diff's query should account for table having no columns (#1256)

server/src-lib/Hasura/RQL/DDL/Schema/Diff.hs

@@ -58,7 +58,7 @@ fetchTableMeta = do
         t.table_schema,
         t.table_name,
         t.table_oid,
-        c.columns,
+        coalesce(c.columns, '[]') as columns,
         coalesce(f.constraints, '[]') as constraints
     FROM
         (SELECT
@@ -72,7 +72,7 @@ fetchTableMeta = do
            ON
              c.relnamespace = n.oid
         ) t
-        INNER JOIN
+        LEFT OUTER JOIN
         (SELECT
              table_schema,
              table_name,

server/tests-py/queries/v1/ddl/drop_no_cols_table.yaml

@@ -0,0 +1,32 @@
+url: /v1/query
+status: 200
+response:
+- {result: null, result_type: CommandOk}
+- {message: success}
+- {result: null, result_type: CommandOk}
+- []
+query:
+  type: bulk
+  args:
+    - type: run_sql
+      args:
+        sql: |
+          create table hge_tests.t ();
+    - type: track_table
+      args:
+        schema: hge_tests
+        name: t
+    - type: run_sql
+      args:
+        sql: |
+          drop table hge_tests.t;
+    - type: select
+      args:
+        table:
+          schema: hdb_catalog
+          name: hdb_table
+        columns:
+        - table_name
+        where:
+          table_name: t
+          table_schema: hge_tests

server/tests-py/test_v1_queries.py

@@ -2,6 +2,9 @@ import yaml
 from validate import check_query_f
 from super_classes import DefaultTestSelectQueries, DefaultTestQueries
 
+class TestDropNoColsTable:
+    def test_drop_no_cols_table(self, hge_ctx):
+        check_query_f(hge_ctx, 'queries/v1/ddl/drop_no_cols_table.yaml')
 
 class TestV1General(DefaultTestQueries):