How are pg_operator and pg_type related with each other?

On Wed, Jan 15, 2014 at 11:08 PM, Felix.徐 <ygnhzeus@gmail.com> wrote:

Hi all,
I'm studying pg_statistic table and I find that column staop is related to
pg_operator, and different data types relate to different staop, but I don't
know where pgsql stores the mapping between pg_type and pg_operator, does
anyone have any idea about it? thanks!

Rather, different "kinds" of statistics are related to different
operators. So, "staop2" would refer to an operator suitable/applicable
for the statistics of kind "stakind2".

For example stakind2 for some attribute could be value "3" which
refers to statistic kind "histogram". In this case, staop2 for the
same attribute could refer to operator, say, "<" because this
particular operator could benefit from histogram distribution of
values. (off course, "<" may be overloaded for different types; but
point to take from this is that any "<" uses the statistic called
histogram.)

--
Amit Langote

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Hi Amit
I understand, I've read the source code of analyze.c and implemented a java
version.
Stakind1(most common values) indicates "=" operator and stakind2(histogram)
indicates "<" operator by default,
I'm wondering where I can find the corresponding operatorID of eq/lt for a
specific data type.
For example,
"=" operator for the type "varchar" is "texteq" and "<" operator for
varchar is "text_lt"
"=" operator for the type "int4" is "int4eq" and "<" operator for int4 is
"int4lt" etc.

And another question is that how to update or insert a column with type of
"anyarray", since I want to mock the statistic data of tables, the type of
stavalues in pg_statistic is anyarray, is there any way to manually modify
that column, by some kind of function or hook?
If I ran the query like:

UPDATE pg_statistic
SET stavalues2=array[1,2,8]
WHERE ...

Then I will get error 42804 indicates that the expected type is anyarry
but text[] is found in the query.

Thanks very much!

2014/1/15 Amit Langote <amitlangote09@gmail.com>

=?GB2312?B?RmVsaXgu0Ow=?= <ygnhzeus@gmail.com> writes:

I'm wondering where I can find the corresponding operatorID of eq/lt for a
specific data type.

The ones ANALYZE uses are the members of the default btree opclass for
the datatype. If there isn't one, it doesn't build a histogram.

And another question is that how to update or insert a column with type of
"anyarray", since I want to mock the statistic data of tables, the type of
stavalues in pg_statistic is anyarray, is there any way to manually modify
that column, by some kind of function or hook?

I don't believe that's possible from SQL; as you found out, the type
system won't allow it, and it'd be a security hole if it did (since
there wouldn't be any check that the data you store actually matches
the type of the column the pg_statistic row claims to be about).

regards, tom lane

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general