Re: RES: Trouble with regexp_matches
От | Adrian Klaver |
---|---|
Тема | Re: RES: Trouble with regexp_matches |
Дата | |
Msg-id | e473c5be-eced-dc77-7722-754b8f7623b3@aklaver.com обсуждение исходный текст |
Ответ на | RES: Trouble with regexp_matches (Edson Richter <edsonrichter@hotmail.com>) |
Список | pgsql-general |
On 11/05/2016 11:56 AM, Edson Richter wrote: >> -----Mensagem original----- >> De: Adrian Klaver [mailto:adrian.klaver@aklaver.com] >> Enviada em: sábado, 5 de novembro de 2016 15:13 >> Para: Edson Richter <edsonrichter@hotmail.com>; pgsql- >> general@postgresql.org >> Assunto: Re: [GENERAL] Trouble with regexp_matches >> >> On 11/05/2016 10:01 AM, Edson Richter wrote: >>> Dear list, >>> >>> >>> >>> Version string PostgreSQL 9.4.10 on x86_64-unknown-linux-gnu, >>> compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-4), 64-bit >>> >>> >>> >>> I’m running the query below, and it is limiting results as if >>> “regexp_matches” being in where clause. >>> >>> IMHO, it is wrong: in case there is no match, shall return null or >>> empty array – not remove the result from the set!!! >>> >>> >>> >>> Is this a collateral effect of using regexp_matches in columns? >>> >>> If yes, shall not this information be BOLD RED FLASHING in >>> documentation (or it is already, and some kind sould would point me >> where)? >> >> https://www.postgresql.org/docs/9.4/static/functions-matching.html > > > I see - I always believed that this page was related to WHERE clause or using functions in the PostgreSQL way (which is,in your turn, a alternative to "from" syntax) - not for the select clause. > But now that you mention it, and re-reading all the information, I can understand the implications. > > Nevertheless, would be nice to put a huge warning at the "String functions" page about this behavior... Well the above page is pointed to in the string functions section: https://www.postgresql.org/docs/9.4/static/functions-string.html "regexp_matches(string text, pattern text [, flags text]) setof text[] Return all captured substrings resulting from matching a POSIX regular expression against the string. See Section 9.7.3 for more information." Where 'Section 9.7.3' is a link to it. Not sure if that counts as a warning though:) > >> >> "It is possible to force regexp_matches() to always return one row by using a >> sub-select; this is particularly useful in a SELECT target list when you want all >> rows returned, even non-matching ones: >> >> SELECT col1, (SELECT regexp_matches(col2, '(bar)(beque)')) FROM tab; " >> > > Thanks, this worked - as well removing the "regexp_matches" and using "SUBSTRING( text FROM pattern)". > > > I really appreciate your help. > > > Kind regards, > > Edson Richter > > >> >> >>> >>> >>> >>> -- First query (that is limiting results) >>> --------------------------------------------------------------------- >>> >>> select codigoocorrencia, datahoraocorrencia, datahoraimportacao, >>> observacao, regexp_matches(observacao, '\d\d/\d\d/\d\d\d\d') >>> >>> from batchloteocorrencia >>> >>> where codigoocorrencia = '091' >>> >>> and observacao is not null >>> >>> order by datahoraimportacao DESC >>> >>> >>> >>> Total results = 59 >>> >>> >>> >>> --Second query (that is not limiting results, as I did >>> expect)--------------------------------------------------------------- >>> ---- >>> >>> select codigoocorrencia, datahoraocorrencia, datahoraimportacao, >>> observacao >>> >>> from batchloteocorrencia >>> >>> where codigoocorrencia = '091' >>> >>> and observacao is not null >>> >>> order by datahoraimportacao DESC >>> >>> >>> >>> Total results = 3826 >>> >>> >>> >>> >>> >>> Why is that? >>> >>> >>> >>> Regards, >>> >>> >>> >>> Edson Richter >>> >> >> >> -- >> Adrian Klaver >> adrian.klaver@aklaver.com > > -- Adrian Klaver adrian.klaver@aklaver.com
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