Re: Hash Indexes
От | Amit Kapila |
---|---|
Тема | Re: Hash Indexes |
Дата | |
Msg-id | CAA4eK1KXFJwHvPUOh4cwFtfeN6Z7ZDLz05GzyYsfw0ajYEC7gw@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: Hash Indexes (Robert Haas <robertmhaas@gmail.com>) |
Ответы |
Re: Hash Indexes
(Peter Geoghegan <pg@heroku.com>)
|
Список | pgsql-hackers |
<p dir="ltr">On 30-Sep-2016 6:24 AM, "Robert Haas" <<a href="mailto:robertmhaas@gmail.com">robertmhaas@gmail.com</a>>wrote:<br /> ><br /> > On Thu, Sep 29, 2016 at 8:29PM, Andres Freund <<a href="mailto:andres@anarazel.de">andres@anarazel.de</a>> wrote:<br /> > > On September29, 2016 5:28:00 PM PDT, Robert Haas <<a href="mailto:robertmhaas@gmail.com">robertmhaas@gmail.com</a>> wrote:<br/> > >>On Thu, Sep 29, 2016 at 8:16 PM, Andres Freund <<a href="mailto:andres@anarazel.de">andres@anarazel.de</a>><br/> > >>wrote:<br /> > >>>> Well, I,for one, find it frustrating. It seems pretty unhelpful to<br /> > >>>> bring this up only after the codehas already been written.<br /> > >>><br /> > >>> I brought this up in person at pgcon too.<br/> > >><br /> > >>To whom? In what context?<br /> > ><br /> > > Amit, over dinner.<br/> ><br /> > OK, well, I can't really comment on that, then, except to say that if<br /> > you waitedthree months to follow up on the mailing list, you probably<br /> > can't blame Amit if he thought that it was moreof a casual suggestion<br /> > than a serious objection. Maybe it was? I don't know.<br /> ><p dir="ltr">Bothof them have talked about hash indexes with me offline. Peter mentioned that it would be better to improvebtree rather than hash indexes. IIRC, Andres asked me mainly about what use cases I have in mind for hash indexesand then we do have some further discussion on the same thing where he was not convinced that there is any big usecase for hash indexes even though there may be some cases. In that discussion, as he is saying and I don't doubt him,he would have told me the alternative, but it was not apparent to me that he is expecting some sort of comparison.<pdir="ltr">What I got from both the discussions was a friendly gesture that it might be a better use of my time,if I work on some other problem. I really respect suggestions from both of them, but it was no where clear to me thatany one of them is expecting any comparison of other approach.<p dir="ltr">Considering, I have missed the real intentionof their suggestions, I think such a serious objection on any work should be discussed on list. To answer the actualobjection, I have already mentioned upthread that we can deduce from the current tests done by Jesper and Mithun thatthere are some cases where hash index will be better than hash-over-btree (tests done over integer columns). I thinkany discussion on whether we should consider not to improve current hash indexes is only meaningful if some one hasa code which can prove both theoretically and practically that it is better than hash indexes for all usages.<p dir="ltr">Note- excuse me for formatting of this email as I am on travel and using my phone.<p dir="ltr">With Regards, <br/> Amit Kapila.<br />
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