Re: proposal: row_to_array function

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: proposal: row_to_array function
Date: 2015-01-27 18:58:42
Message-ID: CAFj8pRD7=xahZJDNnb2HxF3g1M7hSegiQa-H=gLtfP6d7+daGg@mail.gmail.com
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Hi

2015-01-27 11:41 GMT+01:00 Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:

>
>
> 2015-01-26 21:44 GMT+01:00 Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>:
>
>> On 1/25/15 4:23 AM, Pavel Stehule wrote:
>>
>>>
>>> I tested a concept iteration over array in format [key1, value1, key2,
>>> value2, .. ] - what is nice, it works for [[key1,value1],[key2, value2],
>>> ...] too
>>>
>>> It is only a few lines more to current code, and this change doesn't
>>> break a compatibility.
>>>
>>> Do you think, so this patch is acceptable?
>>>
>>> Ideas, comments?
>>>
>>
>> Aside from fixing the comments... I think this needs more tests on corner
>> cases. For example, what happens when you do
>>
>> foreach a, b, c in array(array(1,2),array(3,4)) ?
>>
>
> it is relative simple behave -- empty values are NULL
>
> array(1,2),array(3,4) -- do you think ARRAY[[1,2],[3,4]] is effectively
> ARRAY[1,2,3,4]
>
>
>>
>> Or the opposite case of
>>
>> foreach a,b in array(array(1,2,3))
>>
>> Also, what about:
>>
>> foreach a,b in '{{{1,2},{3,4}},{{5,6},{7,8}}}'::int[] ?
>
>
>
> postgres=# select array(select
> unnest('{{{1,2},{3,4}},{{5,6},{7,8}}}'::int[]));
> array
> -------------------
> {1,2,3,4,5,6,7,8}
> (1 row)
>
> so it generate pairs {1,2}{3,4},{5,6},{7,8}
>

I fixed situation when array has not enough elements.

More tests, simple doc

Regards

Pavel

>
> Regards
>
> Pavel Stehule
>
>
>> --
>> Jim Nasby, Data Architect, Blue Treble Consulting
>> Data in Trouble? Get it in Treble! http://BlueTreble.com
>>
>
>

Attachment Content-Type Size
foreach-key-value-01.patch text/x-patch 8.2 KB

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