Propagate vacuum to compressed relation when running on chunk

.unreleased/fix_vacuum_compressed_chunk

@@ -0,0 +1,2 @@
+Fixes: #10286 Propagate VACUUM on a chunk to the compressed relation when running on chunk directly
+Thanks: @h0rn3t for reporting a problem with VACUUM not propagating to the compressed relation

src/process_utility.c

@@ -1282,6 +1282,23 @@ process_vacuum(ProcessUtilityArgs *args)
 					ctx.ht_vacuum_rel = vacuum_rel;
 					foreach_chunk(ht, add_chunk_to_vacuum, &ctx, false);
 				}
+				else
+				{
+					/* VACUUM targets a chunk directly. */
+					Chunk *chunk = ts_chunk_get_by_relid(table_relid, false);
+					if (chunk && ts_chunk_is_compressed(chunk))
+					{
+						Oid compressed_relid = ts_relation_get_compressed_relid(chunk->fd.relid);
+						/* Compressed chunk might be missing due to concurrent operations */
+						if (OidIsValid(compressed_relid))
+						{
+							ctx.chunk_rels =
+								lappend(ctx.chunk_rels,
+										makeVacuumRelation(NULL, compressed_relid, NIL));
+						}
+					}
+					register_chunk_for_rebuild_if_needed(table_relid, &ctx);
+				}
 			}
 			vacuum_rels = lappend(vacuum_rels, vacuum_rel);
 		}

tsl/test/expected/vacuum.out

@@ -300,3 +300,35 @@ DROP FUNCTION cagg_analyze_count_analyzed(name);
 DROP MATERIALIZED VIEW cagg_analyze_view;
 NOTICE:  drop cascades to table _timescaledb_internal._hyper_6_9_chunk
 DROP TABLE cagg_analyze_src;
+-- VACUUM FULL on an individual chunk should also rewrite the underlying compressed relation
+-- VACUUM FULL assigns a new relfilenode, so we use that as a proxy for the
+-- compressed relation actually being processed.
+CREATE TABLE vacuum_chunk_test(time timestamptz NOT NULL, device int, value float);
+SELECT create_hypertable('vacuum_chunk_test', 'time', chunk_time_interval => interval '1 day');
+       create_hypertable        
+--------------------------------
+ (7,public,vacuum_chunk_test,t)
+
+INSERT INTO vacuum_chunk_test
+SELECT '2024-01-01'::timestamptz + (i || ' minute')::interval, i % 4, i::float
+FROM generate_series(0, 5000) i;
+ALTER TABLE vacuum_chunk_test SET (timescaledb.compress, timescaledb.compress_segmentby = 'device');
+SELECT count(compress_chunk(ch)) FROM show_chunks('vacuum_chunk_test') ch;
+ count 
+-------
+     4
+
+SELECT ch AS chunk FROM show_chunks('vacuum_chunk_test') ch ORDER BY ch LIMIT 1 \gset
+SELECT cs.compress_relid::oid AS compressed_relid
+FROM _timescaledb_catalog.compression_settings cs
+WHERE cs.relid = :'chunk'::regclass \gset
+SELECT relfilenode AS compressed_relfilenode_before
+FROM pg_class WHERE oid = :compressed_relid \gset
+VACUUM FULL :chunk;
+SELECT relfilenode <> :compressed_relfilenode_before AS compressed_rel_rewritten
+FROM pg_class WHERE oid = :compressed_relid;
+ compressed_rel_rewritten 
+--------------------------
+ t
+
+DROP TABLE vacuum_chunk_test;

tsl/test/sql/vacuum.sql

@@ -230,3 +230,32 @@ WHERE parent.hypertable_id = (SELECT mat_hypertable_id
 DROP FUNCTION cagg_analyze_count_analyzed(name);
 DROP MATERIALIZED VIEW cagg_analyze_view;
 DROP TABLE cagg_analyze_src;
+
+-- VACUUM FULL on an individual chunk should also rewrite the underlying compressed relation
+-- VACUUM FULL assigns a new relfilenode, so we use that as a proxy for the
+-- compressed relation actually being processed.
+CREATE TABLE vacuum_chunk_test(time timestamptz NOT NULL, device int, value float);
+SELECT create_hypertable('vacuum_chunk_test', 'time', chunk_time_interval => interval '1 day');
+
+INSERT INTO vacuum_chunk_test
+SELECT '2024-01-01'::timestamptz + (i || ' minute')::interval, i % 4, i::float
+FROM generate_series(0, 5000) i;
+
+ALTER TABLE vacuum_chunk_test SET (timescaledb.compress, timescaledb.compress_segmentby = 'device');
+SELECT count(compress_chunk(ch)) FROM show_chunks('vacuum_chunk_test') ch;
+
+SELECT ch AS chunk FROM show_chunks('vacuum_chunk_test') ch ORDER BY ch LIMIT 1 \gset
+
+SELECT cs.compress_relid::oid AS compressed_relid
+FROM _timescaledb_catalog.compression_settings cs
+WHERE cs.relid = :'chunk'::regclass \gset
+
+SELECT relfilenode AS compressed_relfilenode_before
+FROM pg_class WHERE oid = :compressed_relid \gset
+
+VACUUM FULL :chunk;
+
+SELECT relfilenode <> :compressed_relfilenode_before AS compressed_rel_rewritten
+FROM pg_class WHERE oid = :compressed_relid;
+
+DROP TABLE vacuum_chunk_test;