Horton

Re: executor relation handling

Amit Langote <langote_amit_f8@lab.ntt.co.jp>

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From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
To: Pg Hackers <pgsql-hackers@postgresql.org>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, David Rowley <dgrowleyml@gmail.com>
Date: 2018-09-04T08:53:11Z
Lists: pgsql-hackers

Attachments

On 2018/08/16 17:22, Amit Langote wrote:
> 0004-Revise-executor-range-table-relation-opening-closing.patch
> 
> This adds two arrays to EState indexed by RT indexes, one for
> RangeTblEntry's and another for Relation pointers.  The former reduces the
> cost of fetching RangeTblEntry by RT index.  The latter is used by a newly
> introduced function ExecRangeTableRelation(), which replaces heap_open for
> relations that are contained in the range table.  If a given RTE's
> relation is opened by multiple times, only the first call of
> ExecRangeTableRelation will go to relcache.

David Rowely recently, independently [1], proposed one of the ideas
mentioned above (store RangeTblEntry's in an array in EState).  As I
mentioned in reply to his email, I think his implementation of the idea is
better than mine, so I've merged his patch in the above patch, except one
part: instead of removing the es_range_table list altogether, I decided to
keep it around so that ExecSerializePlan doesn't have to build one all
over again from the array like his patch did.

Updated patches attached; 0001-0003 are same as v1.

Thanks,
Amit

[1] Make executor's Range Table an array instead of a List
https://postgr.es/m/CAKJS1f9EypD_=xG6ACFdF=1cBjz+Z9hiHHSd-RqLjor+QyA-nw@mail.gmail.com

Commits

  1. Avoid O(N^2) cost in ExecFindRowMark().

  2. Remove some unnecessary fields from Plan trees.

  3. Restore sane locking behavior during parallel query.

  4. Remove more redundant relation locking during executor startup.

  5. In the executor, use an array of pointers to access the rangetable.

  6. Centralize executor's opening/closing of Relations for rangetable entries.

  7. Change executor to just Assert that table locks were already obtained.

  8. Change rewriter/planner/executor/plancache to depend on RTE rellockmode.

  9. Add assertions that we hold some relevant lock during relation open.

  10. Create an RTE field to record the query's lock mode for each relation.