Add support for ALTER COLUMN SET NOT NULL

Since `SET NOT NULL` will only do a full table scan of the table to
verify that there are no nulls, this should work without having to
modify any data in the table. However, it does not work for chunks
using the `heap` table access method if they are compressed since it
uses a normal table scan, so adding a check for this.

src/process_utility.c

@@ -281,6 +281,7 @@ check_alter_table_allowed_on_ht_with_compression(Hypertable *ht, AlterTableStmt
 			case AT_ReAddStatistics:
 			case AT_SetCompression:
 			case AT_DropNotNull:
+			case AT_SetNotNull:
 #if PG15_GE
 			case AT_SetAccessMethod:
 #endif
@@ -2563,11 +2564,50 @@ process_altertable_validate_constraint_end(Hypertable *ht, AlterTableCmd *cmd)
 	foreach_chunk(ht, validate_hypertable_constraint, cmd);
 }
 
+/*
+ * Validate that SET NOT NULL is ok for this chunk.
+ *
+ * Throws an error if SET NOT NULL on this chunk is not allowed, right now,
+ * SET NOT NULL is allowed on chunks that are either a fully decompressed, or
+ * are using the Hypercore table access method.
+ */
+static void
+validate_set_not_null(Hypertable *ht, Oid chunk_relid, void *arg)
+{
+	Chunk *chunk = ts_chunk_get_by_relid(chunk_relid, true);
+	if (ts_chunk_is_compressed(chunk) && !ts_is_hypercore_am(chunk->amoid))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("operation not supported on compressed chunks not using the "
+						"\"hypercore\" table access method"),
+				 errdetail("Chunk %s.%s is using the heap table access method and has compressed "
+						   "data.",
+						   NameStr(chunk->fd.schema_name),
+						   NameStr(chunk->fd.table_name)),
+				 errhint("Either decompress all chunks of the hypertable or use \"ALTER TABLE "
+						 "%s.%s SET ACCESS METHOD hypercore\" on all chunks to change access "
+						 "method.",
+						 NameStr(chunk->fd.schema_name),
+						 NameStr(chunk->fd.table_name))));
+	}
+}
+
+/*
+ * This function checks that we are not dropping NOT NULL from bad columns and
+ * that all chunks support the modification.
+ */
 static void
-process_altertable_drop_not_null(Hypertable *ht, AlterTableCmd *cmd)
+process_altertable_alter_not_null_start(Hypertable *ht, AlterTableCmd *cmd)
 {
 	int i;
 
+	if (cmd->subtype == AT_SetNotNull)
+		foreach_chunk(ht, validate_set_not_null, cmd);
+
+	if (cmd->subtype != AT_DropNotNull)
+		return;
+
 	for (i = 0; i < ht->space->num_dimensions; i++)
 	{
 		Dimension *dim = &ht->space->dimensions[i];
@@ -3803,9 +3843,10 @@ process_altertable_start_table(ProcessUtilityArgs *args)
 					verify_constraint_hypertable(ht, cmd->def);
 			}
 			break;
+			case AT_SetNotNull:
 			case AT_DropNotNull:
 				if (ht != NULL)
-					process_altertable_drop_not_null(ht, cmd);
+					process_altertable_alter_not_null_start(ht, cmd);
 				break;
 			case AT_AddColumn:
 #if PG16_LT
@@ -4187,6 +4228,8 @@ process_altertable_end_subcmd(Hypertable *ht, Node *parsetree, ObjectAddress *ob
 		case AT_DropCluster:
 			foreach_chunk(ht, process_altertable_chunk, cmd);
 			break;
+		case AT_SetNotNull:
+		case AT_DropNotNull:
 		case AT_SetRelOptions:
 		case AT_ResetRelOptions:
 		case AT_ReplaceRelOptions:
@@ -4213,8 +4256,6 @@ process_altertable_end_subcmd(Hypertable *ht, Node *parsetree, ObjectAddress *ob
 		case AT_SetStorage:
 		case AT_ColumnDefault:
 		case AT_CookedColumnDefault:
-		case AT_SetNotNull:
-		case AT_DropNotNull:
 		case AT_AddOf:
 		case AT_DropOf:
 		case AT_AddIdentity:
@@ -4494,8 +4535,8 @@ process_reassign_owned_start(ProcessUtilityArgs *args)
 			Oid newrole_oid = get_rolespec_oid(stmt->newrole, false);
 			HeapTuple tuple = ts_scanner_fetch_heap_tuple(ti, false, &should_free);
 
-			/* We do not need to check privileges here since ReassignOwnedObjects() will check the
-			 * privileges and error out if they are not correct. */
+			/* We do not need to check privileges here since ReassignOwnedObjects() will check
+			 * the privileges and error out if they are not correct. */
 			ts_bgw_job_update_owner(ti->scanrel, tuple, ts_scanner_get_tupledesc(ti), newrole_oid);
 
 			if (should_free)
@@ -4631,8 +4672,8 @@ process_create_stmt(ProcessUtilityArgs *args)
 				errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				errmsg("hypercore access method not supported on \"%s\"", stmt->relation->relname),
 				errdetail("The hypercore access method is only supported for hypertables."),
-				errhint("It does not make sense to set the default access method for all tables "
-						"to \"%s\" since it is only supported for hypertables.",
+				errhint("It does not make sense to set the default access method for all "
+						"tables to \"%s\" since it is only supported for hypertables.",
 						TS_HYPERCORE_TAM_NAME));
 
 	return DDL_CONTINUE;

tsl/src/hypercore/utils.c

@@ -12,6 +12,7 @@
 #include <catalog/pg_class.h>
 #include <commands/defrem.h>
 #include <nodes/makefuncs.h>
+#include <postgres_ext.h>
 #include <storage/lmgr.h>
 #include <storage/lockdefs.h>
 #include <utils/builtins.h>

tsl/test/expected/compression_ddl.out

@@ -2591,4 +2591,28 @@ SELECT count(*) FROM test2 WHERE i IS NULL;
      1
 (1 row)
 
-SET client_min_messages = NOTICE;
+SELECT count(compress_chunk(ch)) FROM show_chunks('test2') ch;
+ count 
+-------
+    28
+(1 row)
+
+SELECT count(*) FROM test2 WHERE i IS NULL;
+ count 
+-------
+     1
+(1 row)
+
+\set ON_ERROR_STOP 0
+ALTER TABLE test2 ALTER COLUMN i SET NOT NULL;
+ERROR:  operation not supported on compressed chunks not using the "hypercore" table access method
+DELETE FROM test2 WHERE i IS NULL;
+SELECT count(*) FROM test2 WHERE i IS NULL;
+ count 
+-------
+     0
+(1 row)
+
+ALTER TABLE test2 ALTER COLUMN i SET NOT NULL;
+ERROR:  operation not supported on compressed chunks not using the "hypercore" table access method
+\set ON_ERROR_STOP 1

tsl/test/expected/compression_errors-14.out

@@ -239,7 +239,7 @@ DETAIL:  Cannot drop column that is a hypertable partitioning (space or time) di
 ALTER TABLE foo DROP COLUMN b;
 ERROR:  cannot drop orderby or segmentby column from a hypertable with compression enabled
 ALTER TABLE foo ALTER COLUMN t SET NOT NULL;
-ERROR:  operation not supported on hypertables that have compression enabled
+ERROR:  column "t" of relation "_hyper_10_2_chunk" contains null values
 ALTER TABLE foo RESET (timescaledb.compress);
 ERROR:  compression options cannot be reset
 --can add constraints as long as no data is compressed

tsl/test/expected/compression_errors-15.out

@@ -239,7 +239,7 @@ DETAIL:  Cannot drop column that is a hypertable partitioning (space or time) di
 ALTER TABLE foo DROP COLUMN b;
 ERROR:  cannot drop orderby or segmentby column from a hypertable with compression enabled
 ALTER TABLE foo ALTER COLUMN t SET NOT NULL;
-ERROR:  operation not supported on hypertables that have compression enabled
+ERROR:  column "t" of relation "_hyper_10_2_chunk" contains null values
 ALTER TABLE foo RESET (timescaledb.compress);
 ERROR:  compression options cannot be reset
 --can add constraints as long as no data is compressed

tsl/test/expected/compression_errors-16.out

@@ -239,7 +239,7 @@ DETAIL:  Cannot drop column that is a hypertable partitioning (space or time) di
 ALTER TABLE foo DROP COLUMN b;
 ERROR:  cannot drop orderby or segmentby column from a hypertable with compression enabled
 ALTER TABLE foo ALTER COLUMN t SET NOT NULL;
-ERROR:  operation not supported on hypertables that have compression enabled
+ERROR:  column "t" of relation "_hyper_10_2_chunk" contains null values
 ALTER TABLE foo RESET (timescaledb.compress);
 ERROR:  compression options cannot be reset
 --can add constraints as long as no data is compressed

tsl/test/expected/compression_errors-17.out

@@ -239,7 +239,7 @@ DETAIL:  Cannot drop column that is a hypertable partitioning (space or time) di
 ALTER TABLE foo DROP COLUMN b;
 ERROR:  cannot drop orderby or segmentby column from a hypertable with compression enabled
 ALTER TABLE foo ALTER COLUMN t SET NOT NULL;
-ERROR:  operation not supported on hypertables that have compression enabled
+ERROR:  column "t" of relation "_hyper_10_2_chunk" contains null values
 ALTER TABLE foo RESET (timescaledb.compress);
 ERROR:  compression options cannot be reset
 --can add constraints as long as no data is compressed