Обсуждение: pgsql: Doc: clarify handling of duplicate elements in array containment

Doc: clarify handling of duplicate elements in array containment tests.

The array <@ and @> operators do not worry about duplicates: if every
member of array X matches some element of array Y, then X is contained
in Y, even if several members of X get matched to the same Y member.
This was not explicitly stated in the docs though, so improve matters.

Discussion: https://postgr.es/m/156614120484.1310.310161642239149585@wrigleys.postgresql.org

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/184b5fad00ace7009475221fcf12088e399f3249

Modified Files
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doc/src/sgml/func.sgml | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)