The new shard copy code that was created for shard splits has some
advantages over the old shard copy code. The old code was using
worker_append_table_to_shard, which wrote to disk twice. And it also
didn't use binary copy when that was possible. Both of these issues
were fixed in the new copy code. This PR starts using this new copy
logic also for shard moves, not just for shard splits.
On my local machine I created a single shard table like this.
```sql
set citus.shard_count = 1;
create table t(id bigint, a bigint);
select create_distributed_table('t', 'id');
INSERT into t(id, a) SELECT i, i from generate_series(1, 100000000) i;
```
I then turned `fsync` off to make sure I wasn't bottlenecked by disk.
Finally I moved this shard between nodes with `citus_move_shard_placement`
with `block_writes`.
Before this PR a move took ~127s, after this PR it took only ~38s. So for this
small test this resulted in spending ~70% less time.
And I also tried the same test for a table that contained large strings:
```sql
set citus.shard_count = 1;
create table t(id bigint, a bigint, content text);
select create_distributed_table('t', 'id');
INSERT into t(id, a, content) SELECT i, i, 'aunethautnehoautnheaotnuhetnohueoutnehotnuhetncouhaeohuaeochgrhgd.athbetndairgexdbuhaobulrhdbaetoausnetohuracehousncaoehuesousnaceohuenacouhancoexdaseohusnaetobuetnoduhasneouhaceohusnaoetcuhmsnaetohuacoeuhebtokteaoshetouhsanetouhaoug.lcuahesonuthaseauhcoerhuaoecuh.lg;rcydabsnetabuesabhenth' from generate_series(1, 20000000) i;
```
While testing 5670dffd33, I realized
that we have a missing RecordNonDistTableAccessesForTask() for
local utility commands.
Although we don't have to record the relation access for local
only cases, we really want to keep the behaviour for scale-out
be the same with single node on all aspects. We wouldn't want
any single node complex transaction to work on single machine,
but not on multi node cluster. Hence, we apply the same restrictions.
For example, on a distributed cluster, the following errors, and
after this commit this errors locally as well
```SQL
CREATE TABLE ref(a int primary key);
INSERT INTO ref VALUES (1);
CREATE TABLE dist(a int REFERENCES ref(a));
SELECT create_reference_table('ref');
SELECT create_distributed_table('dist', 'a');
BEGIN;
SELECT * FROM dist;
TRUNCATE ref CASCADE;
ERROR: cannot execute DDL on table "ref" because there was a parallel SELECT access to distributed table "dist" in the same transaction
HINT: Try re-running the transaction with "SET LOCAL citus.multi_shard_modify_mode TO 'sequential';"
COMMIT;
```
We also add the comprehensive test suite and run the same locally.
Code snippet in Makefile was blocking Citus build when USE_PGXS flag was set. This was included for port to FSPG but is not needed for Citus engine and can be safely removed.
Reported bug #5803 shows that we are currently not sending the IN clause to our planner for columnar. This PR fixes it by checking for ScalarArrayOpExpr in ExtractPushdownClause so that we do not skip it. Also added a test case for this new addition.
It turns out that create_distributed_table
and citus_move/copy_shard_placement does not
work well concurrently.
To fix that, we need to acquire a lock, which
sounds like a good use of colocation lock.
However, the current usage of colocation lock is
limited to higher level UDFs like rebalance_table_shards
etc. Those usage of lock is still useful, but
we cannot acquire the same lock on citus_move_shard_placement
etc. because the coordinator connects to itself to acquire
the lock. Hence, the high level UDF blocks itself.
To fix that, we use one more colocation lock, with the placements
are the main objects to consider.
Before this commit, we required multiple copies of the
same stringInfo if we needed to append/prepend data to
the stringInfo. Now, we optionally get prefix/postfix.
For large string operations, this can save up to %10
memory.
Previously, CreateFixPartitionShardIndexNames() created all
the relevant query strings for all the shards, and executed
the large query string. And, in terms of the memory consumption,
this huge command (and its ExprContext generated while running
the command) is the main bottleneck/
With this change, we are reducing the total amount of memory
usage to almost 1/shard_count.
On my local machine, a distributed partitioned table with 120 partitions,
each 32 shards, the total memory consumption reduced from ~3GB
to ~0.1GB. And, the total execution time increased from ~28 seconds
to ~30 seconds. This seems like a good trade-off.
We used to only check whether the PID is valid
or not. However, Postgres does not necessarily
set the PID of the backend to 0 when it exists.
Instead, we need to be able to check it from procArray.
IsBackendPid() is what pg_stat_activity also relies
on for a similar purpose.
We have been testing with the 'latest' version of libpq when the CI
images were build. This has the downside that rebuilding the images
often break our tests due to different errors returned from libpq.
With this change we will actually test with a stable version of libpq
that is based on the postgres minor version that we test against.
This will make it easier to maintain postgres images over time, as well
as running all tests locally, where we change libpq in sync with the
postgres server version.
Historically we have been testing with the 'latest' version of libpq
when the CI images were build. This has the downside that rebuilding the
images often break our tests due to different errors returned from
libpq.
With this change we will actually test with a stable version of libpq
that is based on the postgres minor version that we test against.
This will make it easier to maintain postgres images over time, as well
as running _all_ tests locally, where we change libpq in sync with the
postgres server version.
use RecurseObjectDependencies api to find if an object is citus depended
make vanilla tests runnable to see if citus_depended function is working correctly
citus_locks combines the pg_locks views from all nodes and adds
global_pid, nodeid, and relation_name. The columns of citus_locks don't
change based on the Postgres version, however the pg_locks's columns do.
Postgres 14 added one more column to pg_locks (waitstart timestamptz).
citus_locks has the most expansive column set, including the newly added
column. If citus_locks is queried in a Postgres version where pg_locks
doesn't have some columns, the values for those columns in citus_locks
will be NULL
DESCRIPTION:
This PR extends support for Partitioned and Columnar tables in blocking 'citus_split_shard_by_split_points' workflow.
Columnar Support : No special handling required. Just removing checks that fails split for columnar table and adding test coverage.
Partitioned Table Support :
Skip copying of parent table as they are empty, The partitions contain data and are treated as co-located shards that will be copied separately.
Attach partitions to parent on destination after inserting new shard metadata and before creating foreign key constraints.
MISC:
Fix Bug #4949 where Blocking shard moves fails if there is a foreign key between partitioned distributed tables (from child to parent).
TEST:
Added new test 'citus_split_shards_columnar_partitioned' for splitting 'partitioned' and 'columnar + partitioned' table.
Added new test 'shard_move_constraints_blocking' to add coverage for shard move bug fix.
Updated test 'citus_split_shard_by_split_points_negative' to allow columnar and partitioned table.
For working on initial changes to postgres beta versions make the version check in `./configure` default, but optional.
Normal users will still get the postgres version check error when building on other postgres versions, however, advanced users can use this flag to force configure to pass and find the compilation errors Citus would run into.
Use of the flag is not advised for users not understanding what this does.
* Remove if conditions with PG_VERSION_NUM < 13
* Remove server_above_twelve(&eleven) checks from tests
* Fix tests
* Remove pg12 and pg11 alternative test output files
* Remove pg12 specific normalization rules
* Some more if conditions in the code
* Change RemoteCollationIdExpression and some pg12/pg13 comments
* Remove some more normalization rules
Onder Kalaci
Jelte Fennema
Naisila Puka
Onur Tirtir
aykut-bozkurt
Marco Slot
Marco Slot
Ying Xu
Ahmet Gedemenli
Hanefi Onaldi
Nils Dijk
Nitish Upreti