Prevent locking compressed tuples

Error out when we detect that a scan is trying to lock compressed
tuple. This does not block lock tuples on compressed hypertables
in general but only errors for queries where actual compressed
tuples would be returned. This will allow queries on compressed
hypertables where compressed tuples are filtered by other means
e.g. chunk exclusion or query constraints.
Not blocking this will produce a very misleading `Could not read
block 0` error.

.unreleased/pr_7046

@@ -0,0 +1 @@
+Fixes: #7046 Prevent locking compressed tuples

tsl/src/nodes/decompress_chunk/exec.c

@@ -82,6 +82,7 @@ decompress_chunk_state_create(CustomScan *cscan)
 		list_nth_int(settings, DCS_BatchSortedMerge);
 	chunk_state->decompress_context.enable_bulk_decompression =
 		list_nth_int(settings, DCS_EnableBulkDecompression);
+	chunk_state->has_row_marks = list_nth_int(settings, DCS_HasRowMarks);
 
 	Assert(IsA(cscan->custom_exprs, List));
 	Assert(list_length(cscan->custom_exprs) == 1);
@@ -429,6 +430,13 @@ decompress_chunk_exec_impl(DecompressChunkState *chunk_state, const BatchQueueFu
 		return NULL;
 	}
 
+	if (chunk_state->has_row_marks)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("locking compressed tuples is not supported")));
+	}
+
 	if (chunk_state->csstate.ss.ps.ps_ProjInfo)
 	{
 		ExprContext *econtext = chunk_state->csstate.ss.ps.ps_ExprContext;

tsl/src/nodes/decompress_chunk/exec.h

@@ -21,6 +21,7 @@ typedef struct DecompressChunkState
 	List *is_segmentby_column;
 	List *bulk_decompression_column;
 	List *custom_scan_tlist;
+	bool has_row_marks;
 
 	DecompressContext decompress_context;
 

tsl/src/nodes/decompress_chunk/planner.c

@@ -1304,6 +1304,7 @@ decompress_chunk_plan_create(PlannerInfo *root, RelOptInfo *rel, CustomPath *pat
 	lfirst_int(list_nth_cell(settings, DCS_Reverse)) = dcpath->reverse;
 	lfirst_int(list_nth_cell(settings, DCS_BatchSortedMerge)) = dcpath->batch_sorted_merge;
 	lfirst_int(list_nth_cell(settings, DCS_EnableBulkDecompression)) = enable_bulk_decompression;
+	lfirst_int(list_nth_cell(settings, DCS_HasRowMarks)) = root->parse->rowMarks != NIL;
 
 	/*
 	 * Vectorized quals must go into custom_exprs, because Postgres has to see

tsl/src/nodes/decompress_chunk/planner.h

@@ -14,6 +14,7 @@ typedef enum
 	DCS_Reverse = 2,
 	DCS_BatchSortedMerge = 3,
 	DCS_EnableBulkDecompression = 4,
+	DCS_HasRowMarks = 5,
 	DCS_Count
 } DecompressChunkSettingsIndex;
 

tsl/test/shared/expected/compression_dml.out

@@ -88,9 +88,9 @@ SELECT chunk_schema || '.' || chunk_name as "chunk_table"
        FROM timescaledb_information.chunks
        WHERE hypertable_name = 'mytab' ORDER BY range_start limit 1 \gset
 -- compress only the first chunk
-SELECT compress_chunk(:'chunk_table');
-              compress_chunk               
- _timescaledb_internal._hyper_X_X_chunk
+SELECT count(compress_chunk(:'chunk_table'));
+ count 
+     1
 (1 row)
 
 -- insert a row into first compressed chunk
@@ -127,11 +127,10 @@ FROM
 generate_series('1990-01-01'::timestamptz, '1990-01-10'::timestamptz, INTERVAL '1 day') AS g1(time),
 generate_series(1, 3, 1 ) AS g2(source_id),
 generate_series(1, 3, 1 ) AS g3(label);
-SELECT compress_chunk(c) FROM show_chunks('comp_seg_varchar') c;
-              compress_chunk               
- _timescaledb_internal._hyper_X_X_chunk
- _timescaledb_internal._hyper_X_X_chunk
-(2 rows)
+SELECT count(compress_chunk(c)) FROM show_chunks('comp_seg_varchar') c;
+ count 
+     2
+(1 row)
 
 -- all tuples should come from compressed chunks
 EXPLAIN (analyze,costs off, timing off, summary off) SELECT * FROM comp_seg_varchar;
@@ -170,3 +169,36 @@ QUERY PLAN
 (6 rows)
 
 DROP TABLE comp_seg_varchar;
+-- test row locks for compressed tuples are blocked
+CREATE TABLE row_locks(time timestamptz NOT NULL);
+SELECT table_name FROM create_hypertable('row_locks', 'time');
+ table_name 
+ row_locks
+(1 row)
+
+ALTER TABLE row_locks SET (timescaledb.compress);
+WARNING:  there was some uncertainty picking the default segment by for the hypertable: You do not have any indexes on columns that can be used for segment_by and thus we are not using segment_by for compression. Please make sure you are not missing any indexes
+NOTICE:  default segment by for hypertable "row_locks" is set to ""
+NOTICE:  default order by for hypertable "row_locks" is set to ""time" DESC"
+INSERT INTO row_locks VALUES('2021-01-01 00:00:00');
+SELECT count(compress_chunk(c)) FROM show_chunks('row_locks') c;
+ count 
+     1
+(1 row)
+
+-- should succeed cause no compressed tuples are returned
+SELECT FROM row_locks WHERE time < '2021-01-01 00:00:00' FOR UPDATE;
+(0 rows)
+
+-- should be blocked
+\set ON_ERROR_STOP 0
+SELECT FROM row_locks FOR UPDATE;
+ERROR:  locking compressed tuples is not supported
+SELECT FROM row_locks FOR NO KEY UPDATE;
+ERROR:  locking compressed tuples is not supported
+SELECT FROM row_locks FOR SHARE;
+ERROR:  locking compressed tuples is not supported
+SELECT FROM row_locks FOR KEY SHARE;
+ERROR:  locking compressed tuples is not supported
+\set ON_ERROR_STOP 1
+DROP TABLE row_locks;

tsl/test/shared/sql/compression_dml.sql

@@ -76,7 +76,7 @@ SELECT chunk_schema || '.' || chunk_name as "chunk_table"
        WHERE hypertable_name = 'mytab' ORDER BY range_start limit 1 \gset
 
 -- compress only the first chunk
-SELECT compress_chunk(:'chunk_table');
+SELECT count(compress_chunk(:'chunk_table'));
 
 -- insert a row into first compressed chunk
 INSERT INTO mytab SELECT '2022-10-07 05:30:10+05:30'::timestamp with time zone, 3, 3;
@@ -105,7 +105,7 @@ generate_series('1990-01-01'::timestamptz, '1990-01-10'::timestamptz, INTERVAL '
 generate_series(1, 3, 1 ) AS g2(source_id),
 generate_series(1, 3, 1 ) AS g3(label);
 
-SELECT compress_chunk(c) FROM show_chunks('comp_seg_varchar') c;
+SELECT count(compress_chunk(c)) FROM show_chunks('comp_seg_varchar') c;
 
 
 -- all tuples should come from compressed chunks
@@ -124,3 +124,24 @@ ON CONFLICT (source_id, label, time) DO UPDATE SET data = '{"update": true}';
 EXPLAIN (analyze,costs off, timing off, summary off) SELECT * FROM comp_seg_varchar;
 
 DROP TABLE comp_seg_varchar;
+
+-- test row locks for compressed tuples are blocked
+CREATE TABLE row_locks(time timestamptz NOT NULL);
+SELECT table_name FROM create_hypertable('row_locks', 'time');
+ALTER TABLE row_locks SET (timescaledb.compress);
+INSERT INTO row_locks VALUES('2021-01-01 00:00:00');
+SELECT count(compress_chunk(c)) FROM show_chunks('row_locks') c;
+
+-- should succeed cause no compressed tuples are returned
+SELECT FROM row_locks WHERE time < '2021-01-01 00:00:00' FOR UPDATE;
+-- should be blocked
+\set ON_ERROR_STOP 0
+SELECT FROM row_locks FOR UPDATE;
+SELECT FROM row_locks FOR NO KEY UPDATE;
+SELECT FROM row_locks FOR SHARE;
+SELECT FROM row_locks FOR KEY SHARE;
+\set ON_ERROR_STOP 1
+
+DROP TABLE row_locks;
+
+