Support concurrent partition detach

[Andrey Borodin (x4m)]

Support ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY for distributed
partitioned tables.

PostgreSQL implements concurrent detach using two transactions, so shard
commands cannot run inside worker_apply_inter_shard_ddl_command(). This
change instead builds top-level nontransactional commands for each colocated
pair of parent and partition shards. The detached table remains available as
an independent distributed table and can be dropped separately.

DETACH PARTITION ... FINALIZE propagates a full concurrent detach to the
workers. This lets it finish an operation canceled after PostgreSQL committed
the coordinator's pending-detach state but before Citus started worker DDL.

The tests cover a normal detach and that interruption window, including the
catalog state on both workers before and after FINALIZE.

One design question remains: nontransactional DDL can fail on only some
placements after the coordinator has completed. The patch currently uses the
same partial-failure warning mechanism as other concurrent Citus DDL. Should
we also make FINALIZE an idempotent placement-reconciliation operation before
merging this?

Fixes #5264

[Copilot]

Pull request overview

Adds support for PostgreSQL 14’s ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY (and recovery via ... FINALIZE) for distributed partitioned tables in Citus. This fits into Citus’ DDL propagation layer by introducing a non-transactional worker execution path for this specific DDL, since PostgreSQL implements concurrent detach using multiple transactions.

Changes:

• Implement distributed concurrent partition detach by generating top-level, non-transactional per-(parent shard, partition shard) worker commands instead of using worker_apply_inter_shard_ddl_command().
• Treat DETACH PARTITION ... FINALIZE as a mechanism to run the full concurrent detach on workers (to complete operations interrupted after coordinator pending-detach state was committed).
• Add regression + isolation coverage for successful detach and the interruption/FINALIZE recovery window, and wire tests into schedules.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/backend/distributed/commands/table.c	Builds per-shard top-level DETACH PARTITION ... CONCURRENTLY tasks and routes FINALIZE through the same non-transactional worker path.
src/test/regress/sql/pg14.sql	Updates PG14 compatibility test to assert concurrent detach works on distributed partitioned tables.
src/test/regress/expected/pg14.out	Expected output updates for the new concurrent-detach behavior in pg14.sql.
src/test/regress/sql/detach_partition_concurrently.sql	New multi-node regression test validating detach behavior and post-detach usability of the detached table.
src/test/regress/expected/detach_partition_concurrently.out	Expected output for the new regression test.
src/test/regress/spec/isolation_detach_partition_concurrently.spec	New isolation test covering cancellation after coordinator pending-detach commit and recovery via FINALIZE.
src/test/regress/expected/isolation_detach_partition_concurrently.out	Expected isolation output for the new spec.
src/test/regress/multi_schedule	Schedules the new detach_partition_concurrently regression test.
src/test/regress/isolation_schedule	Schedules the new isolation test for concurrent detach recovery.

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[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

[codecov]

Codecov Report

❌ Patch coverage is 86.74699% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.72%. Comparing base (c5284e1) to head (5c69a92).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8802      +/-   ##
==========================================
- Coverage   88.74%   88.72%   -0.02%     
==========================================
  Files         289      289              
  Lines       64992    65069      +77     
  Branches     8200     8206       +6     
==========================================
+ Hits        57676    57735      +59     
- Misses       4950     4963      +13     
- Partials     2366     2371       +5     

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