[GENERAL] passing parameters to a trigger function
I can't figure out how to pass parameters to a trigger function. I checked the documentation and saw that trigger functions don't take params in the usual fashion, but couldn't find an example of a pl-sql trigger function that used the original row data within the function. What I want is an on update trigger that creates an entry in a second table. The second (history) table has a subset of the columns in the first.Here's what I have so far: -- THIS IS WRONG - CANT PASS PARAMS INTO TRIGGER FUNCTION CREATE OR REPLACE FUNCTION audit_task (param type declarations were here) RETURNS TRIGGER AS ' -- create an audit trail recordBEGIN -- Perform the insert INSERT INTO TASK_h (id, updated_by, updated, name, description ) VALUES ($1, $2, $3, $4, $5); RETURN NULL; END;' LANGUAGE plpgsql;-- THE TRIGGERCREATE TRIGGER t_audit_task AFTER INSERT OR UPDATE ON task FOR EACH ROW EXECUTE PROCEDURE audit_task(); So the question is, how do I access the row from the original table so I can perform the insert? Thank you much.
Re: [GENERAL] passing parameters to a trigger function
On Tuesday 21 March 2006 09:21 am, Larry White saith: I can't figure out how to pass parameters to a trigger function. I checked the documentation and saw that trigger functions don't take params in the usual fashion, but couldn't find an example of a pl-sql trigger function that used the original row data within the function. What I want is an on update trigger that creates an entry in a second table. The second (history) table has a subset of the columns in the first. Here's what I have so far: -- THIS IS WRONG - CANT PASS PARAMS INTO TRIGGER FUNCTION CREATE OR REPLACE FUNCTION audit_task (param type declarations were here) RETURNS TRIGGER AS ' -- create an audit trail record BEGIN -- Perform the insert INSERT INTO TASK_h (id, updated_by, updated, name, description ) VALUES ($1, $2, $3, $4, $5); RETURN NULL; END; ' LANGUAGE plpgsql; -- THE TRIGGER CREATE TRIGGER t_audit_task AFTER INSERT OR UPDATE ON task FOR EACH ROW EXECUTE PROCEDURE audit_task(); So the question is, how do I access the row from the original table so I can perform the insert? Thank you much. If I understand your question correctly, this documentation addresses your problem: 37.10. Trigger Procedures PL/pgSQL can be used to define trigger procedures. A trigger procedure is created with the CREATE FUNCTION command, declaring it as a function with no arguments and a return type of trigger. Note that the function must be declared with no arguments even if it expects to receive arguments specified in CREATE TRIGGER --- trigger arguments are passed via TG_ARGV, as described below. When a PL/pgSQL function is called as a trigger, several special variables are created automatically in the top-level block. They are: NEW Data type RECORD; variable holding the new database row for INSERT/UPDATE operations in row-level triggers. This variable is null in statement-level triggers. OLD Data type RECORD; variable holding the old database row for UPDATE/DELETE operations in row-level triggers. This variable is null in statement-level triggers. TG_NAME Data type name; variable that contains the name of the trigger actually fired. TG_WHEN Data type text; a string of either BEFORE or AFTER depending on the trigger's definition. TG_LEVEL Data type text; a string of either ROW or STATEMENT depending on the trigger's definition. TG_OP Data type text; a string of INSERT, UPDATE, or DELETE telling for which operation the trigger was fired. TG_RELID Data type oid; the object ID of the table that caused the trigger invocation. TG_RELNAME Data type name; the name of the table that caused the trigger invocation. TG_NARGS Data type integer; the number of arguments given to the trigger procedure in the CREATE TRIGGER statement. TG_ARGV[] Data type array of text; the arguments from the CREATE TRIGGER statement. The index counts from 0. Invalid indices (less than 0 or greater than or equal to tg_nargs) result in a null value. A trigger function must return either null or a record/row value having exactly the structure of the table the trigger was fired for. Row-level triggers fired BEFORE may return null to signal the trigger manager to skip the rest of the operation for this row (i.e., subsequent triggers are not fired, and the INSERT/UPDATE/DELETE does not occur for this row). If a nonnull value is returned then the operation proceeds with that row value. Returning a row value different from the original value of NEW alters the row that will be inserted or updated (but has no direct effect in the DELETE case). To alter the row to be stored, it is possible to replace single values directly in NEW and return the modified NEW, or to build a complete new record/row to return. The return value of a BEFORE or AFTER statement-level trigger or an AFTER row-level trigger is always ignored; it may as well be null. However, any of these types of triggers can still abort the entire operation by raising an error. Example 37-1 shows an example of a trigger procedure in PL/pgSQL. Example 37-1. A PL/pgSQL Trigger Procedure This example trigger ensures that any time a row is inserted or updated in the table, the current user name and time are stamped into the row. And it checks that an employee's name is given and that the salary is a positive value. CREATE TABLE emp ( empname text, salary integer, last_date timestamp, last_user text ); CREATE FUNCTION emp_stamp() RETURNS trigger AS ' BEGIN -- Check that empname and salary are given IF NEW.empname IS NULL THEN RAISE EXCEPTION ''empname cannot be null''; END IF; IF NEW.salary IS NULL THEN RAISE EXCEPTION ''% cannot have null salary'', NEW.empname; END
Re: [GENERAL] passing parameters to a trigger function
On Tue, Mar 21, 2006 at 09:21:43AM -0500, Larry White wrote: I can't figure out how to pass parameters to a trigger function. I checked the documentation and saw that trigger functions don't take params in the usual fashion, but couldn't find an example of a pl-sql trigger function that used the original row data within the function. Check the docs. It varies by language, but this is for plpgsql: http://www.postgresql.org/docs/8.0/static/plpgsql-trigger.html Have a nice day, -- Martijn van Oosterhout kleptog@svana.org http://svana.org/kleptog/ Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a tool for doing 5% of the work and then sitting around waiting for someone else to do the other 95% so you can sue them. signature.asc Description: Digital signature
Re: [GENERAL] passing parameters to a trigger function
On Tue, 21 Mar 2006, Larry White wrote: I can't figure out how to pass parameters to a trigger function. I checked the documentation and saw that trigger functions don't take params in the usual fashion, but couldn't find an example of a pl-sql trigger function that used the original row data within the function. What I want is an on update trigger that creates an entry in a second table. The second (history) table has a subset of the columns in the first. Here's what I have so far: -- THIS IS WRONG - CANT PASS PARAMS INTO TRIGGER FUNCTION CREATE OR REPLACE FUNCTION audit_task (param type declarations were here) RETURNS TRIGGER AS ' -- create an audit trail record BEGIN -- Perform the insert INSERT INTO TASK_h (id, updated_by, updated, name, description ) VALUES ($1, $2, $3, $4, $5); RETURN NULL; END; ' LANGUAGE plpgsql; -- THE TRIGGER CREATE TRIGGER t_audit_task AFTER INSERT OR UPDATE ON task FOR EACH ROW EXECUTE PROCEDURE audit_task(); So the question is, how do I access the row from the original table so I can perform the insert? The old row is OLD and the new row NEW and do not need to be declared as arguments (in fact trigger functions are always currently created without declared arguments). I think section 36.10 in the 8.1 docs has info for other implicit arguments to plpgsql trigger functions. ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [GENERAL] passing parameters to a trigger function (solved)
Thank you. You guys rock!On 3/21/06, Stephan Szabo [EMAIL PROTECTED] wrote: On Tue, 21 Mar 2006, Larry White wrote: I can't figure out how to pass parameters to a trigger function. I checked the documentation and saw that trigger functions don't take params in the usual fashion, but couldn't find an example of a pl-sql trigger function that used the original row data within the function. What I want is an on update trigger that creates an entry in a second table.The second (history)table has a subset of the columns in the first. Here's what I have so far: -- THIS IS WRONG - CANT PASS PARAMS INTO TRIGGER FUNCTION CREATE OR REPLACE FUNCTION audit_task (param type declarations were here) RETURNS TRIGGER AS ' -- create an audit trail record BEGIN -- Perform the insert INSERT INTO TASK_h(id,updated_by,updated,name, description) VALUES ($1, $2, $3, $4, $5); RETURN NULL; END; ' LANGUAGE plpgsql; -- THE TRIGGER CREATE TRIGGER t_audit_task AFTER INSERT OR UPDATE ON task FOR EACH ROW EXECUTE PROCEDURE audit_task(); So the question is, how do I access the row from the original table so I can perform the insert?The old row is OLD and the new row NEW and do not need to be declared asarguments (in fact trigger functions are always currently created withoutdeclared arguments).I think section 36.10 in the 8.1 docs has info forother implicit arguments to plpgsql trigger functions.
