On 28 September 2018 at 15:12, Michael Paquier <mich...@paquier.xyz> wrote: > On Fri, Sep 28, 2018 at 02:46:30PM +1200, David Rowley wrote: >> I don't agree that we can skip explaining why one of the optimisations >> can't be applied just because we've explained why a similar >> optimisation cannot be applied somewhere close by. I think that the >> WAL/FSM optimisation can fairly easily be improved on and probably >> fixed in PG12 as we can just lazily determine per-partition if it can >> be applied to that partition or not. > > Have you guys looked at what the following patch does for partitions and > how it interacts with it? > https://commitfest.postgresql.org/19/528/
I've glanced at it. I don't think we're taking anything in the wrong direction. The patch looks like it would need rebased if this gets in first. > The proposed patch is missing the point that documentation also mentions > the optimizations for COPY with wal_level = minimal: > <para> > <command>COPY</command> is fastest when used within the same > transaction as an earlier <command>CREATE TABLE</command> or > <command>TRUNCATE</command> command. In such cases no WAL > needs to be written, because in case of an error, the files > containing the newly loaded data will be removed anyway. > However, this consideration only applies when > <xref linkend="guc-wal-level"/> is <literal>minimal</literal> as all > commands > must write WAL otherwise. > </para> I've edited that in the attached patch. Also reworded a comment that Amit mentioned and made a small change to the COPY FREEZE docs to mention no support for partitioned tables. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
fix_incorrect_setting_of_hi_options_for_partitioned_tables_v2.patch
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