On Fri, Feb 2, 2024 at 11:32 AM Richard Guo <guofengli...@gmail.com> wrote:
> On Fri, Feb 2, 2024 at 10:02 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > >> One of the test cases added by this commit has not been very >> stable in the buildfarm. Latest example is here: >> >> >> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=prion&dt=2024-02-01%2021%3A28%3A04 >> >> and I've seen similar failures intermittently on other machines. >> >> I'd suggest building this test atop a table that is more stable >> than pg_class. You're just waving a red flag in front of a bull >> if you expect stable statistics from that during a regression run. >> Nor do I see any particular reason for pg_class to be especially >> suited to the test. > > > Yeah, it's not a good practice to use pg_class in this place. While > looking through the test cases added by this commit, I noticed some > other minor issues that are not great. Such as > > * The table 'btg' is inserted with 10000 tuples, which seems a bit > expensive for a test. I don't think we need such a big table to test > what we want. > > * I don't see why we need to manipulate GUC max_parallel_workers and > max_parallel_workers_per_gather. > > * I think we'd better write the tests with the keywords being all upper > or all lower. A mixed use of upper and lower is not great. Such as in > > explain (COSTS OFF) SELECT x,y FROM btg GROUP BY x,y,z,w; > > * Some comments for the test queries are not easy to read. > > * For this statement > > CREATE INDEX idx_y_x_z ON btg(y,x,w); > > I think the index name would cause confusion. It creates an index on > columns y, x and w, but the name indicates an index on y, x and z. > > I'd like to write a draft patch for the fixes. > Here is the draft patch that fixes the issues I complained about in upthread. Thanks Richard
v1-0001-Multiple-revises-for-the-GROUP-BY-reordering-tests.patch
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