Re: Immutable way to cast timestamp TEXT to DATE? (for index)

From: Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
To: Ken Tanzer <ken(dot)tanzer(at)gmail(dot)com>, PG-General Mailing List <pgsql-general(at)postgresql(dot)org>
Subject: Re: Immutable way to cast timestamp TEXT to DATE? (for index)
Date: 2019-01-04 22:27:02
Message-ID: 85d0c08f-64ea-b980-a6cd-425b97159c8d@aklaver.com
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On 1/4/19 2:21 PM, Ken Tanzer wrote:
> Hi.  I've got a text field in a table that holds this style of timestamp:
>
> 2014-10-23T00:00:00
>
> I'd like to be able to create an index on the date portion of this field
> (as a date), because I have lots of queries that are searching for
> particular dates or ranges.
>
> I've tried various ways of getting to a date (::date, LEFT(x,10)::date,
> etc.), but all of them throw the error "functions in index expression
> must be marked IMMUTABLE."

?:
'2014-10-23T00:00:00'::timestamp

Can you also show the actual index expression?

>
> Is there any way, hacky or otherwise, people know of to do this?  Thanks
> in advance.
>
> Ken
>
>
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Adrian Klaver
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