Re: How to specify/mock the statistic data of tables in PostgreSQL

=?GB2312?B?RmVsaXgu0Ow=?= <ygnhzeus@gmail.com> writes:
> //line 194 : In a "most common values" slot, staop is the OID of the "="
> operator used to decide whether values are the same or not.
> //line 206 : A "histogram" slot describes the distribution of scalar data.
>  staop is the OID of the "<" operator that describes the sort ordering.

> I don't understand the function of staop here, how is it used in optimizer,

In principle a data type could have more than one sort ordering, and if
we were to collect stats according to multiple orderings, staop would be
needed to identify which ordering a particular set of statistics was
created with.  That flexibility isn't being used right now, at least not
by any built-in code.  There are types with more than one ordering (more
than one btree opclass), but ANALYZE only collects stats for the default
btree opclass.

            regards, tom lane