Schema Diff: drop the scaffolding default partition after rebuilding a partitioned table

web/pgadmin/browser/server_groups/servers/databases/schemas/tables/partitions/__init__.py

@@ -497,11 +497,29 @@ def get_sql_from_diff(self, **kwargs):
         target_data['orig_name'] = target_data['name']
         target_data['name'] = 'temp_partitioned_{0}'.format(
             secrets.choice(range(1, 9999999)))
+
+        # If the source table already has a default partition of its own,
+        # it will be (re)created below via source_data['partitions'], so we
+        # must not scaffold an extra one (Postgres allows only a single
+        # default partition per parent). We only need the scaffolding
+        # default partition - dropped again once the data copy is done -
+        # when the source has no default partition, to prevent the
+        # row-copy INSERT from failing on rows that don't match any of the
+        # real partitions.
+        source_has_default_partition = any(
+            partition.get('is_default') for partition in
+            source_data.get('partitions', []))
+        target_data['create_scaffolding_default_partition'] = \
+            not source_has_default_partition
+
         # For PG/EPAS 11 and above when we copy the data from original
         # table to temporary table for schema diff, we will have to create
-        # a default partition to prevent the data loss.
+        # a default partition to prevent the data loss. Derive its name
+        # from the already-randomised temporary table name (rather than
+        # the original table's name) so it cannot collide with an
+        # existing relation.
         target_data['default_partition_name'] = \
-            target_data['orig_name'] + '_default'
+            target_data['name'] + '_default'
 
         # Copy the partition scheme from source to target.
         if 'partition_scheme' in source_data:

web/pgadmin/browser/server_groups/servers/databases/schemas/tables/schema_diff_table_utils.py

@@ -322,6 +322,20 @@ def get_sql_from_submodule_diff(self, **kwargs):
         pk_diff = self.table_constraint_comp(source, target)
         diff_dict.update(pk_diff)
 
+        # When both the source and target tables are partitioned, the
+        # 'partition' submodule branch below rebuilds the whole table
+        # (and every one of its partitions) from scratch, handling any
+        # added, removed or bound-changed partition itself. The generic
+        # partition add/remove handling in get_sql_from_table_diff (via
+        # _check_for_partitions_in_sql) must not also run in that case:
+        # it would detach/recreate the same partitions using their real
+        # names ahead of the rebuild script, so the rebuild's row-copy
+        # step (which reads from the original table) would miss rows
+        # already detached out from under it, silently losing data.
+        if 'partitions' in diff_dict and \
+                source.get('is_partitioned') and target.get('is_partitioned'):
+            del diff_dict['partitions']
+
         # Get the difference DDL/DML statements for table
         target_params['diff_data'] = diff_dict
         diff = self.get_sql_from_table_diff(**target_params)

web/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/pg/default/partition_diff.sql

@@ -1,15 +1,32 @@
 CREATE TABLE IF NOT EXISTS {{conn|qtIdent(data.schema, data.name)}} (
     LIKE {{conn|qtIdent(data.schema, data.orig_name)}} INCLUDING ALL
 ) PARTITION BY {{ data.partition_scheme }};
-{{partition_sql}}{{partition_data.default_partition_header}}
+{{partition_sql}}{% if data.create_scaffolding_default_partition %}{{partition_data.default_partition_header}}
 CREATE TABLE IF NOT EXISTS {{conn|qtIdent(data.schema, data.default_partition_name)}} PARTITION OF {{conn|qtIdent(data.schema, data.name)}} DEFAULT;
-
+{% endif %}
 INSERT INTO {{conn|qtIdent(data.schema, data.name)}}(
 {% if data.columns and data.columns|length > 0 %}
 {% for c in data.columns %} {{c.name}}{% if not loop.last %},{% endif %}{% endfor %}{% endif %})
 SELECT {% if data.columns and data.columns|length > 0 %}{% for c in data.columns %}{{c.name}}{% if not loop.last %},{% endif %}{% endfor %}{% endif %}
  FROM {{conn|qtIdent(data.schema, data.orig_name)}};
-
+{% if data.create_scaffolding_default_partition %}
+-- The source table has no default partition of its own, so the
+-- scaffolding default partition created above (purely to stop the row
+-- copy above failing on unmatched rows) is dropped, but only if it is
+-- still empty. If any rows were routed into it (i.e. rows that don't
+-- fall within the bounds of any other partition), it is left in place
+-- so that data is not lost; it becomes the default partition of the
+-- rebuilt table.
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM {{conn|qtIdent(data.schema, data.default_partition_name)}}
+    ) THEN
+        DROP TABLE {{conn|qtIdent(data.schema, data.default_partition_name)}};
+    END IF;
+END;
+$$;
+{% endif %}
 {% if partition_data.partitions and partition_data.partitions|length > 0 %}
 {% for part in partition_data.partitions %}
 DROP TABLE IF EXISTS {{conn|qtIdent(data.schema, part.partition_name)}};

web/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/ppas/default/partition_diff.sql

@@ -1,15 +1,32 @@
 CREATE TABLE {{conn|qtIdent(data.schema, data.name)}} (
     LIKE {{conn|qtIdent(data.schema, data.orig_name)}} INCLUDING ALL
 ) PARTITION BY {{ data.partition_scheme }};
-{{partition_sql}}{{partition_data.default_partition_header}}
+{{partition_sql}}{% if data.create_scaffolding_default_partition %}{{partition_data.default_partition_header}}
 CREATE TABLE IF NOT EXISTS {{conn|qtIdent(data.schema, data.default_partition_name)}} PARTITION OF {{conn|qtIdent(data.schema, data.name)}} DEFAULT;
-
+{% endif %}
 INSERT INTO {{conn|qtIdent(data.schema, data.name)}}(
 {% if data.columns and data.columns|length > 0 %}
 {% for c in data.columns %} {{c.name}}{% if not loop.last %},{% endif %}{% endfor %}{% endif %})
 SELECT {% if data.columns and data.columns|length > 0 %}{% for c in data.columns %}{{c.name}}{% if not loop.last %},{% endif %}{% endfor %}{% endif %}
  FROM {{conn|qtIdent(data.schema, data.orig_name)}};
-
+{% if data.create_scaffolding_default_partition %}
+-- The source table has no default partition of its own, so the
+-- scaffolding default partition created above (purely to stop the row
+-- copy above failing on unmatched rows) is dropped, but only if it is
+-- still empty. If any rows were routed into it (i.e. rows that don't
+-- fall within the bounds of any other partition), it is left in place
+-- so that data is not lost; it becomes the default partition of the
+-- rebuilt table.
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM {{conn|qtIdent(data.schema, data.default_partition_name)}}
+    ) THEN
+        DROP TABLE {{conn|qtIdent(data.schema, data.default_partition_name)}};
+    END IF;
+END;
+$$;
+{% endif %}
 {% if partition_data.partitions and partition_data.partitions|length > 0 %}
 {% for part in partition_data.partitions %}
 DROP TABLE IF EXISTS {{conn|qtIdent(data.schema, part.partition_name)}};