We have window function version of first_value(),
but aggregate version looks useful to write queries something like:
=# CREATE TABLE obj (id integer, pos point);
=# SELECT X.id, first_value(Y.id ORDER BY X.pos <-> Y.pos) AS neighbor FROM obj X, obj Y GROUP BY X.id;
Is it reasonable? Or, do we have alternative ways for the same purpose?
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Itagaki Takahiro
