PGSQL Trigger Function Write Exception to Log Table

问题

Background

I'm new to PostgreSQL and I'm having some issues with this trigger function, which I've obviously simplified considerably below. I could ask to help fix the query, but I think I can handle that, and what I'm more concerned about is that I have a lot of functions like this and I need a way to be able to have visibility into why it's failing, and which ones are failing.

Question

How can I catch exceptions that happen within this function and write them to some kind of log table so I can review and fix each one? Ideally I'd like to write the sql statement that failed to the log table as well so I can see specifically what went wrong. I've seen a few examples of similar things, but they don't seem to fit my scenario.

CREATE OR REPLACE FUNCTION my_func() RETURNS TRIGGER AS $$
   BEGIN
        IF (TG_OP = 'INSERT') THEN

            INSERT INTO my_table(...)
            SELECT ...
            FROM table_1 t1
            JOIN table_2 t2 ON t1.id = t2.id               
            ON CONFLICT (id)
            DO UPDATE
            field1 = EXCLUDED.field1;

        ELSIF(TG_OP = 'UPDATE') THEN

            UPDATE my_table 
            SET ...
            FROM table_1 t1
            JOIN table_2 t2 ON t1.id = t2.id
            WHERE id = NEW.id;

         ELSIF (TG_OP = 'DELETE') THEN
            DELETE FROM my_table WHERE id= OLD.id;
        END IF;
      RETURN NULL;
   END;
$$ LANGUAGE plpgsql;

回答1:

Here's an example, using a normal function rather than a trigger, though it's really the same thing in as far as how to log:

Table to store errors:

CREATE TABLE errors (id SERIAL, sql_state TEXT, message TEXT, detail TEXT, hint TEXT, context TEXT);

Function which does work and has the exception handling/logging:

CREATE OR REPLACE FUNCTION my_func()
    RETURNS VOID AS
$BODY$
DECLARE
    _sql_state TEXT;
    _message TEXT;
    _detail TEXT;
    _hint TEXT;
    _context TEXT;
BEGIN
    PERFORM 1 / 0;
EXCEPTION
    WHEN OTHERS THEN
        GET STACKED DIAGNOSTICS
            _sql_state := RETURNED_SQLSTATE,
            _message := MESSAGE_TEXT,
            _detail := PG_EXCEPTION_DETAIL,
            _hint := PG_EXCEPTION_HINT,
            _context := PG_EXCEPTION_CONTEXT;

        INSERT INTO errors (sql_state, message, detail, hint, context)
        VALUES (_sql_state, _message, _detail, _hint, _context);
END
$BODY$
    LANGUAGE plpgsql;

After calling the function, the errors table contains:

See https://rextester.com/BQPG27732

Context shows a call stack of sorts. You could add more error-related fields of course, I only chose a handful of those available in GET STACKED DIAGNOSTICS

来源：https://stackoverflow.com/questions/53504234/pgsql-trigger-function-write-exception-to-log-table

标签

postgresql

plpgsql