Views dependency

"Shoaib Mir" <shoaibmir@gmail.com> writes:

Now is there any query or any catalog table available by which I can get to
know the dependency (names of views on which v2 depends) for view v2?

If you get up-close-n-personal with pg_depend you can determine that.

regards, tom lane

Shoaib Mir escribi�:

Suppose I have a view:

create view v1 as select * from t1;

and another view as:

create view v2 as select * from v1;

Now is there any query or any catalog table available by which I can get to
know the dependency (names of views on which v2 depends) for view v2?

Yes, pg_depend has a row for v2 to indicate dependency on the pg_rewrite
row, which in turn has an entry to indicate dependency on v1.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

I can see the following in pg_depend:

For view v1:

classid | objid | objsubid | refclassid | refobjid | refobjsubid | deptype
---------+--------+----------+------------+----------+-------------+---------
2618 | 153523 | 0 | 1259 | 153521 | 0 | n
2618 | 153523 | 0 | 1259 | 153521 | 0 | i
1247 | 153522 | 0 | 1259 | 153521 | 0 | i
2618 | 153526 | 0 | 1259 | 153521 | 1 | n
2618 | 153526 | 0 | 1259 | 153521 | 2 | n
2618 | 153526 | 0 | 1259 | 153521 | 3 | n
2618 | 153526 | 0 | 1259 | 153521 | 4 | n
2618 | 153526 | 0 | 1259 | 153521 | 5 | n
2618 | 153526 | 0 | 1259 | 153521 | 6 | n
2618 | 153526 | 0 | 1259 | 153521 | 7 | n
2618 | 153526 | 0 | 1259 | 153521 | 8 | n

For v2:

classid | objid | objsubid | refclassid | refobjid | refobjsubid | deptype
---------+--------+----------+------------+----------+-------------+---------
2618 | 153526 | 0 | 1259 | 153524 | 0 | n
2618 | 153526 | 0 | 1259 | 153524 | 0 | i
1247 | 153525 | 0 | 1259 | 153524 | 0 | i

and in pg_rewrite I got two entries for v1 and v2 as:

rulename | ev_class | ev_attr | ev_type | is_instead | ev_qual
---------+--------+----------+------------+----------+-------------+---------
_RETURN | 153521 | -1 | 1 | t | <>
_RETURN | 153524 | -1 | 1 | t | <>

Right now confused on how do I actually get the dependent views from this
kind of output... any ideas?

--
Shoaib Mir
EnterpriseDB (www.enterprisedb.com)

Used a different way but finally got my dependent views and table info for a
specific view. Here is how I did it:

==========================================
declare
pos integer;
wh integer;
tot integer;
diff integer;
outp varchar;
viewn varchar;
begin
viewn := 'v2';
select position('FROM' in definition) from pg_views where viewname =
viewn into pos;
select position('WHERE' in definition) from pg_views where viewname =
viewn into wh;
select length(definition) from pg_views where viewname = viewn into tot;

    diff := tot - pos;

IF wh = 0 THEN
select replace(substr(definition, pos+5, diff), ';', '') from
pg_views where viewname = viewn into outp;
END IF;

IF wh != 0 THEN
diff := wh - pos;
diff := diff - 6;
select substr(definition, pos+5, diff) from pg_views where viewname
= viewn into outp;
END IF;
end;
=====================================

--
Shoaib Mir
EnterpriseDB (www.enterprisedb.com)