Re: 9.6 phrase search distance specification

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От Ryan Pedela
Тема Re: 9.6 phrase search distance specification
Дата
Msg-id CACu89FTE1pRHuS7=R4i2OxC0zU5iK6ONH655acQr7KsGBnYfZA@mail.gmail.com
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Ответ на Re: 9.6 phrase search distance specification  (Ryan Pedela <rpedela@datalanche.com>)
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On Tue, Aug 9, 2016 at 12:59 PM, Ryan Pedela <rpedela@datalanche.com> wrote:


Thanks,

Ryan Pedela
Datalanche CEO, founder
www.datalanche.com

On Tue, Aug 9, 2016 at 11:58 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Bruce Momjian <bruce@momjian.us> writes:
> Does anyone know why the phrase distance "<3>" was changed from "at most
> three tokens away" to "exactly three tokens away"?

So that it would correctly support phraseto_tsquery's use of the operator
to represent omitted words (stopwords) in a phrase.

I think there's probably some use in also providing an operator that does
"at most this many tokens away", but Oleg/Teodor were evidently less
excited, because they didn't take the time to do it.

The thread where this change was discussed is

https://www.postgresql.org/message-id/flat/c19fcfec308e6ccd952cdde9e648b505%40mail.gmail.com

see particularly

https://www.postgresql.org/message-id/11252.1465422251%40sss.pgh.pa.us

 I would say that it is worth it to have a "phrase slop" operator (Apache Lucene terminology). Proximity search is extremely useful for improving relevance and phrase slop is one of the tools to achieve that.


Sorry for the position of my signature....

Ryan

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