Fix FK constraints for compressed chunks

.unreleased/pr_6797

@@ -0,0 +1 @@
+Fixes: #6797 Fix foreign key constraint handling on compressed hypertables

src/chunk.c

@@ -3222,58 +3222,6 @@ ts_chunk_recreate_all_constraints_for_dimension(Hypertable *ht, int32 dimension_
 	chunk_scan_ctx_destroy(&chunkctx);
 }
 
-/*
- * Drops all FK constraints on a given chunk.
- * Currently it is used only for chunks, which have been compressed and
- * contain no data.
- */
-void
-ts_chunk_drop_fks(const Chunk *const chunk)
-{
-	Relation rel;
-	List *fks;
-	ListCell *lc;
-
-	ASSERT_IS_VALID_CHUNK(chunk);
-
-	rel = table_open(chunk->table_id, AccessShareLock);
-	fks = copyObject(RelationGetFKeyList(rel));
-	table_close(rel, AccessShareLock);
-
-	foreach (lc, fks)
-	{
-		const ForeignKeyCacheInfo *const fk = lfirst_node(ForeignKeyCacheInfo, lc);
-		ts_chunk_constraint_delete_by_constraint_name(chunk->fd.id,
-													  get_constraint_name(fk->conoid),
-													  true,
-													  true);
-	}
-}
-
-/*
- * Recreates all FK constraints on a chunk by using the constraints on the parent hypertable
- * as a template. Currently it is used only during chunk decompression, since FK constraints
- * are dropped during compression.
- */
-void
-ts_chunk_create_fks(const Hypertable *ht, const Chunk *const chunk)
-{
-	Relation rel;
-	List *fks;
-	ListCell *lc;
-
-	ASSERT_IS_VALID_CHUNK(chunk);
-
-	rel = table_open(chunk->hypertable_relid, AccessShareLock);
-	fks = copyObject(RelationGetFKeyList(rel));
-	table_close(rel, AccessShareLock);
-	foreach (lc, fks)
-	{
-		ForeignKeyCacheInfo *fk = lfirst_node(ForeignKeyCacheInfo, lc);
-		ts_chunk_constraint_create_on_chunk(ht, chunk, fk->conoid);
-	}
-}
-
 /*
  * Chunk catalog updates are done in three steps.
  * This is achieved by following this sequence:

src/chunk.h

@@ -187,8 +187,6 @@ extern bool ts_chunk_exists_relid(Oid relid);
 extern TSDLLEXPORT int ts_chunk_num_of_chunks_created_after(const Chunk *chunk);
 extern TSDLLEXPORT bool ts_chunk_exists_with_compression(int32 hypertable_id);
 extern void ts_chunk_recreate_all_constraints_for_dimension(Hypertable *ht, int32 dimension_id);
-extern TSDLLEXPORT void ts_chunk_drop_fks(const Chunk *const chunk);
-extern TSDLLEXPORT void ts_chunk_create_fks(const Hypertable *ht, const Chunk *const chunk);
 extern int ts_chunk_delete_by_hypertable_id(int32 hypertable_id);
 extern int ts_chunk_delete_by_name(const char *schema, const char *table, DropBehavior behavior);
 extern bool ts_chunk_set_name(Chunk *chunk, const char *newname);

tsl/src/compression/api.c

@@ -457,11 +457,6 @@ compress_chunk_impl(Oid hypertable_relid, Oid chunk_relid)
 	before_size = ts_relation_size_impl(cxt.srcht_chunk->table_id);
 	cstat = compress_chunk(cxt.srcht_chunk->table_id, compress_ht_chunk->table_id, insert_options);
 
-	/* Drop all FK constraints on the uncompressed chunk. This is needed to allow
-	 * cascading deleted data in FK-referenced tables, while blocking deleting data
-	 * directly on the hypertable or chunks.
-	 */
-	ts_chunk_drop_fks(cxt.srcht_chunk);
 	after_size = ts_relation_size_impl(compress_ht_chunk->table_id);
 
 	if (new_compressed_chunk)
@@ -596,9 +591,6 @@ decompress_chunk_impl(Chunk *uncompressed_chunk, bool if_compressed)
 
 	decompress_chunk(compressed_chunk->table_id, uncompressed_chunk->table_id);
 
-	/* Recreate FK constraints, since they were dropped during compression. */
-	ts_chunk_create_fks(uncompressed_hypertable, uncompressed_chunk);
-
 	/* Delete the compressed chunk */
 	ts_compression_chunk_size_delete(uncompressed_chunk->fd.id);
 	ts_chunk_clear_compressed_chunk(uncompressed_chunk);
@@ -670,12 +662,6 @@ tsl_create_compressed_chunk(PG_FUNCTION_ARGS)
 	ts_chunk_constraints_create(cxt.compress_ht, compress_ht_chunk);
 	ts_trigger_create_all_on_chunk(compress_ht_chunk);
 
-	/* Drop all FK constraints on the uncompressed chunk. This is needed to allow
-	 * cascading deleted data in FK-referenced tables, while blocking deleting data
-	 * directly on the hypertable or chunks.
-	 */
-	ts_chunk_drop_fks(cxt.srcht_chunk);
-
 	/* Insert empty stats to compression_chunk_size */
 	compression_chunk_size_catalog_insert(cxt.srcht_chunk->fd.id,
 										  &uncompressed_size,

tsl/test/expected/compression.out

@@ -1054,9 +1054,10 @@ SELECT constraint_schema, constraint_name, table_schema, table_name, constraint_
 FROM information_schema.table_constraints
 WHERE table_name = :'CHUNK_NAME' AND constraint_type = 'FOREIGN KEY'
 ORDER BY constraint_name;
- constraint_schema | constraint_name | table_schema | table_name | constraint_type 
--------------------+-----------------+--------------+------------+-----------------
-(0 rows)
+   constraint_schema   |      constraint_name      |     table_schema      |     table_name     | constraint_type 
+-----------------------+---------------------------+-----------------------+--------------------+-----------------
+ _timescaledb_internal | 42_6_hyper_device_id_fkey | _timescaledb_internal | _hyper_18_42_chunk | FOREIGN KEY
+(1 row)
 
 -- Delete data from compressed chunk directly fails
 \set ON_ERROR_STOP 0
@@ -1094,7 +1095,7 @@ WHERE table_name = :'CHUNK_NAME' AND constraint_type = 'FOREIGN KEY'
 ORDER BY constraint_name;
    constraint_schema   |      constraint_name      |     table_schema      |     table_name     | constraint_type 
 -----------------------+---------------------------+-----------------------+--------------------+-----------------
- _timescaledb_internal | 42_8_hyper_device_id_fkey | _timescaledb_internal | _hyper_18_42_chunk | FOREIGN KEY
+ _timescaledb_internal | 42_6_hyper_device_id_fkey | _timescaledb_internal | _hyper_18_42_chunk | FOREIGN KEY
 (1 row)
 
 -- create hypertable with 2 chunks

tsl/test/expected/compression_fks.out

@@ -0,0 +1,46 @@
+-- This file and its contents are licensed under the Timescale License.
+-- Please see the included NOTICE for copyright information and
+-- LICENSE-TIMESCALE for a copy of the license.
+-- test	foreign key constraints with compression
+CREATE TABLE keys(time timestamptz unique);
+CREATE TABLE ht_with_fk(time timestamptz);
+SELECT create_hypertable('ht_with_fk','time');
+NOTICE:  adding not-null constraint to column "time"
+    create_hypertable    
+-------------------------
+ (1,public,ht_with_fk,t)
+(1 row)
+
+ALTER TABLE ht_with_fk ADD CONSTRAINT keys FOREIGN KEY (time) REFERENCES keys(time) ON DELETE CASCADE;
+ALTER TABLE ht_with_fk SET (timescaledb.compress,timescaledb.compress_segmentby='time');
+NOTICE:  default order by for hypertable "ht_with_fk" is set to ""
+-- no keys added yet so any insert into ht_with_fk should fail
+\set ON_ERROR_STOP 0
+INSERT INTO ht_with_fk SELECT '2000-01-01';
+ERROR:  insert or update on table "_hyper_1_1_chunk" violates foreign key constraint "1_1_keys"
+\set ON_ERROR_STOP 1
+-- create a key in the referenced table
+INSERT INTO keys SELECT '2000-01-01';
+-- now the insert should succeed
+INSERT INTO ht_with_fk SELECT '2000-01-01';
+SELECT compress_chunk(ch) FROM show_chunks('ht_with_fk') ch;
+             compress_chunk             
+----------------------------------------
+ _timescaledb_internal._hyper_1_2_chunk
+(1 row)
+
+-- insert should still succeed after compression
+INSERT INTO ht_with_fk SELECT '2000-01-01';
+-- inserting key not present in keys should fail
+\set ON_ERROR_STOP 0
+INSERT INTO ht_with_fk SELECT '2000-01-01 0:00:01';
+ERROR:  insert or update on table "_hyper_1_2_chunk" violates foreign key constraint "2_2_keys"
+\set ON_ERROR_STOP 1
+SELECT conrelid::regclass,conname,confrelid::regclass FROM pg_constraint WHERE contype = 'f' AND confrelid = 'keys'::regclass ORDER BY conrelid::regclass::text COLLATE "C",conname;
+                    conrelid                    | conname  | confrelid 
+------------------------------------------------+----------+-----------
+ _timescaledb_internal._hyper_1_2_chunk         | 2_2_keys | keys
+ _timescaledb_internal.compress_hyper_2_3_chunk | keys     | keys
+ ht_with_fk                                     | keys     | keys
+(3 rows)
+

tsl/test/sql/CMakeLists.txt

@@ -22,6 +22,7 @@ set(TEST_FILES
     compression_create_compressed_table.sql
     compression_conflicts.sql
     compression_defaults.sql
+    compression_fks.sql
     compression_insert.sql
     compression_policy.sql
     compression_qualpushdown.sql

tsl/test/sql/compression_fks.sql

@@ -0,0 +1,35 @@
+-- This file and its contents are licensed under the Timescale License.
+-- Please see the included NOTICE for copyright information and
+-- LICENSE-TIMESCALE for a copy of the license.
+
+-- test	foreign key constraints with compression
+CREATE TABLE keys(time timestamptz unique);
+CREATE TABLE ht_with_fk(time timestamptz);
+SELECT create_hypertable('ht_with_fk','time');
+
+ALTER TABLE ht_with_fk ADD CONSTRAINT keys FOREIGN KEY (time) REFERENCES keys(time) ON DELETE CASCADE;
+ALTER TABLE ht_with_fk SET (timescaledb.compress,timescaledb.compress_segmentby='time');
+
+-- no keys added yet so any insert into ht_with_fk should fail
+\set ON_ERROR_STOP 0
+INSERT INTO ht_with_fk SELECT '2000-01-01';
+\set ON_ERROR_STOP 1
+
+-- create a key in the referenced table
+INSERT INTO keys SELECT '2000-01-01';
+
+-- now the insert should succeed
+INSERT INTO ht_with_fk SELECT '2000-01-01';
+
+SELECT compress_chunk(ch) FROM show_chunks('ht_with_fk') ch;
+
+-- insert should still succeed after compression
+INSERT INTO ht_with_fk SELECT '2000-01-01';
+
+-- inserting key not present in keys should fail
+\set ON_ERROR_STOP 0
+INSERT INTO ht_with_fk SELECT '2000-01-01 0:00:01';
+\set ON_ERROR_STOP 1
+
+SELECT conrelid::regclass,conname,confrelid::regclass FROM pg_constraint WHERE contype = 'f' AND confrelid = 'keys'::regclass ORDER BY conrelid::regclass::text COLLATE "C",conname;
+