Cannot add dimension if table has empty chunks

add_dimension should fail when table has no
data but still has empty chunks.
Fixes #1623

CHANGELOG.md

@@ -13,6 +13,7 @@ accidentally triggering the load of a previous DB version.**
 **Bugfixes**
 * #1648 Drop chunks for materialized hypertable
 * #1665 Add ignore_invalidation_older_than to timescaledb_information.continuous_aggregates view
+* #1668 Cannot add dimension if hypertable has empty chunks
 * #1674 Fix time_bucket_gapfill's interaction with GROUP BY
 
 **Thanks**

src/dimension.c

@@ -1355,11 +1355,13 @@ ts_dimension_add(PG_FUNCTION_ARGS)
 
 	if (!info.skip)
 	{
-		if (ts_hypertable_has_tuples(info.table_relid, AccessShareLock))
+		if (ts_hypertable_has_chunks(info.table_relid, AccessShareLock))
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("hypertable \"%s\" is not empty", get_rel_name(info.table_relid)),
-					 errdetail("It is not possible to add dimensions to a non-empty hypertable")));
+					 errmsg("hypertable \"%s\" has tuples or empty chunks",
+							get_rel_name(info.table_relid)),
+					 errdetail("It is not possible to add dimensions to a hypertable that has "
+							   "chunks. Please truncate the table.")));
 
 		/*
 		 * Note that space->num_dimensions reflects the actual number of

src/hypertable.c

@@ -1250,6 +1250,16 @@ ts_hypertable_has_tuples(Oid table_relid, LOCKMODE lockmode)
 	return false;
 }
 
+bool
+ts_hypertable_has_chunks(Oid table_relid, LOCKMODE lockmode)
+{
+	List *chunks = find_inheritance_children(table_relid, lockmode);
+	if (chunks != NIL)
+		return true;
+	else
+		return false;
+}
+
 static void
 hypertable_create_schema(const char *schema_name)
 {

src/hypertable.h

@@ -114,6 +114,7 @@ extern char *ts_hypertable_select_tablespace_name(Hypertable *ht, Chunk *chunk);
 extern Tablespace *ts_hypertable_get_tablespace_at_offset_from(int32 hypertable_id,
 															   Oid tablespace_oid, int16 offset);
 extern bool ts_hypertable_has_tuples(Oid table_relid, LOCKMODE lockmode);
+extern bool ts_hypertable_has_chunks(Oid table_relid, LOCKMODE lockmode);
 extern void ts_hypertables_rename_schema_name(const char *old_name, const char *new_name);
 extern List *ts_hypertable_get_all_by_name(Name schema_name, Name table_name, MemoryContext mctx);
 extern bool ts_is_partitioning_column(Hypertable *ht, Index column_attno);

test/expected/create_hypertable.out

@@ -238,10 +238,10 @@ ERROR:  cannot specify both the number of partitions and an interval
 --adding a new dimension on a non-empty table should also fail
 insert into test_schema.test_table values (123456789, 23.8, 'blue', 'type1', 'nyc', 1, 1);
 select add_dimension('test_schema.test_table', 'device_type', 2);
-ERROR:  hypertable "test_table" is not empty
+ERROR:  hypertable "test_table" has tuples or empty chunks
 -- should fail on non-empty table with 'if_not_exists' in case the dimension does not exists
 select add_dimension('test_schema.test_table', 'device_type', 2, if_not_exists => true);
-ERROR:  hypertable "test_table" is not empty
+ERROR:  hypertable "test_table" has tuples or empty chunks
 \set ON_ERROR_STOP 1
 -- should not fail on non-empty table with 'if_not_exists' in case the dimension exists
 select add_dimension('test_schema.test_table', 'location', 2, if_not_exists => true);
@@ -251,6 +251,18 @@ NOTICE:  column "location" is already a dimension, skipping
  (5,test_schema,test_table,location,f)
 (1 row)
 
+--should fail on empty table that still has chunks --
+\set ON_ERROR_STOP 0
+delete from test_schema.test_table where time is not null;
+select count(*) from test_schema.test_table;
+ count 
+-------
+     0
+(1 row)
+
+select add_dimension('test_schema.test_table', 'device_type', 2);
+ERROR:  hypertable "test_table" has tuples or empty chunks
+\set ON_ERROR_STOP 1
 --show chunks in the associated schema
 \dt "chunk_schema".*
                       List of relations

test/sql/create_hypertable.sql

@@ -135,6 +135,13 @@ select add_dimension('test_schema.test_table', 'device_type', 2, if_not_exists =
 -- should not fail on non-empty table with 'if_not_exists' in case the dimension exists
 select add_dimension('test_schema.test_table', 'location', 2, if_not_exists => true);
 
+--should fail on empty table that still has chunks --
+\set ON_ERROR_STOP 0
+delete from test_schema.test_table where time is not null;
+select count(*) from test_schema.test_table;
+select add_dimension('test_schema.test_table', 'device_type', 2);
+\set ON_ERROR_STOP 1
+
 --show chunks in the associated schema
 \dt "chunk_schema".*