Re: INSERT ... ON CONFLICT UPDATE/IGNORE 4.0, parser/executor stuff
От | Andres Freund |
---|---|
Тема | Re: INSERT ... ON CONFLICT UPDATE/IGNORE 4.0, parser/executor stuff |
Дата | |
Msg-id | 20150428103845.GC19123@awork2.anarazel.de обсуждение исходный текст |
Ответ на | Re: INSERT ... ON CONFLICT UPDATE/IGNORE 4.0, parser/executor stuff (Andres Freund <andres@anarazel.de>) |
Ответы |
Re: INSERT ... ON CONFLICT UPDATE/IGNORE 4.0,
parser/executor stuff
(Peter Geoghegan <pg@heroku.com>)
|
Список | pgsql-hackers |
On 2015-04-27 23:52:58 +0200, Andres Freund wrote: > On 2015-04-27 16:28:49 +0200, Andres Freund wrote: > > On 2015-04-26 18:02:06 -0700, Peter Geoghegan wrote: > > > * So far, there has been a lack of scrutiny about what the patch does > > > in the rewriter (in particular, to support the EXCLUDED.* pseudo-alias > > > expression) and optimizer (the whole concept of an "auxiliary" > > > query/plan that share a target RTE, and later target ResultRelation). > > > If someone took a close look at that, it would be most helpful. > > > ruleutils.c is also modified for the benefit of EXPLAIN output. This > > > all applies only to the ON CONFLICT UPDATE patch. A committer could > > > push out the IGNORE patch before this was 100% firm. > > > > I'm far from an expert on the relevant regions; but I'm starting to look > > nonetheless. I have to say that on a preliminary look it looks more > > complicated than it has to. > > So, I'm looking. And I've a few questions: > * Why do we need to spread knowledge about speculative inserts that wide? > It's now in 1) Query, 2) ParseState 3) ModifyTable 4) InsertStmt. That > seems a bit wide - and as far as I see not really necessary. That e.g. > transformUpdateStmt() has if (!pstate->p_is_speculative) blocks seems > wrong. > > * afaics 'auxiliary query' isn't something we have under that > name. This isn't really different to what wCTEs do, so I don't think > we need this term here. > > * You refer to 'join like syntax' in a couple places. I don't really see > the current syntax being that join like? Is that just a different > perception of terminology or is that just remnants of earlier > approaches? > > * I am rather unconvinced we need the whole 'ExcludedVar' mechanism. I > don't really see why we need it at all? Can't we 'just' make those > plain vars referring to the normal targetlist "entry"? I feel like I'm > missing something here. > > * The whole dealing with the update clause doesn't seem super > clean. I'm not sure yet how to do it nicer though :( The more I look at approach taken in the executor, the less I like it. I think the fundamental structural problem is that you've chosen to represent the ON CONFLICT UPDATE part as fully separate plan tree node; planned nearly like a normal UPDATE. But it really isn't. That's what then requires you to coordinate knowedge around with p_is_speculative, have these auxiliary trees, have update nodes without a relation, and other similar things. My feeling is that this will look much less ugly if there's simply no UpdateStmt built. I mean, all we need is the target list and the where clause. As far as I can see so far that'll get rid of a lot of structural uglyness. There'll still be some more localized stuff, but I don't think it'll be that bad. I'm actually even wondering if it'd not better off *not* to reuse ExecUpdate(), but that's essentially a separate concern. I'll try to rejigger things roughly in that directions. If you haven't heard of me in three days, call the police. Greetings, Andres Freund
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