Push down all JOIN expressions as JOIN expressions
Maintainers usually reply within 1 day
Nobody has claimed this yet.
Assessment
- Difficulty
- 5/5
- Estimated time
- Over a week
- Newbie friendliness
- 35/100
Research direction
Start by tracing foreign_join_ok() and the code that moves non-key expressions into remote conditions. Compare how INNER JOIN and SEMI JOIN conditions are handled, then identify existing tests or query-planning checks for these paths; the issue is complete only when the intended pushdown behavior and its efficiency implications are established.
Written by the indexing model from the issue text.
Description
Currently, foreign_join_ok() uses only JOIN key expressions in INNER JOIN and SEMI JOIN expressions: that is, only expressions that reference both the right and left keys using the equality operator. The rest are appended to remote conditions for use in the WHERE clause.
I suspect that ClickHouse used to allow only join key expressions but opened it up to additional expressions later. Today at least one must be a join key expression but other expressions are allowed.
Would it make sense to allow all expressions to be pushed down as JOIN expressions, rather than filtering some to remote conditions (the WHERE clause)? Seems like there might be some efficiencies in that, although maybe the ClickHouse optimizer adjusts appropriately to save cycles and iops?
- Dominant language
- C
- Stars
- 284
- Forks
- 21
- Avg merge
- 23h 1m
- Merged PRs (30d)
- 20
Getting set up
We have not checked this project's setup files yet. Start from its README, and see our first-contribution guide for the general steps.
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
More from ClickHouse/pg_clickhouse
-
documentation
Difficulty 1/5 1-3 hours Newbie friendliness 88/100
ClickHouse/pg_clickhouse#383 · 2 comments ·
Maintainers usually reply within 1 day
-
Difficulty 3/5 1-2 days Newbie friendliness 76/100
ClickHouse/pg_clickhouse#386 ·
Maintainers usually reply within 1 day
-
data types enhancement
Difficulty 5/5 Over a week Newbie friendliness 35/100
ClickHouse/pg_clickhouse#380 ·
Maintainers usually reply within 1 day
-
enhancement functions pushdown
Difficulty 3/5 1-2 days Newbie friendliness 68/100
ClickHouse/pg_clickhouse#379 ·
Maintainers usually reply within 1 day
-
Push down joins against an aggregated `IN (SELECT … GROUP BY … HAVING)` subquery (TPC-H Q18 shape)Possibly taken @JoshDreamland claimed this 3 days ago. Openenhancement pushdown sql
ClickHouse/pg_clickhouse#378 · 1 assignee ·
Maintainers usually reply within 1 day
All issues in ClickHouse/pg_clickhouse
Similar issues
-
Difficulty 2/5 1-3 hours Newbie friendliness 90/100
BasedHardware/omi#19711 ·
Maintainers usually reply within 1 day
-
Difficulty 2/5 1-3 hours Newbie friendliness 85/100
microsoft/ebpf-for-windows#5604 ·
Maintainers usually reply within 3 days
-
Difficulty 2/5 1-3 hours Newbie friendliness 68/100
trezor/trezor-firmware#7985 ·
Maintainers usually reply within 2 days
-
Difficulty 2/5 1-3 hours Newbie friendliness 84/100
Maintainers usually reply within 1 day
-
Difficulty 2/5 1-3 hours Newbie friendliness 70/100
Maintainers usually reply within 2 days