This pull request addresses Issue #7846, where specific MERGE queries on
non-distributed and distributed tables can result in crashes in certain
scenarios. The issue stems from the usage of `pg_class` catalog table,
and the `FilterShardsFromPgclass` function in Citus. This function goes
through the query's jointree to hide the shards. However, in PG17,
MERGE's join quals are in a separate structure called
`mergeJoinCondition`. Therefore FilterShardsFromPgclass was not
filtering correctly in a `MERGE` command that involves `pg_class`. To
fix the issue, we handle `mergeJoinCondition` separately in PG17.
Relevant PG commit:
0294df2f1f
**Non-Distributed Tables:**
A MERGE query involving a non-distributed table using
`pg_catalog.pg_class` as the source may execute successfully but needs
testing to ensure stability.
**Distributed Tables:**
Performing a MERGE on a distributed table using `pg_catalog.pg_class` as
the source raises an error:
`ERROR: MERGE INTO a distributed table from Postgres table is not yet
supported`
However, in some cases, this can lead to a server crash if the
unsupported operation is not properly handled.
This is the test output from the same test conducted prior to the code
changes being implemented.
```
-- Issue #7846: Test crash scenarios with MERGE on non-distributed and distributed tables
-- Step 1: Connect to a worker node to verify shard visibility
\c postgresql://postgres@localhost::worker_1_port/regression?application_name=psql
SET search_path TO pg17;
-- Step 2: Create and test a non-distributed table
CREATE TABLE non_dist_table_12345 (id INTEGER);
-- Test MERGE on the non-distributed table
MERGE INTO non_dist_table_12345 AS target_0
USING pg_catalog.pg_class AS ref_0
ON target_0.id = ref_0.relpages
WHEN NOT MATCHED THEN DO NOTHING;
SSL SYSCALL error: EOF detected
connection to server was lost
```
This is prep work for successful compilation with PG17
PG17added foreach_ptr, foreach_int and foreach_oid macros
Relevant PG commit
14dd0f27d7cd56ffae9ecdbe324965073d01a9ff
14dd0f27d7
We already have these macros, but they are different with the
PG17 ones because our macros take a DECLARED variable, whereas
the PG16 macros declare a locally-scoped loop variable themselves.
Hence I am renaming our macros to foreach_declared_
I am separating this into its own PR since it touches many files. The
main compilation PR is https://github.com/citusdata/citus/pull/7699
DESCRIPTION: Fix performance issue when using "\d tablename" on a server
with many tables
We introduce a filter to every query on pg_class to automatically remove
shards. This is useful to make sure \d and PgAdmin are not cluttered
with shards. However, the way we were introducing this filter was using
`securityQuals` which can have negative impact on query performance.
On clusters with 100k+ tables this could cause a simple "\d tablename"
command to take multiple seconds, because a skipped optimization by
Postgres causes a full table scan. This changes the code to introduce
this filter in the regular `quals` list instead of in `securityQuals`.
Which causes Postgres to use the intended optimization again.
For reference, this was initially reported as a Postgres issue by me:
https://www.postgresql.org/message-id/flat/4189982.1712785863%40sss.pgh.pa.us#b87421293b362d581ea8677e3bfea920
This change adds a script to programatically group all includes in a
specific order. The script was used as a one time invocation to group
and sort all includes throught our formatted code. The grouping is as
follows:
- System includes (eg. `#include<...>`)
- Postgres.h (eg. `#include "postgres.h"`)
- Toplevel imports from postgres, not contained in a directory (eg.
`#include "miscadmin.h"`)
- General postgres includes (eg . `#include "nodes/..."`)
- Toplevel citus includes, not contained in a directory (eg. `#include
"citus_verion.h"`)
- Columnar includes (eg. `#include "columnar/..."`)
- Distributed includes (eg. `#include "distributed/..."`)
Because it is quite hard to understand the difference between toplevel
citus includes and toplevel postgres includes it hardcodes the list of
toplevel citus includes. In the same manner it assumes anything not
prefixed with `columnar/` or `distributed/` as a postgres include.
The sorting/grouping is enforced by CI. Since we do so with our own
script there are not changes required in our uncrustify configuration.
The aim of hiding shards is to hide shards from client applications.
Certain bg workers (such as pg_cron or Citus maintanince daemon)
should be treated like client applications because users can run
queries from such bg workers. And, these bg workers should follow
the similar application_name checks as client backeends.
Certain other bg workers, such as logical replication or postgres'
parallel workers, should never hide shards. They are internal
operations.
Similarly the other backend types like the walsender or
checkpointer or autovacuum should never hide shards.
With this commit, rebalancer backends are identified by application_name = citus_rebalancer
and the regular internal backends are identified by application_name = citus_internal
- Add support for CRETE INDEX ... ON ONLY: Before that commit we were not sending "ONLY" option to the worker nodes at all. With this commit, "ONLY" parameter will be sent to the worker nodes if it is necessary. (#4938)
- Add support for ALTER INDEX ... ATTACH PARTITION: Attach child_index to parent_index by creating same inheritance on shard level in addition to table level. (#4980)
Previously this was usually done after argument parsing. This can cause
SEGFAULTs if the number or type of arguments changes in a new version.
By checking that Citus version is correct before doing any argument
parsing we protect against these types of issues. Issues like this have
occurred in pg_auto_failover, so it's not just a theoretical issue.
The main reason why these calls were not at the top of functions is
really just historical. It was because in the past we didn't allow
statements before declarations. Thus having this check before the
argument parsing would have only been possible if we first declared all
variables.
In addition to moving existing CheckCitusVersion calls it also adds
these calls to rebalancer related functions (they were missing there).
#3866 removed the shard ID hash in metadata_cache.c to simplify cache management,
but we observed a significant performance regression that was being masked by the
performance improvement provided by #3654 in our benchmarks, but #3654 only
applies to specific workloads.
This PR brings back the shard ID cache as it existed before #3866 with some extra
measures to handle invalidation. When we load a table entry, we overwrite
ShardIdCacheEntry->tableEntry pointers for all the shards in that table, though
it's possible that the table no longer contains the old shard ID or the table
entry is never reloaded, which would leave a dangling pointer once the table
entry is freed. To handle that case, we remove all shard ID cache entries that
point exactly to that table entry when a table is freed (at the end of the
transaction or any call to CitusTableCacheFlushInvalidatedEntries).
Co-authored-by: SaitTalhaNisanci <s.talhanisanci@gmail.com>
Co-authored-by: Marco Slot <marco.slot@gmail.com>
Co-authored-by: Jelte Fennema <github-tech@jeltef.nl>
This commit uses *_walker instead of *_mutator for performance reasons.
Given that we're only updating a functionId in the tree, the approach
seems fine.
This commit by default enables hiding shard names on MX workers
by simple replacing `pg_table_is_visible()` calls with
`citus_table_is_visible()` calls on the MX worker nodes. The latter
function filters out tables that are known to be shards.
The main motivation of this change is a better UX. The functionality
can be opted out via a GUC.
We also added two views, namely citus_shards_on_worker and
citus_shard_indexes_on_worker such that users can query
them to see the shards and their corresponding indexes.
We also added debug messages such that the filtered tables can
be interactively seen by setting the level to DEBUG1.
Add ability to understand whether a table is a
known shard on MX workers. Note that this is only useful
and applicable for hiding shards on MX worker nodes given
that we can have metadata only there.
Mehmet YILMAZ
Naisila Puka
Gürkan İndibay
Jelte Fennema-Nio
Nils Dijk
Marco Slot
Onder Kalaci
Teja Mupparti
Onur Tirtir
Philip Dubé
Burak Velioglu
Ahmet Gedemenli
Jelte Fennema
Marco Slot
Hadi Moshayedi
SaitTalhaNisanci
Onder Kalaci