TABLE_SHARE::init_from_binary_frm_image() fails, ensure that we
don't leave any .frm or .par files around.
- Fixed that writefrm() doesn't leave unusable .frm files around
- Appended extension to path for writefrm() to be able to reuse to function
for creating .par files.
- Added DBUG_PUSH("") to a a few functions that caused a lot of not
critical tracing.
