Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> Tom Lane wrote:
>> Insert a sort order column into pg_enum, and rearrange the values in
>> that whenever the user wants to add a new value in a particular place.
>> You give up cheap comparisons in exchange for flexibility. I think lots
>> of people would accept that tradeoff, especially if they could make it
> But I'm not happy about giving up cheap comparison.
I don't think it would be all that bad. We could teach typcache.c to
cache the ordering data for any type that's in active use. It'd
certainly be a lot more expensive than OID comparison, but perhaps not
worse than NUMERIC comparisons.
> And how would it be per data-type?
Well, there'd be two kinds of enums, just as you were saying before.
I'm not sure how we'd expose that to users exactly, or whether there
could be provisions for switching a type's behavior after creation.
regards, tom lane
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