Re: Yet another LIKE-indexing scheme
Bruce Momjian <pgman@candle.pha.pa.us>
From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Erich Stamberger <eberger@gewi.kfunigraz.ac.at>, pgsql-hackers@postgreSQL.org
Date: 2000-10-16T16:53:36Z
Lists: pgsql-hackers
Any status on this? > Erich Stamberger <eberger@gewi.kfunigraz.ac.at> writes: > >> Our existing code fails because it generates WHERE name >= 'Czec' AND > >> name < 'Czed'; it will therefore not find names beginning 'Czech' > >> because those are in another part of the index, between 'Czeh' and > >> 'Czei'. But WHERE name >= 'Cze' AND name < 'Czf' would work. > > > The Problem is: What tells us, that it is 'f' which sorts > > after 'e' in that locale? > > We keep trying until we find a character that *does* sort after 'e'. > I did say I was assuming that people had read the previous discussion > and knew what the existing approach was ;-) > > However I've since thought of a different counterexample: if the LIKE > pattern is 'Czech%' and we strip off the 'h', we lose since we'll be > looking between 'Czec' and 'Czed' but the desired strings are in the > index between 'Czeh' and 'Czei'. Back to the drawing board... > > regards, tom lane > -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026