Horton

Re: Consider low startup cost in add_partial_path

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: James Coleman <jtc331@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-04-05T14:14:49Z
Lists: pgsql-hackers

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Hi,

For the record, here is the relevant part of the Incremental Sort patch
series, updating add_partial_path and add_partial_path_precheck to also
consider startup cost.

The changes in the first two patches are pretty straight-forward, plus
there's a proposed optimization in the precheck function to only run
compare_pathkeys if entirely necessary. I'm currently evaluating those
changes and I'll post the results to the incremental sort thread.


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Consider startup cost as a figure of merit for partial paths.

  2. Fix add_partial_path interaction with disabled_nodes

  3. Support parallel joins, and make related improvements.