Re: hstore each() function - returned order??

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>
Cc: Brent Wood <Brent(dot)Wood(at)niwa(dot)co(dot)nz>, "pgsql-general(at)lists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org>
Subject: Re: hstore each() function - returned order??
Date: 2021-03-12 14:52:13
Message-ID: 2439589.1615560733@sss.pgh.pa.us
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"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> On Fri, Mar 12, 2021 at 3:18 AM Brent Wood <Brent(dot)Wood(at)niwa(dot)co(dot)nz> wrote:
>> Is this what you mean?
>>
>> select measurement_key,
>> value
>> from t_reading_hstore,
>> lateral ((EACH(value)).key as measurement_key,
>> lateral ((EACH(value)).value as value;

> The definition of "each" shows that it returns a record type. That whole
> type can be considered a table and referenced in the select list.

Yeah. To my mind, the main point here is to run each() just once per
t_reading_hstore row, not twice. So something like

SELECT e.key, e.value FROM t_reading_hstore AS t, each(t.value) AS e;

(Writing LATERAL is optional.)

regards, tom lane

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