Disable direct compress for tables with exclusion constraints

Direct compress writes data straight into compressed form without
per-row index checks, so it cannot enforce an exclusion constraint.
The fast path was only disabled for unique constraints, which meant
exclusion constraints were silently ignored. Disable direct compress
for both INSERT and COPY when the table has an exclusion constraint.

Author: svenklemm

.unreleased/fix_direct_compress_exclusion

@@ -0,0 +1 @@
+Fixes: #10281 Disable Direct Compress when the destination table has an exclusion constraint so the constraint is still enforced

src/copy.c

@@ -845,6 +845,12 @@ choose_copy_method(Hypertable *ht, CopyChunkState *ccstate, ResultRelInfo *resul
 					(errmsg("disabling direct compress because the destination table has unique "
 							"constraints")));
 		}
+		else if (ts_indexing_relation_has_exclusion_constraint(ccstate->rel))
+		{
+			ereport(WARNING,
+					(errmsg("disabling direct compress because the destination table has exclusion "
+							"constraints")));
+		}
 		else if (resultRelInfo->ri_TrigDesc && resultRelInfo->ri_TrigDesc->numtriggers > 1)
 		{
 			ereport(WARNING,

src/indexing.c

@@ -337,6 +337,40 @@ ts_indexing_relation_has_primary_or_unique_index(Relation htrel)
 	return result;
 }
 
+bool TSDLLEXPORT
+ts_indexing_relation_has_exclusion_constraint(Relation htrel)
+{
+	List *indexoidlist = RelationGetIndexList(htrel);
+	ListCell *lc;
+	bool result = false;
+
+	foreach (lc, indexoidlist)
+	{
+		Oid indexoid = lfirst_oid(lc);
+		HeapTuple index_tuple;
+		Form_pg_index index;
+
+		index_tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
+		if (!HeapTupleIsValid(index_tuple)) /* should not happen */
+		{
+			elog(ERROR,
+				 "cache lookup failed for index %u in \"%s\" ",
+				 indexoid,
+				 RelationGetRelationName(htrel));
+		}
+		index = (Form_pg_index) GETSTRUCT(index_tuple);
+		result = index->indisexclusion;
+		ReleaseSysCache(index_tuple);
+		if (result)
+		{
+			break;
+		}
+	}
+
+	list_free(indexoidlist);
+	return result;
+}
+
 /*
  * Collect the heap attribute numbers covered by any valid unique index
  * (PRIMARY KEY included) on the relation. Returns a Bitmapset of raw attribute

src/indexing.h

@@ -24,6 +24,7 @@ extern TSDLLEXPORT Oid ts_indexing_find_clustered_index(Oid table_relid);
 extern void ts_indexing_mark_as_valid(Oid index_id);
 extern bool ts_indexing_mark_as_invalid(Oid index_id);
 extern bool TSDLLEXPORT ts_indexing_relation_has_primary_or_unique_index(Relation htrel);
+extern bool TSDLLEXPORT ts_indexing_relation_has_exclusion_constraint(Relation htrel);
 extern TSDLLEXPORT Bitmapset *ts_indexing_relation_get_unique_columns(Relation rel);
 extern TSDLLEXPORT bool ts_indexing_compare(Oid index1, Oid index2);
 extern TSDLLEXPORT Datum ts_index_matches(PG_FUNCTION_ARGS);

src/nodes/modify_hypertable.c

@@ -61,6 +61,14 @@ should_use_direct_compress(ModifyHypertableState *state)
 		return false;
 	}
 
+	if (ts_indexing_relation_has_exclusion_constraint(state->ctr->root_rel))
+	{
+		ereport(WARNING,
+				(errmsg("disabling direct compress because the destination table has exclusion "
+						"constraints")));
+		return false;
+	}
+
 	Plan *subplan = mtstate->ps.plan->lefttree;
 	if (subplan->plan_rows < 10)
 	{

tsl/test/expected/direct_compress_insert.out

@@ -932,3 +932,32 @@ SELECT count(*), min(value), max(value) FROM metrics_view;
 RESET timescaledb.enable_direct_compress_insert;
 DROP VIEW metrics_view_pos;
 DROP TABLE metrics_view;
+-- Direct compress must be disabled when the table has an exclusion constraint
+CREATE TABLE dc_excl(time timestamptz NOT NULL, device text NOT NULL, value float,
+    EXCLUDE USING btree (time WITH =, device WITH =))
+    WITH (tsdb.hypertable, tsdb.partition_column='time');
+ALTER TABLE dc_excl SET (timescaledb.compress, timescaledb.compress_segmentby='device');
+NOTICE:  updated compression settings will only apply to future compressions
+SET timescaledb.enable_direct_compress_insert = true;
+-- insert warns, disables direct compress and falls back to a normal insert
+INSERT INTO dc_excl SELECT '2025-01-01'::timestamptz + (i || ' minute')::interval, 'd1', i::float FROM generate_series(1,100) i;
+WARNING:  disabling direct compress because the destination table has exclusion constraints
+-- chunk stays uncompressed since direct compress was disabled
+SELECT DISTINCT _timescaledb_functions.chunk_status_text(chunk) FROM show_chunks('dc_excl') chunk;
+ chunk_status_text 
+-------------------
+ {}
+
+-- exclusion constraint is still enforced
+\set ON_ERROR_STOP 0
+INSERT INTO dc_excl VALUES ('2025-01-01'::timestamptz + INTERVAL '1 minute', 'd1', 99);
+WARNING:  disabling direct compress because the destination table has exclusion constraints
+ERROR:  conflicting key value violates exclusion constraint "62_dc_excl_time_device_excl"
+\set ON_ERROR_STOP 1
+SELECT count(*) FROM dc_excl;
+ count 
+-------
+   100
+
+RESET timescaledb.enable_direct_compress_insert;
+DROP TABLE dc_excl;

tsl/test/sql/direct_compress_insert.sql

@@ -551,3 +551,21 @@ RESET timescaledb.enable_direct_compress_insert;
 DROP VIEW metrics_view_pos;
 DROP TABLE metrics_view;
 
+-- Direct compress must be disabled when the table has an exclusion constraint
+CREATE TABLE dc_excl(time timestamptz NOT NULL, device text NOT NULL, value float,
+    EXCLUDE USING btree (time WITH =, device WITH =))
+    WITH (tsdb.hypertable, tsdb.partition_column='time');
+ALTER TABLE dc_excl SET (timescaledb.compress, timescaledb.compress_segmentby='device');
+SET timescaledb.enable_direct_compress_insert = true;
+-- insert warns, disables direct compress and falls back to a normal insert
+INSERT INTO dc_excl SELECT '2025-01-01'::timestamptz + (i || ' minute')::interval, 'd1', i::float FROM generate_series(1,100) i;
+-- chunk stays uncompressed since direct compress was disabled
+SELECT DISTINCT _timescaledb_functions.chunk_status_text(chunk) FROM show_chunks('dc_excl') chunk;
+-- exclusion constraint is still enforced
+\set ON_ERROR_STOP 0
+INSERT INTO dc_excl VALUES ('2025-01-01'::timestamptz + INTERVAL '1 minute', 'd1', 99);
+\set ON_ERROR_STOP 1
+SELECT count(*) FROM dc_excl;
+RESET timescaledb.enable_direct_compress_insert;
+DROP TABLE dc_excl;
+