Horton

Re: executor relation handling

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Cc: David Rowley <david.rowley@2ndquadrant.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Jesper Pedersen <jesper.pedersen@redhat.com>, Amit Langote <amitlangote09@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-10-07T18:55:07Z
Lists: pgsql-hackers 
Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> writes:
> 0004: removes useless fields from certain planner nodes whose only purpose
> has been to assist the executor lock relations in proper order

I've pushed most of 0004 now; obviously, not the parts removing
PlannedStmt.rowMarks, since that's not possible without rearrangement
of the executor's RowMark handling.

I didn't like the idea of unifying ModifyTable.nominalRelation with
the partition root info.  Those fields serve different masters ---
nominalRelation, at least in its original intent, is only meant for
use of EXPLAIN and might have nothing to do with what happens at
execution.  So even though unifying them would work today, we might
regret it down the line.  Instead I left that field alone and added
a separate rootRelation field to carry the partition root RT index,
which ends up being the same number of fields anyway since we don't
need a flag for is-the-nominal-relation-a-partition-root.

Still need to think a bit more about whether we want 0005 in
anything like its current form.

			regards, tom lane

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.