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 20:26:54
Message-ID: CAFj8pRCdGO_QX0SZLqgqEHMKfouyFbBCxi4FUS+VgGUht+9tgQ@mail.gmail.com
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Hello

here is a initial version of row_to_array function - transform any row to
array in format proposed by Andrew.

Regards

Pavel

2015-01-27 19:58 GMT+01:00 Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:

> 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
row_to_array-PoC.patch text/x-patch 5.5 KB

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