BTW, having both key_is_null and key_is_not_null output args to convey a
single bit of info is a bit lame. I'm removing it. We could do the
same with a single boolean, since the return value already indicates
it's a matching IS [NOT] NULL clause; we only need to indicate whether
the NOT is present.
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Álvaro Herrera https://www.2ndQuadrant.com/
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