logtriga - generic table changes logger
=======================================

logtriga provides generic table changes logging trigger.
It prepares partial SQL statement about a change and
gives it to user query.

Usage
-----

   CREATE TRIGGER foo_log AFTER INSERT OR UPDATE OR DELETE ON foo_tbl
   FOR EACH ROW EXECUTE PROCEDURE logtriga(column_types, query);

Where column_types is a string where each charater defines type of
that column.  Known types:

 * k - one of primary key columns for table.
 * v - data column
 * i - uninteresting column, to be ignored.

Trigger function prepares 2 string arguments for query and executes it.

 * $1 - Operation type: I/U/D.
 * $2 - Partial SQL for event playback.

   * INSERT INTO FOO_TBL (field, list) values (val1, val2)
   * UPDATE FOO_TBL SET field1 = val1, field2 = val2 where key1 = kval1
   * DELETE FROM FOO_TBL WHERE key1 = keyval1

The upper-case part is left out.

Example
-------

Following query emulates Slony-I behaviour:

   insert into SL_SCHEMA.sl_log_1
          (log_origin, log_xid, log_tableid,
           log_actionseq, log_cmdtype, log_cmddata)
   values (CLUSTER_IDENT, SL_SCHEMA.getCurrentXid(), TABLE_OID,
           nextval('SL_SCHEMA.sl_action_seq'), $1, $2)

The upper-case strings should be replaced with actual values
on trigger creation.