table name "unnest" specified more than once

From: Guyren Howe <guyren(at)gmail(dot)com>
To: PG-General Mailing List <pgsql-general(at)postgresql(dot)org>
Subject: table name "unnest" specified more than once
Date: 2020-02-28 03:47:31
Message-ID: F1BCB309-7527-4A6A-9A04-8AA506AB4149@gmail.com
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# select
*
from
unnest(array[array['a', 'b'], array['c', 'c']]),
unnest(array[array['1', '2'], array['3', '4']]);
ERROR: 42712: table name "unnest" specified more than once

I’m trying to cross-join multiple two-dimensional arrays, expecting to retain the inner arrays. I’ve been trying for hours without luck; the ever-esoteric SQL syntax foils me at every turn.

It’s a shame I can’t get the unnest function not to just concatenate the inner arrays if I just put a bunch of them. This doesn’t strike me as optimal behavior.

For more context, I’m trying to make a system of functions to score a Texas Hold ‘Em game. So I have a card type consisting of a pair of suit and rank, and I’m tossing them about. The cross-join is so I can build all candidate hands for scoring. I’m trying to create a function I can call like this:

select
best_hands_with_river(
array[
c('H', 'K'),
c('D', 'A')
],
array[
c('C', '2'),
c('C', 'K'),
c('S', 'K'),
c('H', 'A'),
c('C', 'A')
])

Here, c is a function that constructs a card type. Card is a ROW(varchar, varchar).

So: how do I cross-join three identical arrays of my card type?

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