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From: Tom Lane <tgl@sss.pgh.pa.us>
To: AlexK <alkuzo@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: How to unnest an array with element indexes
Date: Wed, 19 Feb 2014 15:16:10 -0500
Message-ID: <13954.1392840970@sss.pgh.pa.us> (raw)
In-Reply-To: <1392839868185-5792774.post@n5.nabble.com>
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AlexK <alkuzo@gmail.com> writes:
> David,
> The array stores a time series of values for consecutive days. All I need is
> take an array such as ARRAY[1.1,1.2] and return to the client the following

> series_start_date + (array_index-1), array_value

> Based on what you are saying, the following should do it:

> with pivoted_array AS(
> select unnest(ARRAY[1.1,1.2])
> ),
> indexed_array AS(
> select 
>         row_number()OVER() AS element_index, 
>         unnest as element_value
> from pivoted_array)
> SELECT 
>         (DATE '2014-02-19' + INTERVAL '1d'*(element_index-1)) AS
> series_date, 
>         element_value AS series_value
> FROM indexed_array

That sure seems like the hard way, as well as uncertainly correct.
I'd use something involving generate_subscripts(), for example if
tab.arraycol is the source of the array data:

select i, arraycol[i] from tab, lateral generate_subscripts(arraycol, 1) as i;

If you're using a version of Postgres that doesn't have LATERAL, it's
a bit more complicated but you can do it with a subquery.

			regards, tom lane


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