Thread: How to make operator class?
when create indexes, use operator class like this. CREATE INDEX idx_name ON tbl_name (col_name [operator class]); so, i made an operator. but i think that it is different operator class because operator class doesn't work at all. then, how to make operator class? ================================================== ================================================== 우리 인터넷, Daum 평생 쓰는 무료 E-mail 주소 한메일넷 지구촌 한글 검색서비스 Daum FIREBALL http://www.daum.net
"Kim Yunhan" <spbear@hanmail.net> writes: > then, how to make operator class? See the Programmer's Guide, particularly http://www.postgresql.org/devel-corner/docs/postgres/xindex.htm If this is a followup to your previous question about making a reverse-order index, you'll need to start by making a support function that delivers the reverse (negative) of what the existing btree comparison function for the datatype does (see btint4cmp and friends). The remaining operators to comprise the opclass are the same ones that exist already, you just need to swap their positions (use '<' for '>' etc). Good luck! regards, tom lane
Tom, > > Hmmm .... thinking about it logically, shouldn't the database engine be > > able to use an index on a single column either backwards or forwards? > > Sure, but he wanted a sort with the first column in ascending order and > the second in descending order. You can't get that by scanning an index > that has both columns in the same order... Aha. I see the problem. My approach would be to use two seperate indexes, but maybe that's not sophisticated enough :-) And, Tom, you're working too hard again. It's Saturday. Go home. -Josh Berkus (Who is home, just VPN'ing into my office). -- ______AGLIO DATABASE SOLUTIONS___________________________ Josh Berkus Complete informationtechnology josh@agliodbs.com and data management solutions (415) 565-7293 for law firms, small businesses fax 621-2533 and non-profit organizations. San Francisco