Added a new UDF, mark_tables_colocated(), to colocate tables with the same
configuration (shard count, shard replication count and distribution column type).
This forces prepared statements to be re-planned after changes of the
placement metadata. There's some locking issues remaining, but that's a
a separate task.
Also add regression tests verifying that invalidations take effect on
prepared statements.
This change adds the required infrastructure about metadata snapshot from MX
codebase into Citus, mainly metadata_sync.c file and master_metadata_snapshot UDF.
So far placements were assigned an Oid, but that was just used to track
insertion order. It also did so incompletely, as it was not preserved
across changes of the shard state. The behaviour around oid wraparound
was also not entirely as intended.
The newly introduced, explicitly assigned, IDs are preserved across
shard-state changes.
The prime goal of this change is not to improve ordering of task
assignment policies, but to make it easier to reference shards. The
newly introduced UpdateShardPlacementState() makes use of that, and so
will the in-progress connection and transaction management changes.
Related to #786
This change adds the `pg_dist_node` table that contains the information
about the workers in the cluster, replacing the previously used
`pg_worker_list.conf` file (or the one specified with `citus.worker_list_file`).
Upon update, `pg_worker_list.conf` file is read and `pg_dist_node` table is
populated with the file's content. After that, `pg_worker_list.conf` file
is renamed to `pg_worker_list.conf.obsolete`
For adding and removing nodes, the change also includes two new UDFs:
`master_add_node` and `master_remove_node`, which require superuser
permissions.
'citus.worker_list_file' guc is kept for update purposes but not used after the
update is finished.
Fixescitusdata/citus#714
On `InsertShardRow`, we previously called `CommandCounterIncrement()` before
`CitusInvalidateRelcacheByRelid(relationId);`. This might prevent to skip
invalidation of the distributed table in the next access within the same session.
That's important because ownership of relations implies special
privileges. Without this change, a distributed table can be accessible
by a table's owner, but a shard created by another user might not.
\stage so far directly inserted into pg_dist_shard and
pg_dist_shard_placement. That makes it hard to do effective permission
checks. Thus move the inserts into two C functions.
These two new functions aren't the nicest abstraction. But as we are
planning to obsolete \stage, it doesn't seem worthwhile to refactor the
client-side code of \stage to allow the use of
master_create_empty_shard() et al.
Previously several commands, amongst them commands like
master_create_distributed_table(), were allowed for everyone. That's not
good: Even though citus currently requires superuser permissions, we
shouldn't allow non-superusers to perform actions as sensitive as making
a table distributed.
There's no checks on the worker_* functions, as these usually just punt
the action to underlying postgres functionality, which then perform the
necessary checks.
This commit adds a fast shard pruning path for INSERTs on
hash-partitioned tables. The rationale behind this change is
that if there exists a sorted shard interval array, a single
index lookup on the array allows us to find the corresponding
shard interval. As mentioned above, we need a sorted
(wrt shardminvalue) shard interval array. Thus, this commit
updates shardIntervalArray to sortedShardIntervalArray in the
metadata cache. Then uses the low-level API that is defined in
multi_copy to handle the fast shard pruning.
The performance impact of this change is more apparent as more
shards exist for a distributed table. Previous implementation
was relying on linear search through the shard intervals. However,
this commit relies on constant lookup time on shard interval
array. Thus, the shard pruning becomes less dependent on the
shard count.
After this change, shards and associated metadata are automatically
dropped when running DROP TABLE on a distributed table, which fixes#230.
It also adds schema support for master_apply_delete_command, which
fixes#73.
Dropping the shards happens in the master_drop_all_shards UDF, which is
called from the SQL_DROP trigger. Inside the trigger, the table is no
longer visible and calling master_apply_delete_command directly wouldn't
work and oid <-> name mappings are not available. The
master_drop_all_shards function therefore takes the relation id, schema
name, and table name as parameters, which can be obtained from
pg_event_trigger_dropped_objects() in the SQL_DROP trigger. If the user
calls master_drop_all_shards while the table still exists, the schema
name and table name are ignored.
Author: Marco Slot
Reviewed-By: Andres Freund
Metin Doslu
Andres Freund
Brian Cloutier
Eren Basak
Robin Thomas
Murat Tuncer
Onder Kalaci
Brian Cloutier
Jason Petersen
Marco Slot