Обсуждение: Session variables (how do I pass session data to a function)
I have a question on how to do something with Postgres that I think
of by the name of "Session Variables".
What I want to do is build a table that will be filled in by a trigger,
it will contains three fields in addition to the fields in the table
that causes the trigger that will contain the time, user and the "proxy
user" for the change (this is an audit table) I have the following example
that handles the first two extra fields correctly:
--------------------------------------------------------
CREATE TABLE partypersons (
partyid TEXT,
firstname TEXT,
middlename TEXT,
lastname TEXT,
personaltitle TEXT,
suffex TEXT,
employmentstatus TEXT,
residencestatus TEXT,
maritalstatus TEXT,
PRIMARY KEY (partyid)
)
;
CREATE TABLE partypersons_audit (
audit_when TIMESTAMP,
audit_who TEXT,
partyid TEXT,
firstname TEXT,
middlename TEXT,
lastname TEXT,
personaltitle TEXT,
suffex TEXT,
employmentstatus TEXT,
residencestatus TEXT,
maritalstatus TEXT,
PRIMARY KEY (partyid,audit_when)
)
;
ALTER TABLE partypersons ADD
FOREIGN KEY ( partyid ) REFERENCES partys ( partyid )
;
-- AUDIT FOR PARTYPERSON
CREATE OR REPLACE FUNCTION fauditpartypersons() RETURNS TRIGGER AS $fauditpartypersons$
DECLARE
BEGIN
IF (TG_OP = 'UPDATE') THEN
IF (OLD.firstname = NEW.firstname) THEN
NEW.firstname := NULL;
END IF;
IF (OLD.middlename = NEW.middlename) THEN
NEW.middlename := NULL;
END IF;
IF (OLD.lastname = NEW.lastname) THEN
NEW.lastname := NULL;
END IF;
IF (OLD.personaltitle = NEW.personaltitle) THEN
NEW.personaltitle := NULL;
END IF;
IF (OLD.suffex = NEW.suffex) THEN
NEW.suffex := NULL;
END IF;
IF (OLD.employmentstatus = NEW.employmentstatus) THEN
NEW.employmentstatus := NULL;
END IF;
IF (OLD.residencestatus = NEW.residencestatus) THEN
NEW.residencestatus := NULL;
END IF;
IF (OLD.maritalstatus = NEW.maritalstatus) THEN
NEW.maritalstatus := NULL;
END IF;
END IF;
INSERT INTO partypersons_audit SELECT now(), user, NEW.*;
RETURN NULL;
END;
$fauditpartypersons$ LANGUAGE plpgsql;
CREATE TRIGGER auditpartyperson AFTER UPDATE OR INSERT
ON partypersons FOR ROW
EXECUTE PROCEDURE fauditpartypersons ()
;
--------------------------------------------------------
As you can see the primary key and the time and user are always set
while the other fields are NULL unless an update (or insert) changes
them.
What I want to do is to add to this another field that will be NULL
UNLESS the session sets a value to the "user" for that the middle-wear
system is acting for.
What this will be used for will be a web system that will access the
DB as the user apache but I want to do two things:
1) log to the audit table all changes even if they are done outside of
the web interface (this is done by the above system)
2) in the same log allow the system (apache) to also say who it is "acting
for"
Thanks.
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Philip W. Dalrymple III <pwd@mdtsoft.com>
MDT Software - The Change Management Company
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Fax +1 678 297 1003
Philip,
"session variables" is the perfect name for this kind of use; and
googling it up some times ago lead me to
a) a temp table implementation
b) some shared memory implementation
of these I can present you with a), written to store an integer
user-ID; you can adjust it accordingly:
CREATE OR REPLACE FUNCTION set_user(myid_user integer)
RETURNS integer AS
$BODY$
BEGIN
perform relname from pg_class
where relname = 'icke_tmp'
and case when has_schema_privilege(relnamespace, 'USAGE')
then pg_table_is_visible(oid) else false end;
if not found then
create temporary table icke_tmp (
id_user integer
);
else
delete from icke_tmp;
end if;
insert into icke_tmp values (myid_user);
RETURN 0;
END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE
COST 100;
CREATE OR REPLACE FUNCTION get_user()
RETURNS integer AS
$BODY$
declare
ergebnis int4;
BEGIN
perform relname from pg_class
where relname = 'icke_tmp'
and case when has_schema_privilege(relnamespace, 'USAGE')
then pg_table_is_visible(oid) else false end;
if not found then
return 0;
else
select id_user from icke_tmp into ergebnis;
end if;
if not found then
ergebnis:=0;
end if;
RETURN ergebnis;
END;
$BODY$
LANGUAGE 'plpgsql' STABLE
COST 100;
You can adjust that "0" to NULL or whatever should be the default for
your application. In mine I default to 0; with 0 being something like
"testuser".
best wishes,
Harald
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Philip W. Dalrymple wrote: > > What I want to do is to add to this another field that will be NULL > UNLESS the session sets a value to the "user" for that the middle-wear > system is acting for. This can be done via a setting. See http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADMIN-SET-TABLE If you'd like to read a fuller discussion of this very topic, search for a thread titled "can I define own variables" in the archives. I had to do the same thing back then. -- Guy Rouillier
Just to complete the answer in this thread; the trick is to do the following: - define in your postgresql.conf: custom_variable_classes = 'myvar' Then see http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADMIN-SET-TABLE ( with the variables named myvar.*) thanks for everyone's help on this. ----- Original Message ----- From: "Guy Rouillier" <guyr-ml1@burntmail.com> To: "General Postgres Mailing List" <pgsql-general@postgresql.org> Sent: Monday, October 20, 2008 7:22:22 PM GMT -05:00 US/Canada Eastern Subject: Re: [GENERAL] Session variables (how do I pass session data to a function) Philip W. Dalrymple wrote: > > What I want to do is to add to this another field that will be NULL > UNLESS the session sets a value to the "user" for that the middle-wear > system is acting for. This can be done via a setting. See http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADMIN-SET-TABLE If you'd like to read a fuller discussion of this very topic, search for a thread titled "can I define own variables" in the archives. I had to do the same thing back then. -- Guy Rouillier -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general -- This email, and any files transmitted with it, is confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error, please advise postmaster@mdtsoft.com <mailto:postmaster@mdtsoft.com>. New MDT Software Headquarters (As of July 1, 2008): 3480 Preston Ridge Road Suite 450 Alpharetta, GA 30005 Philip W. Dalrymple III <pwd@mdtsoft.com> MDT Software - The Change Management Company +1 678 297 1001 Fax +1 678 297 1003