From: | Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> |
---|---|
To: | Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: WIP: Collecting statistics on CSV file data |
Date: | 2011-10-18 05:45:19 |
Message-ID: | 4E9D126F.5010508@lab.ntt.co.jp |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
(2011/10/18 2:27), Shigeru Hanada wrote:
> The new patch could be applied with some shifts. Regression tests of
> core and file_fdw have passed cleanly. Though I've tested only simple
> tests, ANALYZE works for foreign tables for file_fdw, and estimation of
> costs and selectivity seem appropriate.
Thank you for your testing.
> New API AnalyzeForeignTable
> ===========================
> And I think that AnalyzeForeignTable should be optional, and it would be
> very useful if a default handler is provided. Probably a default
> handler can use basic FDW APIs to acquire sample rows from the result of
> "SELECT * FROM foreign_table" with skipping periodically. It won't be
> efficient but I think it's not so unreasonable.
I agree with you. However, I think that it is difficult to support such
a default handler in a unified way because there exist external data
sources for which we cannot execute "SELECT * FROM foreign_table", e.g.,
web-accessible DBs limiting full access to the contents.
> Other issues
> ============
> There are some other comments about non-critical issues.
> - When there is no analyzable column, vac_update_relstats is not called.
> Is this behavior intentional?
> - psql can't complete foreign table name after ANALYZE.
> - A new parameter has been added to vac_update_relstats in a recent
> commit. Perhaps 0 is OK for that parameter.
I'll check.
> - ANALYZE without relation name ignores foreign tables because
> get_rel_oids doesn't list foreign tables.
I think that it might be better to ignore foreign tables by default
because analyzing such tables may take long depending on FDW.
> - IMO logging "analyzing foo.bar" should not be done in
> AnalyzeForeignTable handler of each FDW because some FDW might forget to
> do it. Maybe it should be pulled up to analyze_rel or somewhere in core.
> - It should be mentioned in a document that foreign tables are not
> analyzed automatically because they are read-only.
OK. I'll revise.
> Regards,
Best regards,
Etsuro Fujita
From | Date | Subject | |
---|---|---|---|
Next Message | Pavan Deolasee | 2011-10-18 06:20:31 | Re: spinlocks on HP-UX |
Previous Message | Tatsuo Ishii | 2011-10-18 05:04:50 | Re: spinlocks on HP-UX |