Andres Freund <and...@anarazel.de> writes:
> On June 28, 2018 4:18:36 PM PDT, Tom Lane <t...@sss.pgh.pa.us> wrote:
>> Also, is it really true that we don't support included expression
>> columns now? In what way would that not be a bug?
> I don't think IOS supports expression columns, right? Away from code for a
> bit, so can't check. If indeed true, there'd be little point in allowing it,
> right?
The point of ANALYZE on an expression column is that you can direct
ANALYZE to collect stats on that expression. This is potentially valuable
for rowcount estimation whether or not the planner notices that it can
fetch the expression value from the index, or chooses to do so even if it
did notice.
(In principle, CREATE STATISTICS might someday obsolete this use-case
for expression indexes, but it hasn't done so yet AFAIK.)
regards, tom lane
