Previously we checked if an operator is in pg_catalog, and if it wasn't we prefixed it with namespace in worker queries. This can have a huge impact on performance of physical planner when using custom data types.
This happened regardless of current search_path config, because Citus overrides the search path in get_query_def_extended(). When we do so, the check for existence of the operator in current search path in generate_operator_name() fails for any operators outside pg_catalog. This means that nothing gets cached, and in the following calls we will again recheck the system tables for existence of the operators, which took an additional 40-50ms for some of the usecases we were seeing.
In this change we skip the pg_catalog check, and always prefix the operator with its namespace.
After this change all the logic related to shard data fetch logic
will be removed. Planner won't plan any ShardFetchTask anymore.
Shard fetch related steps in real time executor and task-tracker
executor have been removed.
This is the first of series of window function work.
We can now support window functions that can be pushed down to workers.
Window function must have distribution column in the partition clause
to be pushed down.
With #1804 (and related PRs), Citus gained the ability to
plan subqueries that are not safe to pushdown.
There are two high-level requirements for pushing down subqueries:
* Individual subqueries that require a merge step (i.e., GROUP BY
on non-distribution key, or LIMIT in the subquery etc). We've
handled such subqueries via #1876.
* Combination of subqueries that are not joined on distribution keys.
This commit aims to recursively plan some of such subqueries to make
the whole query safe to pushdown.
The main logic behind non colocated subquery joins is that we pick
an anchor range table entry and check for distribution key equality
of any other subqueries in the given query. If for a given subquery,
we cannot find distribution key equality with the anchor rte, we
recursively plan that subquery.
We also used a hacky solution for picking relations as the anchor range
table entries. The hack is that we wrap them into a subquery. This is only
necessary since some of the attribute equivalance checks are based on
queries rather than range table entries.
Hadi Moshayedi
velioglu
Murat Tuncer
Onder Kalaci
Marco Slot