Jasen Betts schrieb:
On 2010-05-11, Torsten Zühlsdorff f...@meisterderspiele.de wrote:
Hello,
i have a problem with a trigger written in pl/pgsql.
It looks like this:
CREATE OR REPLACE FUNCTION versionize()
RETURNS TRIGGER
AS $$
BEGIN
NEW.revision := addContentRevision (OLD.content_id, OLD.revision);
/* not working line, just a stub:
EXECUTE 'INSERT INTO ' || TG_TABLE_NAME || ' SELECT $1 ' USING NEW;
*/
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql' VOLATILE;
The function should be used at different tables and is invoked before
UPDATEs. Everything what happens is the function call of
addContentRevision. After this call all data (with the updated revision
column) should be stored in the table as a new row.
What many people have missed is that you want to INSERT when the DML
comnabd UPDATE is used.
for things like that usually a rule is used instead, but I can see where
that may be unsuitable for your needs. I found the following
to work on a simple test case.
The problem is that INSERT in PLPGSQL needs a fixed table-name, and
that EXECUTE can't use variable-names, and further that quote_literal
doesn't convert ROW variables into something that can be used in a
VALUES clause.
so, Here's what I did.
CREATE OR REPLACE FUNCTION versionize()
RETURNS TRIGGER
AS $$
BEGIN
-- Not havign a definition for addContentRevision
-- I had this line commented out during testing.
NEW.revision := addContentRevision (OLD.content_id, OLD.revision);
EXECUTE 'INSERT INTO '||TG_TABLE_NAME||' SELECT (' ||
QUOTE_LITERAL(NEW) || '::' || TG_TABLE_NAME ||').*' ;
RETURN NULL;
END;
$$ LANGUAGE PLPGSQL VOLATILE;
I take NEW, convert it to a quoted literal so I can use it in EXECUTE, cast it
to the apreopreiate row type and split it into columns using SELECT
and .*. That gets inserted.
you should probably use QUOTE_IDENT on the TG_TABLE_NAME and possibly
also use similarly quoted TG_SCHEMA_NAME
That's an quite interesting solution. I've tested it in several ways and
it works like i want. :)
Thank you very much - and every other responder - for your time.
Greetings from Germany,
Torsten
--
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verschiedenen Datenbanksystemen abstrahiert,
Queries von Applikationen trennt und automatisch die Query-Ergebnisse
auswerten kann.
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