On 5/25/17 12:30, Konstantin Knizhnik wrote: > Functions like (info->>'name') are named "surjective" ni mathematics.
A surjective function is one where each value in the output type can be obtained by some input value. That's not what you are after here. The behavior you are describing is a not-injective function. I think you are right that in practice most functions are not injective. But I think there is still quite some difference between a function like the one you showed that selects a component from a composite data structure and, for example, round(), where in practice any update is likely to change the result of the function. -- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
