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From: Ildus Kurbangaliev <i.kurbangaliev@postgrespro.ru>
To: Emre Hasegeli <emre@hasegeli.com>
Cc: Teodor Sigaev <teodor@sigaev.ru>
Cc: Alexander Korotkov <a.korotkov@postgrespro.ru>
Cc: Arthur Zakirov <a.zakirov@postgrespro.ru>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Prefix operator for text and spgist support
Date: Mon, 16 Apr 2018 15:50:36 +0300
Message-ID: <20180416155036.36070396@wp.localdomain> (raw)
In-Reply-To: <CAE2gYzw0i2ejZrS5y2-PVbe7qBE3deNAC1dLaFT75hNEgxZRUA@mail.gmail.com>
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	<20180219120650.GA2142@zakirov.localdomain>
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	<20180306162720.GA21305@zakirov.localdomain>
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	<e71b4911-7cd0-fd6f-29c8-95225c3beb11@sigaev.ru>
	<CAPpHfduzc_6G0yqJfji7NxfJ6ML5nODDx6+A15GNis5zgRho+Q@mail.gmail.com>
	<20180329143634.33c53348@wp.localdomain>
	<03300255-cff2-b508-50f4-f00cca0a57a1@sigaev.ru>
	<CAE2gYzw0i2ejZrS5y2-PVbe7qBE3deNAC1dLaFT75hNEgxZRUA@mail.gmail.com>

On Mon, 16 Apr 2018 12:45:23 +0200
Emre Hasegeli <emre@hasegeli.com> wrote:

> > Thank you, pushed with some editorization and renaming
> > text_startswith to starts_with  
> 
> I am sorry for not noticing this before, but what is the point of this
> operator?  It seems to me we are only making the prefix searching
> business, which is already complicated, more complicated.

Hi.

> 
> Also, the new operator is not documented on SQL String Functions and
> Operators table.  It is not supported by btree text_pattern_ops or
> btree indexes with COLLATE "C".  It is not defined for "citext", so
> people would get wrong results.  It doesn't use pg_trgm indexes
> whereas LIKE can.

It is mentioned in documentation, look for "starts_with" function.
Currently it's working with spgist indexes which fact is pointed out in
the documentation too. I was going to add btree support but it would
require a new strategy so it will be matter of another patch. I think
this operator could be used in LIKE instead of current weird comparison
operators.

-- 
---
Ildus Kurbangaliev
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company




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