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Re: [PoC] Reducing planning time when tables have many partitions

Andrei Lepikhov <a.lepikhov@postgrespro.ru>

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From: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
To: Yuya Watari <watari.yuya@gmail.com>, David Rowley <dgrowleyml@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Thom Brown <thom@linux.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Zhang Mingli <zmlpostgres@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2023-09-19T08:21:15Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Update wording in optimizer/README for EquivalenceClasses

  2. Speedup child EquivalenceMember lookup in planner

  3. Allow planner to use Merge Append to efficiently implement UNION

  4. Remove trailing zero words from Bitmapsets

  5. Make Vars be outer-join-aware.

  6. Avoid making commutatively-duplicate clauses in EquivalenceClasses.

On 25/8/2023 14:39, Yuya Watari wrote:
> Hello,
> 
> On Wed, Aug 9, 2023 at 8:54 PM David Rowley <dgrowleyml@gmail.com> wrote:
>> I think the best way to move this forward is to explore not putting
>> partitioned table partitions in EMs and instead see if we can
>> translate to top-level parent before lookups.  This might just be too
>> complex to translate the Exprs all the time and it may add overhead
>> unless we can quickly determine somehow that we don't need to attempt
>> to translate the Expr when the given Expr is already from the
>> top-level parent. If that can't be made to work, then maybe that shows
>> the current patch has merit.
> 
> Based on your suggestion, I have experimented with not putting child
> EquivalenceMembers in an EquivalenceClass. I have attached a new
> patch, v20, to this email. The following is a summary of v20.
Working on self-join removal in the thread [1] nearby, I stuck into the 
problem, which made an additional argument to work in this new direction 
than a couple of previous ones.
With indexing positions in the list of equivalence members, we make some 
optimizations like join elimination more complicated - it may need to 
remove some clauses and equivalence class members.
For changing lists of derives or ec_members, we should go through all 
the index lists and fix them, which is a non-trivial operation.

[1] 
https://www.postgresql.org/message-id/flat/64486b0b-0404-e39e-322d-0801154901f3%40postgrespro.ru

-- 
regards,
Andrey Lepikhov
Postgres Professional