Allow DROP CONSTRAINT on compressed hypertables

Removing constraints is always safe so there is no reason to block it on
compressed hypertables. Adding constraints is still blocked for
compressed hypertables as verifying of constraints currently requires
decompressed hypertable.

.unreleased/pr_6754

@@ -0,0 +1 @@
+Implements: #6754 Allow DROP CONSTRAINT on compressed hypertables

src/process_utility.c

@@ -250,10 +250,11 @@ check_alter_table_allowed_on_ht_with_compression(Hypertable *ht, AlterTableStmt
 				/* this is passed down in `process_altertable_change_owner` */
 			case AT_SetTableSpace:
 				/* this is passed down in `process_altertable_set_tablespace_end` */
-			case AT_SetStatistics: /* should this be pushed down in some way? */
+			case AT_SetStatistics:	/* should this be pushed down in some way? */
-			case AT_AddColumn:	   /* this is passed down */
+			case AT_AddColumn:		/* this is passed down */
-			case AT_ColumnDefault: /* this is passed down */
+			case AT_ColumnDefault:	/* this is passed down */
-			case AT_DropColumn:	   /* this is passed down */
+			case AT_DropColumn:		/* this is passed down */
+			case AT_DropConstraint: /* this is passed down */
 #if PG14_GE
 			case AT_ReAddStatistics:
 			case AT_SetCompression:

tsl/test/expected/compression_errors-13.out

@@ -208,8 +208,10 @@ ALTER TABLE foo ADD CONSTRAINT chk CHECK(b > 0);
 ERROR:  operation not supported on hypertables that have compression enabled
 ALTER TABLE foo ADD CONSTRAINT chk UNIQUE(b);
 ERROR:  operation not supported on hypertables that have compression enabled
+--should succeed
+BEGIN;
 ALTER TABLE foo DROP CONSTRAINT chk_existing;
-ERROR:  operation not supported on hypertables that have compression enabled
+ROLLBACK;
 --note that the time column "a" should not be added to the end of the order by list again (should appear first)
 SELECT * FROM _timescaledb_catalog.compression_settings WHERE relid = 'foo'::regclass;
  relid | segmentby | orderby | orderby_desc | orderby_nullsfirst 

tsl/test/expected/compression_errors-14.out

@@ -208,8 +208,10 @@ ALTER TABLE foo ADD CONSTRAINT chk CHECK(b > 0);
 ERROR:  operation not supported on hypertables that have compression enabled
 ALTER TABLE foo ADD CONSTRAINT chk UNIQUE(b);
 ERROR:  operation not supported on hypertables that have compression enabled
+--should succeed
+BEGIN;
 ALTER TABLE foo DROP CONSTRAINT chk_existing;
-ERROR:  operation not supported on hypertables that have compression enabled
+ROLLBACK;
 --note that the time column "a" should not be added to the end of the order by list again (should appear first)
 SELECT * FROM _timescaledb_catalog.compression_settings WHERE relid = 'foo'::regclass;
  relid | segmentby | orderby | orderby_desc | orderby_nullsfirst 

tsl/test/expected/compression_errors-15.out

@@ -208,8 +208,10 @@ ALTER TABLE foo ADD CONSTRAINT chk CHECK(b > 0);
 ERROR:  operation not supported on hypertables that have compression enabled
 ALTER TABLE foo ADD CONSTRAINT chk UNIQUE(b);
 ERROR:  operation not supported on hypertables that have compression enabled
+--should succeed
+BEGIN;
 ALTER TABLE foo DROP CONSTRAINT chk_existing;
-ERROR:  operation not supported on hypertables that have compression enabled
+ROLLBACK;
 --note that the time column "a" should not be added to the end of the order by list again (should appear first)
 SELECT * FROM _timescaledb_catalog.compression_settings WHERE relid = 'foo'::regclass;
  relid | segmentby | orderby | orderby_desc | orderby_nullsfirst 

tsl/test/expected/compression_errors-16.out

@@ -208,8 +208,10 @@ ALTER TABLE foo ADD CONSTRAINT chk CHECK(b > 0);
 ERROR:  operation not supported on hypertables that have compression enabled
 ALTER TABLE foo ADD CONSTRAINT chk UNIQUE(b);
 ERROR:  operation not supported on hypertables that have compression enabled
+--should succeed
+BEGIN;
 ALTER TABLE foo DROP CONSTRAINT chk_existing;
-ERROR:  operation not supported on hypertables that have compression enabled
+ROLLBACK;
 --note that the time column "a" should not be added to the end of the order by list again (should appear first)
 SELECT * FROM _timescaledb_catalog.compression_settings WHERE relid = 'foo'::regclass;
  relid | segmentby | orderby | orderby_desc | orderby_nullsfirst 

tsl/test/sql/compression_errors.sql.in

@@ -112,7 +112,11 @@ ALTER TABLE foo ALTER COLUMN t SET NOT NULL;
 ALTER TABLE foo RESET (timescaledb.compress);
 ALTER TABLE foo ADD CONSTRAINT chk CHECK(b > 0);
 ALTER TABLE foo ADD CONSTRAINT chk UNIQUE(b);
+
+--should succeed
+BEGIN;
 ALTER TABLE foo DROP CONSTRAINT chk_existing;
+ROLLBACK;
 
 --note that the time column "a" should not be added to the end of the order by list again (should appear first)
 SELECT * FROM _timescaledb_catalog.compression_settings WHERE relid = 'foo'::regclass;