Schema Diff: drop the scaffolding default partition after rebuilding a partitioned table - #10316
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…a partitioned table (pgadmin-org#10301) Rebuilding a partitioned table (e.g. because its partition key changed) generates a script that creates a temporary partitioned table, adds a DEFAULT partition to it purely so the row-copy INSERT doesn't fail on rows that match none of the real partitions, copies the rows across and renames everything into place. The scaffolding DEFAULT partition was never removed, so a source table with no default partition of its own ended up with an extra one in the rebuilt target, and Schema Diff would report the table as different forever after. Worse, if the source table did have a genuine default partition, the generated script tried to create it as well as the scaffolding one, and Postgres only allows a single DEFAULT partition per parent, so applying the script failed outright. get_sql_from_diff() now checks whether the source table already has a default partition and only asks the template to scaffold one when it doesn't; partition_diff.sql only creates that scaffolding partition (and drops it again once the row copy is done) in that case, leaving a genuine source default partition to be carried across, renamed into place, by the normal per-partition rename loop. Added test_schema_diff_partition_default.py, covering both a source table without a default partition (the scaffolding one must be dropped) and one with a genuine default partition (it must survive and the script must not attempt to create two).
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WalkthroughSchema Diff now detects source default partitions before rebuilding partitioned tables. PostgreSQL and PPAS templates conditionally create and remove temporary default partitions. A regression test validates rebuilds with and without source default partitions. ChangesPartition default scaffolding
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: 🟠 High · up to The rebuild script now creates and removes a temporary default partition, but its fixed name can collide with an existing relation and rows routed there can be deleted during cleanup. The PR is not safe to merge until the scaffold uses a unique name and non-empty scaffolding is handled without data loss. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Inline comments:
In
`@web/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/pg/default/partition_diff.sql`:
- Around line 4-16: Update the scaffold default-partition name in both
web/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/pg/default/partition_diff.sql
lines 4-16 and
web/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/ppas/default/partition_diff.sql
lines 4-16 to derive it from the randomized temporary table name, and use that
same unique name for creation and DROP TABLE cleanup; no other changes are
needed.
- Around line 12-16: Before dropping the scaffolding default partition, validate
that it is empty and abort if it contains rows; update the conditional block in
partition_diff.sql for both
web/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/pg/default/partition_diff.sql
lines 12-16 and
web/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/ppas/default/partition_diff.sql
lines 12-16. Preserve the existing DROP TABLE behavior only for an empty
scaffold.
In `@web/pgadmin/tools/schema_diff/tests/test_schema_diff_partition_default.py`:
- Around line 37-81: Extend the schema-diff fixture test around DDL_SOURCE and
DDL_TARGET to insert rows into both the regular and DEFAULT partitions of each
target table before rebuilding. After each rebuild, assert the expected row
counts in the corresponding partitions, covering INSERT ... SELECT data copying
and routing for both partition configurations.
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web/pgadmin/browser/server_groups/servers/databases/schemas/tables/partitions/__init__.pyweb/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/pg/default/partition_diff.sqlweb/pgadmin/browser/server_groups/servers/databases/schemas/tables/templates/partitions/sql/ppas/default/partition_diff.sqlweb/pgadmin/tools/schema_diff/tests/test_schema_diff_partition_default.py
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scaffold default partitions, and skip redundant partition ALTER diff Address CodeRabbit review findings on the partitioned-table rebuild added in pgadmin-org#10301: - The scaffolding default partition's name was derived from the original table's name (<table>_default), a deterministic name that can collide with an existing relation. Derive it from the already string.randomised temporary table name instead, matching the collision-avoidance convention already used for the temp partitioned table and its temp partitions. - The scaffolding default partition was unconditionally dropped once the row copy finished. Any row from the source table that fell outside every real partition's bounds landed in that scaffold and was silently destroyed. The generated SQL now only drops the scaffold if it is still empty; otherwise it is kept, so the rows it caught survive as the default partition of the rebuilt table. - Separately, found and fixed a data-loss bug this exposed: whenever a table's partitions differ on both source and target, the generic table-diff also ran its own ALTER-based partition add/remove/detach logic (get_sql_from_table_diff/_check_for_partitions_in_sql) alongside the full-table rebuild path in schema_diff_table_utils.py. Because that generic path detaches a bound-changed partition using its real name before the rebuild's row-copy INSERT ... SELECT runs against the original table, the detached partition's rows were invisible to that copy and got dropped when the rebuild's own cleanup step removed the now-standalone table - causing the run-python-tests-pg/run-feature-tests-pg CI failures on PR pgadmin-org#10316. The generic partition diffing is now skipped whenever both sides are partitioned, since the rebuild path already handles every partition difference itself. - Strengthened the regression test: both fixtures now carry real rows (including rows that only fit a DEFAULT partition, and a row outside every rebuilt partition's bounds) so the row-copy and row-routing paths are actually exercised, not just the DDL shape.
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What this is
Rebuilding a partitioned table (e.g. because its partition key changed) generates a script that creates a temporary partitioned table, adds a
DEFAULTpartition to it purely so the row-copyINSERTdoesn't fail on rows that match none of the real partitions, copies the rows across, and renames everything into place. The scaffoldingDEFAULTpartition was never removed, so a source table with no default partition of its own ended up with an extra one in the rebuilt target, and Schema Diff reported the table as different forever after.Worse, if the source table did have a genuine default partition, the generated script tried to create it as well as the scaffolding one, and PostgreSQL only allows a single
DEFAULTpartition per parent, so applying the script failed outright.The fix
get_sql_from_diff()now checks whether the source table already has a default partition and only asks the template to scaffold one when it doesn't;partition_diff.sqlonly creates that scaffolding partition (and drops it again once the row copy is done) in that case, leaving a genuine source default partition to be carried across, renamed into place, by the normal per-partition rename loop.Testing
Added
test_schema_diff_partition_default.py, covering both a source table without a default partition (the scaffolding one must be dropped) and one with a genuine default partition (it must survive and the script must not attempt to create two).tools.schema_diffandbrowser.server_groups.servers.databases.schemas.tables(473 tests) pass against PostgreSQL 18;pycodestyleis clean.Fixes #10301.
Summary by CodeRabbit
Bug Fixes
Tests