Doc: add example of type resolution in nested UNIONs

Enterprise / PostgreSQL - Tom Lane [sss.pgh.pa.us] - 25 March 2018 20:15 UTC

Section 10.5 didn't say explicitly that multiple UNIONs are resolved pairwise. Since the resolution algorithm is described as taking any number of inputs, readers might well think that a query like "select x union select y union select z" would be resolved by considering x, y, and z in one resolution step. But that's not what happens (and I think that behavior is per SQL spec). Add an example clarifying this point.

Per bug #15129 from Philippe Beaudoin.

Discussion: https://postgr.es/m/152196085023.32649.9916472370480121694@wrigleys.postgresql.org

c515ff8d0a Doc: add example of type resolution in nested UNIONs.
doc/src/sgml/typeconv.sgml | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)

Upstream: git.postgresql.org


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