Thread: Altering field passed as parameter to plpgsql trigger
I am trying to make a function that can be reused as a trigger on various tables but am somehow not finding the correct syntax for using a parameter to the function to identify the column to be altered by the trigger. Stripped to basics: create or replace function foo_trigger() returns trigger as ' declare ... begin trigger_table = TG_ARGV[0]; field_to_alter = TG_ARGV[1]; ... new.field_to_alter = some_computed_value; <<========== return new; end;' language 'plpgsql'; create trigger foo_change before insert on foo for each row execute procedure foo_trigger('foo','somealteredfield'); What is the correct syntax for the line: new.field_to_alter = some_computed_value; Also, does plpgsql have a preferred way to identify the table that fired the trigger. I see the syntax for C but not for plpgsql. Cheers, Steve
Steve Crawford wrote: > What is the correct syntax for the line: > new.field_to_alter = some_computed_value; Can't be done in plpgsql - it's too static a language. On first call, that assignments basically gets compiled into a planned query and from then on you're stuck. You can use pl/tcl or pl/perl etc. since they're more dynamic. > Also, does plpgsql have a preferred way to identify the table that fired > the trigger. I see the syntax for C but not for plpgsql. TG_RELNAME / TG_TABLE_NAME - it's in the plpgsql/triggers section of the manual. -- Richard Huxton Archonet Ltd
Richard Huxton wrote: > Steve Crawford wrote: > >> What is the correct syntax for the line: >> new.field_to_alter = some_computed_value; > > Can't be done in plpgsql - it's too static a language. On first call, > that assignments basically gets compiled into a planned query and from > then on you're stuck. > > You can use pl/tcl or pl/perl etc. since they're more dynamic. Great. I'll use another approach. >> Also, does plpgsql have a preferred way to identify the table that >> fired the trigger. I see the syntax for C but not for plpgsql. > > TG_RELNAME / TG_TABLE_NAME - it's in the plpgsql/triggers section of > the manual. > Thanks. I did find that after another cup of coffee. :) Cheers, Steve