Re: Using regular expressions in LIKE
От | Nick Barr |
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Тема | Re: Using regular expressions in LIKE |
Дата | |
Msg-id | 8F4A22E017460A458DB7BBAB65CA6AE502AA48@openmanage обсуждение исходный текст |
Ответ на | Using regular expressions in LIKE (Együd Csaba <csegyud@vnet.hu>) |
Ответы |
Re: Using regular expressions in LIKE
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Список | pgsql-general |
> -----Original Message----- > From: pgsql-general-owner@postgresql.org [mailto:pgsql-general- > owner@postgresql.org] On Behalf Of Patrick Welche > Sent: 15 January 2004 12:09 > To: Nick Barr > Cc: csegyud@vnet.hu; terry@ashtonwoodshomes.com; 'Pgsql- > General@Postgresql.Org (E-mail)' > Subject: Re: [GENERAL] Using regular expressions in LIKE > > On Thu, Jan 15, 2004 at 09:05:35AM -0000, Nick Barr wrote: > > If the ^ was not there then it could theoretically match anywhere in the > > string. In this particular case the regular expression will probably > > match at the beginning of the string anyway, so it is not really > > necessary. I prefer to put that sort of thing in to make it clear to the > > programmer what is going on. > > Isn't there also a performance benefit as you can use an index if you > say "this definitely starts at the beginning" with the '^'? That is what I was thinking, which is the other reason why I put it in. This is certainly the case with queries that use the LIKE operator, for example: where adate like 'random%'; This is only the case with the default locale I believe. I have no idea when it comes to regexs though and specifically the ~ operator. Could someone more knowledgeable about this stuff reply? Nick
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