Updates on Views?

On 21 Mar 2001, Konstantinos Agouros wrote:

Hi,

are views in PG read-only or is this possible?

You can make updatable views by making the appropriate rules
on the view for handling insert/update/delete (whatever
you want).

Stephan Szabo <sszabo@megazone23.bigpanda.com> wrote:

You can make updatable views by making the appropriate rules on the view
for handling insert/update/delete (whatever you want).

An example can be found in Bruce Momjian's book in the section on Rules
(http://www.postgresql.org/docs/aw_pgsql_book/node150.html).

Ray
--
[Open Source] is the finest expression of the free market. Ideas are
encouraged to proliferate and the best thinking wins. By contrast, most
corporations today operate in a central planning straitjacket.
http://www.thestandard.com/article/display/0,1151,15772,00.html

In <Pine.BSF.4.21.0103212025030.38659-100000@megazone23.bigpanda.com> sszabo@megazone23.bigpanda.com (Stephan Szabo) writes:

On 21 Mar 2001, Konstantinos Agouros wrote:

Hi,

are views in PG read-only or is this possible?

You can make updatable views by making the appropriate rules
on the view for handling insert/update/delete (whatever
you want).

Could You give me a hint on where to read up on this?

Konstantin

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Dipl-Inf. Konstantin Agouros aka Elwood Blues. Internet: elwood@agouros.de
Otkerstr. 28, 81547 Muenchen, Germany. Tel +49 89 69370185
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On Thu, Mar 22, 2001 at 09:48:43PM +0100, Konstantinos Agouros wrote:

In <Pine.BSF.4.21.0103212025030.38659-100000@megazone23.bigpanda.com> sszabo@megazone23.bigpanda.com (Stephan Szabo) writes:

On 21 Mar 2001, Konstantinos Agouros wrote:

are views in PG read-only or is this possible?

views are read-only -- but interestingly, a view is actually an
empty table with interference-running rules attached. you can
overlay your own 'do instead' rules to effect various
behind-the-scenes inserts and updates...

You can make updatable views by making the appropriate rules
on the view for handling insert/update/delete (whatever
you want).

Could You give me a hint on where to read up on this?

on my debian system it's mentioned in the postgresql-doc package
at...

% grep -rl INSTEAD /usr/share/doc/postgresql-doc/html
/usr/share/doc/postgresql-doc/html/programmer/rules1139.htm
/usr/share/doc/postgresql-doc/html/programmer/rules978.htm
/usr/share/doc/postgresql-doc/html/user/sql-createrule.htm
/usr/share/doc/postgresql-doc/html/user/syntax.htm

i'd look in USER documentation under CREATE RULE to get started.
(also at postgresql.org user-lounge area)

--

okay, here's a quickie example:

CREATE VIEW who AS
SELECT * from _who;

CREATE RULE
who_insert
AS ON
INSERT TO who
DO INSTEAD
INSERT INTO "_who" (
login,
"password",
hint,
name,
email,
editor,
status,
modified,
created,
id
) VALUES (
NEW.login,
NEW."password",
NEW.hint,
NEW.name,
NEW.email,
NEW.editor,
'U'::bpchar, -- uncertain until confirmed
"timestamp"('now'::text), -- last mod
"timestamp"('now'::text), -- created now
nextval('_who_id_seq'::text)
);
-- all non-mentioned fields from _who are silently
-- ignored (and dropped).

--
It is always hazardous to ask "Why?" in science, but it is often
interesting to do so just the same.
-- Isaac Asimov, 'The Genetic Code'

will@serensoft.com
http://newbieDoc.sourceforge.net/ -- we need your brain!
http://www.dontUthink.com/ -- your brain needs us!

On Thu, Mar 22, 2001 at 07:14:49PM -0600, will trillich wrote:

CREATE VIEW who AS
SELECT * from _who;

CREATE RULE
who_insert
AS ON
INSERT TO who
DO INSTEAD
INSERT INTO "_who" (
login,
"password",
hint,
name,
email,
editor,
status,
modified,
created,
id
) VALUES (
NEW.login,
NEW."password",
NEW.hint,
NEW.name,
NEW.email,
NEW.editor,
'U'::bpchar, -- uncertain until confirmed
"timestamp"('now'::text), -- last mod
"timestamp"('now'::text), -- created now
nextval('_who_id_seq'::text)
);
-- all non-mentioned fields from _who are silently
-- ignored (and dropped).

now that i think about it...

is it possible to have a rule DO INSTEAD more-than-one-thing?

create rule split_it as
on insert to someview
do instead
insert into tableone ....
then
intert into tabletwo ....
then
insert into tablethree ...
then
update someothertable ...

--
It is always hazardous to ask "Why?" in science, but it is often
interesting to do so just the same.
-- Isaac Asimov, 'The Genetic Code'

will@serensoft.com
http://newbieDoc.sourceforge.net/ -- we need your brain!
http://www.dontUthink.com/ -- your brain needs us!

will trillich <will@serensoft.com> writes:

is it possible to have a rule DO INSTEAD more-than-one-thing?

Sure. Observe the CREATE RULE reference page:

CREATE RULE name AS ON event
TO object [ WHERE condition ]
DO [ INSTEAD ] action

where action can be:

NOTHING
|
query
|
( query ; query ... )
|
[ query ; query ... ]

regards, tom lane