Re: [HACKERS] lztext and parser
От | Karel Zak - Zakkr |
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Тема | Re: [HACKERS] lztext and parser |
Дата | |
Msg-id | Pine.LNX.3.96.991125122326.16693B-100000@ara.zf.jcu.cz обсуждение исходный текст |
Ответ на | lztext and parser (wieck@debis.com (Jan Wieck)) |
Ответы |
Re: [HACKERS] lztext and parser
(wieck@debis.com (Jan Wieck))
|
Список | pgsql-hackers |
On Thu, 25 Nov 1999, Jan Wieck wrote: > Hi, > > I'm hacking in the operator functions for the lztext type and > have a little question. Hi, I see your the lztext/pg_compress in CVS and it is *very* nice, and I have a little comment. > With the generic per-byte decompressor I added, it would be > very easy to produce functions like It's very good if compression routines support data stream. Suppose you add the pre-byte compressor? Reasoning: What is fastly - (1) a standard data I/O reading or (2) a compressed data I/O reading and decompressit (fast CPU vs. slowly I/O)? IMHO if (2) is fastly is prabably good for something data use second way. But I don't know where use this way in PgSQL :-) > too. Comparision between lztext and text does already work > because there are lztext->text and vice versa functions > available and the parser automatically typecasts. > > So would it be a win or a dead end street to provide those > functions? Does it look for a direct comparision function > allways first? Then it would be, because it would never > choose to compress the text item and then compare two > lztext's (what would be terrible). > In the lztext_eq(lztext *lz1, lztext *lz2) you use lztext_cmp(). I'm not sure if it is good, because you must decompress fistly, but you don't need information about '<' or '>', you need '=' only. Why you not use memcmp() (or other method) for this, and comparate this without decompression? Two equal string is equal in a compressed form, or not? IMHO in some routines (datetime) in PgSQL I saw internal cache, what add this to the lztext_cmp(), and not decompress all in each time? All in this letter is comments and suggestions, you can always remove this letter to /dev/null :-) Karel ------------------------------------------------------------------------------ Karel Zak <zakkr@zf.jcu.cz> http://home.zf.jcu.cz/~zakkr/ Docs: http://docs.linux.cz (big docs archive) Kim Project: http://home.zf.jcu.cz/~zakkr/kim/ (process manager) FTP: ftp://ftp2.zf.jcu.cz/users/zakkr/ (C/ncurses/PgSQL) ------------------------------------------------------------------------------
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