Re: [HACKERS] [PERFORM] How to read query plan
=?windows-1250?Q?Miroslav_=8Aulc?= <[EMAIL PROTECTED]> writes: > Tom Lane wrote: >> Actually, we already had a pending patch (from Atsushi Ogawa) that >> eliminates that particular O(N^2) behavior in another way. After >> applying it, I get about a factor-of-4 reduction in the runtime for >> Miroslav's example. >> > Is there a chance we will see this patch in the 8.0.2 release? No. We are not in the habit of making non-bug-fix changes in stable branches. Ogawa's patch is in CVS for 8.1. regards, tom lane ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] [PERFORM] How to read query plan
Tom Lane wrote: I wrote: Since ExecProject operations within a nest of joins are going to be dealing entirely with Vars, I wonder if we couldn't speed matters up by having a short-circuit case for a projection that is only Vars. Essentially it would be a lot like execJunk.c, except able to cope with two input tuples. Using heap_deformtuple instead of retail extraction of fields would eliminate the O(N^2) penalty for wide tuples. Actually, we already had a pending patch (from Atsushi Ogawa) that eliminates that particular O(N^2) behavior in another way. After applying it, I get about a factor-of-4 reduction in the runtime for Miroslav's example. Is there a chance we will see this patch in the 8.0.2 release? And when can we expect this release? ExecEvalVar and associated routines are still a pretty good fraction of the runtime, so it might still be worth doing something like the above, but it'd probably be just a marginal win instead of a big win. regards, tom lane Miroslav begin:vcard fn;quoted-printable:Miroslav =C5=A0ulc n;quoted-printable:=C5=A0ulc;Miroslav org:StartNet s.r.o. adr;quoted-printable;quoted-printable:;;Vrchlick=C3=A9ho 161/5;Praha 5;;150 00;=C4=8Cesk=C3=A1 republika email;internet:[EMAIL PROTECTED] title:CEO tel;work:+420 257 225 602 tel;cell:+420 603 711 413 x-mozilla-html:TRUE url:http://www.startnet.cz version:2.1 end:vcard ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
Re: [HACKERS] [PERFORM] How to read query plan
I wrote: > Since ExecProject operations within a nest of joins are going to be > dealing entirely with Vars, I wonder if we couldn't speed matters up > by having a short-circuit case for a projection that is only Vars. > Essentially it would be a lot like execJunk.c, except able to cope > with two input tuples. Using heap_deformtuple instead of retail > extraction of fields would eliminate the O(N^2) penalty for wide tuples. Actually, we already had a pending patch (from Atsushi Ogawa) that eliminates that particular O(N^2) behavior in another way. After applying it, I get about a factor-of-4 reduction in the runtime for Miroslav's example. ExecEvalVar and associated routines are still a pretty good fraction of the runtime, so it might still be worth doing something like the above, but it'd probably be just a marginal win instead of a big win. regards, tom lane ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
