Re: TRIGGER with WHEN clause

Thank for your reviewing!

KaiGai Kohei <kaigai@kaigai.gr.jp> wrote:

> However, I could find a few matters in this patch, as follows:
>
> * It does not prevent set up a conditional "statement" trigger.

I fixed the bug and two other bugs:
  * Crash in AFTER TRIGGER + WHEN clause.
  * Incorrect behavior when multiple tuples are modified.
Also regression tests for it are added.

> I'm uncertain how Oracle handles the condition on the statement
> triggers. But it seems to me WHEN clause on the statement triggers
> are nonsense.

I am also not sure about Oracle, but I think there are usage of
statement trigger with WHEN cluase something like:
  =# CREATE TRIGGER log_trig BEFORE UPDATE ON tbl
       WHEN (is_superuser()) EXECUTE PROCEDURE log_current_stmt();

> * the documentation seems to me misleading.
> It saids, NEW and OLD are only available and ...
>  o INSERT can refer NEW
>  o UPDATE can refer NEW, OLD
>  o DELETE can refer OLD
> But, it may actually incorrect, if user gives several events on a certain
> trigger. For example, when a new trigger is invoked for each row on INSERT
> or UPDATE statement, the function cannot refer the OLD.

They are bitwise-AND flags. INSERT-OR-DELETE trigger cannot refer to both
OLD and NEW tuples. It is possible to use a dummy tuple (filled with NULLs?)
in the cases, but I want to just throw an error as of now. I'll fix
documentation to reflect the code. Ideas for better descriptions welcome.

| Note that if a trigger has multiple events, it can refer only tuples
| that can be referred in all of the events. For example,
| INSERT OR DELETE trigger cannot refer neither NEW nor OLD tuples.

> * A minor coding style
> Is it unnecessary to set InvalidOid on the values[Anum_pg_trigger_tgqual - 1]?

Strange. There was something wrong with me.

> * doc/src/sgml/catalogs.sgml is not updated
> Could you add a short description about pg_trigger.tgqual system catalog?

Added.

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center