Here is more detail on the patch. ---------------------------------------------------------------------------
Manfred Koizar wrote: > On Mon, 1 Dec 2003 00:02:54 -0500 (EST), Bruce Momjian > <[EMAIL PROTECTED]> wrote: > >Tom Lane wrote: > >> Bruce Momjian <[EMAIL PROTECTED]> writes: > >> >> And if it doesn't help index > >> >> creation speed, at least the resulting index has better correlation. > > ... which has been shown by the example in the original message: > > Result without patch: > > ctid > > ---------- > > (153,14) > > (306,23) > > (305,80) > > (152,91) > > (76,68) > > (38,34) > > (153,34) > > (305,50) > > (9,62) > > (305,40) > > (10 rows) > > > > Result with patch: > > ctid > > -------- > > (0,5) > > (0,10) > > (0,15) > > (0,20) > > (0,25) > > (0,30) > > (0,35) > > (0,40) > > (0,45) > > (0,50) > > (10 rows) > > And I think we all agree, that better index correlation leads to better > performance. > > >> I think this is a *very* dubious idea. It introduces a low-level > >> implementation dependency into our sort behavior > > The patch modifies the static function comparetup_index() in > tuplesort.c. > The comment above this function says > /* > * Routines specialized for IndexTuple case > * > * NOTE: actually, these are specialized for the btree case; [...] > */ > > comparetup_index() compares two IndexTuples. The structure > IndexTupleData consists basically of not much more than an ItemPointer, > and the patch is not much more than adding a comparison of two > ItemPointers. So how does the patch introduce a new low level > implementation dependency? > > >Roger --- patch removed. Thanks. > > Could we agree on only removing the first five a half lines of the > comment in the patch? > > Servus > Manfred > > ---------------------------(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 > -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
