Fix unique index detection for compressed chunks

.unreleased/pr_6454

@@ -0,0 +1,2 @@
+Fixes: #6454 Fix unique expression indexes on compressed chunks
+Thanks: @aarondglover for reporting an issue with unique expression indexes on compressed chunks

src/indexing.c

@@ -274,10 +274,33 @@ indexing_create_and_verify_hypertable_indexes(const Hypertable *ht, bool create_
 bool TSDLLEXPORT
 ts_indexing_relation_has_primary_or_unique_index(Relation htrel)
 {
-	Bitmapset *key_attrs = RelationGetIndexAttrBitmap(htrel, INDEX_ATTR_BITMAP_KEY);
-	bool result = bms_num_members(key_attrs) > 0;
+	List *indexoidlist = RelationGetIndexList(htrel);
+	ListCell *lc;
+	bool result = false;
+
+	if (OidIsValid(htrel->rd_pkindex))
+		return true;
+
+	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->indisunique;
+		ReleaseSysCache(index_tuple);
+		if (result)
+			break;
+	}
 
-	bms_free(key_attrs);
+	list_free(indexoidlist);
 	return result;
 }
 

tsl/test/shared/expected/compress_unique_index.out

@@ -0,0 +1,33 @@
+-- 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 unique expression indexes
+CREATE TABLE compress_unique(offset_timestamp timestamptz not null, meter_id text, meter_channel_id text, timestamp timestamptz);
+SELECT table_name FROM create_hypertable('compress_unique','offset_timestamp');
+   table_name    
+ compress_unique
+(1 row)
+
+CREATE UNIQUE INDEX uniq_expr ON compress_unique USING btree (lower((meter_id)::text), meter_channel_id, offset_timestamp, "timestamp");
+ALTER TABLE compress_unique SET (timescaledb.compress,timescaledb.compress_segmentby='meter_id,meter_channel_id');
+WARNING:  column "timestamp" should be used for segmenting or ordering
+INSERT INTO compress_unique VALUES ('2000-01-01','m1','c1','2000-01-01');
+INSERT INTO compress_unique VALUES ('2000-01-01','m1','c2','2000-01-01');
+SELECT compress_chunk(show_chunks('compress_unique')) IS NOT NULL AS compress;
+ compress 
+ t
+(1 row)
+
+-- should fail
+\set ON_ERROR_STOP 0
+INSERT INTO compress_unique VALUES ('2000-01-01','m1','c2','2000-01-01');
+ERROR:  duplicate key value violates unique constraint "_hyper_X_X_chunk_uniq_expr"
+\set ON_ERROR_STOP 1
+SELECT * FROM compress_unique ORDER BY compress_unique;
+       offset_timestamp       | meter_id | meter_channel_id |          timestamp           
+------------------------------+----------+------------------+------------------------------
+ Sat Jan 01 00:00:00 2000 PST | m1       | c1               | Sat Jan 01 00:00:00 2000 PST
+ Sat Jan 01 00:00:00 2000 PST | m1       | c2               | Sat Jan 01 00:00:00 2000 PST
+(2 rows)
+
+DROP TABLE compress_unique;

tsl/test/shared/sql/CMakeLists.txt

@@ -2,6 +2,7 @@ set(TEST_FILES_SHARED
     cagg_compression.sql
     classify_relation.sql
     compat.sql
+    compress_unique_index.sql
     constify_timestamptz_op_interval.sql
     constraint_aware_append.sql
     constraint_exclusion_prepared.sql

tsl/test/shared/sql/compress_unique_index.sql

@@ -0,0 +1,26 @@
+-- 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 unique expression indexes
+
+CREATE TABLE compress_unique(offset_timestamp timestamptz not null, meter_id text, meter_channel_id text, timestamp timestamptz);
+SELECT table_name FROM create_hypertable('compress_unique','offset_timestamp');
+
+CREATE UNIQUE INDEX uniq_expr ON compress_unique USING btree (lower((meter_id)::text), meter_channel_id, offset_timestamp, "timestamp");
+ALTER TABLE compress_unique SET (timescaledb.compress,timescaledb.compress_segmentby='meter_id,meter_channel_id');
+
+INSERT INTO compress_unique VALUES ('2000-01-01','m1','c1','2000-01-01');
+INSERT INTO compress_unique VALUES ('2000-01-01','m1','c2','2000-01-01');
+
+SELECT compress_chunk(show_chunks('compress_unique')) IS NOT NULL AS compress;
+
+-- should fail
+\set ON_ERROR_STOP 0
+INSERT INTO compress_unique VALUES ('2000-01-01','m1','c2','2000-01-01');
+\set ON_ERROR_STOP 1
+
+SELECT * FROM compress_unique ORDER BY compress_unique;
+
+DROP TABLE compress_unique;
+