Re: Triggers on columns

Here is a updated version of column-trigger patch.

Changes from the previous patch:
* Add dependency of columns with recordDependencyOn().
Regression tests are also adjusted.
* Recheck columns if NEW values are modified, but each trigger
will be firec only one per row.

Peter Eisentraut <peter_e(at)gmx(dot)net> wrote:
> The SQL standard specifies that a trigger is fired if the column is
> mentioned in the UPDATE statement, independent of whether the value is
> actually changed through the update.

We are discussing how to determine modified columns
(UPDATE-target vs. changes of actual values), but in the patch
I used value-based checking. The reasons are:
1. Other triggers could modify referred columns even if the columns
are not specifed in UPDATE-target.
2. IMHO, almost users don't expect their triggers are not called
if the actual values are not modified.
3. Restriction of implementation; We don't have RTE in trigger
routine for now. The current patch doesn't modify codes a lot.

Comments welcome.

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