Folks,
(the below was already discussed on IRC)
Leaving names aside on this patch, I'm wondering about a piece of
functionality I have with the current unnest() and with the
unnest_ordinality()[1] extension: namely, the ability to unnest several
arrays "in parallel" by using unnest() in the target list.
For example, given the table:
lotsarrays (
id serial PK,
arr1 int[],
arr2 numeric[],
arr3 boolean[]
)
I can currently do:
SELECT id,
unnest(arr1) as arr1,
unnest(arr2) as arr2,
unnest(arr3) as arr3
FROM lotsarrays;
... and if arr1, 2 and 3 are exactly the same length, this creates a
coordinated dataset. I can even use the unnest_ordinality() extension
function to get the ordinality of this combined dataset:
SELECT id,
(unnest_ordinality(arr1)).element_number as array_index,
unnest(arr1) as arr1,
unnest(arr2) as arr2,
unnest(arr3) as arr3
FROM lotsarrays;
There are reasons why this will be complicated to implement WITH
ORDINALITY; DF, Andrew and I discussed them on IRC. So allowing WITH
ORDINALITY in the target list is a TODO, either for later in 9.4
development, or for 9.5.
So, this isn't stopping the patch; I just want a TODO for "implement
WITH ORDINALITY in the target list for SRFs".
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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