| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Small improvement to parallel query docs |
| Date: | 2017-02-13 00:16:13 |
| Message-ID: | CAKJS1f81fob-M6RJyTVv3SCasxMuQpj37ReNOJ=tprhwd7hAVg@mail.gmail.com |
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| Lists: | pgsql-hackers |
Tomas Vondra pointed out to me that there's an error in parallel.sgml
which confuses the inner and outer sides of the join.
I've attached a patch which fixes this, although I think I'm still
missing the point to text's explanation of why Merge Join is not
included due to it having to sort the inner side in each worker. Hash
join must build a hash table for each worker, so why is that OK by
sorting is not?
Anyway, I've attached a patch which fixes the outer/inner confusion
and cleans up a couple of other grammar mistakes and an omissions
regarding DISTINCT and ORDER BY not being supported in parallel
aggregate. I ended up rewriting a section too which was explaining
parallel aggregate, which I personally believe is a bit more clear to
read, but someone else may think otherwise.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
| Attachment | Content-Type | Size |
|---|---|---|
| parallel_doc_fixes.patch | application/octet-stream | 4.9 KB |
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