Sometimes the background daemon doesn't cleanup orphaned shards quickly
enough. It's useful to have a UDF to trigger this removal when needed.
We already had a UDF like this but it was only used during testing. This
exposes that UDF to users. As a safety measure it cannot be run in a
transaction, because that would cause the background daemon to stop
cleaning up shards while this transaction is running.
Without this change the rebalancer progress monitor gets the shard sizes
from the `shardlength` column in `pg_dist_placement`. This column needs to
be updated manually by calling `citus_update_table_statistics`.
However, `citus_update_table_statistics` could lead to distributed
deadlocks while database traffic is on-going (see #4752).
To work around this we don't use `shardlength` column anymore. Instead
for every rebalance we now fetch all shard sizes on the fly.
Two additional things this does are:
1. It adds tests for the rebalance progress function.
2. If a shard move cannot be done because a source or target node is
unreachable, then we error in stop the rebalance, instead of showing
a warning and continuing. When using the by_disk_size rebalance
strategy it's not safe to continue with other moves if a specific
move failed. It's possible that the failed move made space for the
next move, and because the failed move never happened this space now
does not exist.
3. Adds two new columns to the result of `get_rebalancer_progress` which
shows the size of the shard on the source and target node.
Fixes#4930
DESCRIPTION: Add support for ALTER DATABASE OWNER
This adds support for changing the database owner. It achieves this by marking the database as a distributed object. By marking the database as a distributed object it will look for its dependencies and order the user creation commands (enterprise only) before the alter of the database owner. This is mostly important when adding new nodes.
By having the database marked as a distributed object it can easily understand for which `ALTER DATABASE ... OWNER TO ...` commands to propagate by resolving the object address of the database and verifying it is a distributed object, and hence should propagate changes of owner ship to all workers.
Given the ownership of the database might have implications on subsequent commands in transactions we force sequential mode for transactions that have a `ALTER DATABASE ... OWNER TO ...` command in them. This will fail the transaction with meaningful help when the transaction already executed parallel statements.
By default the feature is turned off since roles are not automatically propagated, having it turned on would cause hard to understand errors for the user. It can be turned on by the user via setting the `citus.enable_alter_database_owner`.
Every move in the rebalancer algorithm results in an improvement in the
balance. However, even if the improvement in the balance was very small
the move was still chosen. This is especially problematic if the shard
itself is very big and the move will take a long time.
This changes the rebalancer algorithm to take the relative size of the
balance improvement into account when choosing moves. By default a move
will not be chosen if it improves the balance by less than half of the
size of the shard. An extra argument is added to the rebalancer
functions so that the user can decide to lower the default threshold if
the ignored move is wanted anyway.
* When moving a shard to a new node ensure there is enough space
* Add WairForMiliseconds time utility
* Add more tests and increase readability
* Remove the retry loop and use a single udf for disk stats
* Address review
* address review
Co-authored-by: Jelte Fennema <github-tech@jeltef.nl>
* Introduce 3 partitioned size udfs
* Add tests for new partition size udfs
* Fix type incompatibilities
* Convert UDFs into pure sql functions
* Fix function comment
Postgres keeps AFTER trigger state for each transaction, because we can have deferred AFTER triggers which will be fired at the end of a transaction. Postgres cleans up this state at the end of transaction.
Postgres processes ON COMMIT triggers after cleaning-up the AFTER trigger states. So if we fire any triggers in ON COMMIT, the AFTER trigger state won't be cleaned-up properly and the transaction state will be left in an inconsistent state, which might result in assertion failure.
So with this commit, we remove foreign keys between columnar metadata tables and enforce constraints between them manually when dropping columnar tables.
* Reimplement citus_update_table_statistics
* Update stats for the given table not colocation group
* Add tests for reimplemented citus_update_table_statistics
* Use coordinated transaction, merge with citus_shard_sizes functions
* Update the old master_update_table_statistics as well
* Sort results in citus_shards and give raw size
Sort results so that it is consistent and also similar to citus_tables.
Use raw size in the output so that doing operations on the size is
easier.
* Change column ordering
* Fix partition column index issue
We send column names to worker_hash/range_partition_table methods, and
in these methods we check the column name index from tuple descriptor.
Then this index is used to decide the bucket that the current row will
be sent for the repartition.
This becomes a problem when there are the same column names in the
tupleDescriptor. Then we can choose the wrong index. Hence the
partitioned data will be put to wrong workers. Then the result could
miss some data because workers might contain different range of data.
An example:
TupleDescriptor contains "trip_id", "car_id", "car_id" for one table.
It contains only "car_id" for the other table. And assuming that the
tables will be partitioned by car_id, it is not certain what should be
used for deciding the bucket number for the first table. Assuming value
2 goes to bucket 2 and value 3 goes to bucket 3, it is not certain which
bucket "1 2 3" (trip_id, car_id, car_id) row will go to.
As a solution we send the index of partition column in targetList
instead of the column name.
The old API is kept so that if workers upgrade work, it still works
(though it will have the same bug)
* Use the same method so that backporting is easier
With citus shard helper view, we can easily see:
- where each shard is, which node, which port
- what kind of table it belongs to
- its size
With such a view, we can see shards that have a size bigger than some
value, which could be useful. Also debugging can be easier in production
as well with this view.
Fetch shards in one go per node
The previous implementation was slow because it would do a lot of round
trips, one per shard to be exact. Hence it is improved so that we fetch
all the shard_name, shard-size pairs per node in one go.
Construct shards_names, sizes query on coordinator
* Replace master_add_node with citus_add_node
* Replace master_activate_node with citus_activate_node
* Replace master_add_inactive_node with citus_add_inactive_node
* Use master udfs in old scripts
* Replace master_add_secondary_node with citus_add_secondary_node
* Replace master_disable_node with citus_disable_node
* Replace master_drain_node with citus_drain_node
* Replace master_remove_node with citus_remove_node
* Replace master_set_node_property with citus_set_node_property
* Replace master_unmark_object_distributed with citus_unmark_object_distributed
* Replace master_update_node with citus_update_node
* Replace master_update_shard_statistics with citus_update_shard_statistics
* Replace master_update_table_statistics with citus_update_table_statistics
* Rename master_conninfo_cache_invalidate to citus_conninfo_cache_invalidate
Rename master_dist_local_group_cache_invalidate to citus_dist_local_group_cache_invalidate
* Replace master_copy_shard_placement with citus_copy_shard_placement
* Replace master_move_shard_placement with citus_move_shard_placement
* Rename master_dist_node_cache_invalidate to citus_dist_node_cache_invalidate
* Rename master_dist_object_cache_invalidate to citus_dist_object_cache_invalidate
* Rename master_dist_partition_cache_invalidate to citus_dist_partition_cache_invalidate
* Rename master_dist_placement_cache_invalidate to citus_dist_placement_cache_invalidate
* Rename master_dist_shard_cache_invalidate to citus_dist_shard_cache_invalidate
* Drop master_modify_multiple_shards
* Rename master_drop_all_shards to citus_drop_all_shards
* Drop master_create_distributed_table
* Drop master_create_worker_shards
* Revert old function definitions
* Add missing revoke statement for citus_disable_node
Jelte Fennema
SaitTalhaNisanci
Hanefi Onaldi
Nils Dijk
Ahmet Gedemenli
Onur Tirtir
Halil Ozan Akgul
Naisila Puka
Marco Slot
Jeff Davis