PG16 compatibility - part 9
Check out part 1 42d956888d
part 2 0d503dd5ac
part 3 907d72e60d
part 4 7c6b4ce103
part 5 6056cb2c29
part 6 b36c431abb
part 7 ee3153fe50
part 8 2c50b5f7ff
This commit is in the series of PG16 compatibility commits. It makes some changes
to our tests in order to be compatible with the following in PG16:
- Fix multi_subquery_in_where_reference_clause test
somehow PG got rid of the outer join
(e.g., explain doesn't show outer joins),
hence we can pushdown the subquery.
Changing to users_reference_table
- Fix unqualified column names for views in PG16
Relevant PG commit:
47bb9db759
47bb9db75996232ea71fc1e1888ffb0e70579b54
- Fix global_cancel test
Error wording and detail changed
Relevant PG commit:
2631ebab7b
2631ebab7b18bdc079fd86107c47d6104a6b3c6e
- Fix local_table_join_test with lateral subquery
Possible relevant PG commit:
ae89129aa3
ae89129aa3555c263b8c3ccc4c0f1ef7e46201aa
I removed the where clause and the limit count error was hit again.
With the where clause the query unexpectedly works.
- Fix test outputs
Relevant PG commits:
-- 1349d2790b
-- f4c7c410ee
For multi_explain and multi_complex_count_distinct there were too many places
touched so I just added an alternative test output.
For the other tests I modified the problematic parts.
More PG16 compatibility commits are coming soon ...
DESCRIPTION: Replace the query planner for the coordinator part with the postgres planner
Closes#2761
Citus had a simple rule based planner for the query executed on the query coordinator. This planner grew over time with the addigion of SQL support till it was getting close to the functionality of the postgres planner. Except the code was brittle and its complexity rose which made it hard to add new SQL support.
Given its resemblance with the postgres planner it was a long outstanding wish to replace our hand crafted planner with the well supported postgres planner. This patch replaces our planner with a call to postgres' planner.
Due to the functionality of the postgres planner we needed to support both projections and filters/quals on the citus custom scan node. When a sort operation is planned above the custom scan it might require fields to be reordered in the custom scan before returning the tuple (projection). The postgres planner assumes every custom scan node implements projections. Because we controlled the plan that was created we prevented reordering in the custom scan and never had implemented it before.
A same optimisation applies to having clauses that could have been where clauses. Instead of applying the filter as a having on the aggregate it will push it down into the plan which could reach a custom scan node.
For both filters and projections we have implemented them when tuples are read from the tuple store. If no projections or filters are required it will directly return the tuple from the tuple store. Otherwise it will loop tuples from the tuple store through the filter and projection until a tuple is found and returned.
Besides filters being pushed down a side effect of having quals that could have been a where clause is that a call to read intermediate result could be called before the first tuple is fetched from the custom scan. This failed because the intermediate result would only be pulled to the coordinator on the first tuple fetch. To overcome this problem we do run the distributed subplans now before we run the postgres executor. This ensures the intermediate result is present on the coordinator in time. We do account for total time instrumentation by removing the instrumentation before handing control to the psotgres executor and update the timings our self.
For future SQL support it is enough to create a valid query structure for the part of the query to be executed on the query coordinating node. As a utility we do serialise and print the query at debug level4 for engineers to inspect what kind of query is being planned on the query coordinator.
- changes in ruleutils_11.c is reflected
- vacuum statement api change is handled. We now allow
multi-table vacuum commands.
- some other function header changes are reflected
- api conflicts between PG11 and earlier versions
are handled by adding shims in version_compat.h
- various regression tests are fixed due output and
functionality in PG1
- no change is made to support new features in PG11
they need to be handled by new commit
We push down order by to worker query when limit is specified
(with some other additional checks). If the query has an expression
on an aggregate or avg aggregate by itself, and there is an order
by on this particular target we may send wrong order by to worker
query with potential to affect query result.
The fix creates a auxilary target entry in the worker query and
uses that target entry for sorting.
Naisila Puka
Nils Dijk
Philip Dubé
Murat Tuncer
Murat Tuncer