Re: tuple-routing and constraint violation error message, revisited

On Fri, Mar 31, 2017 at 7:43 AM, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> Hi,
>
> Last message regarding this was by Robert on the original partitioning thread:
>
> https://www.postgresql.org/message-id/CA%2BTgmoZjGzSM5WwnyapFaw3GxnDLWh7pm8Xiz8_QWQnUQy%3DSCA%40mail.gmail.com
>
> Summary is: We decided in f1b4c771ea7 [1] that passing the original slot
> (one containing the tuple formatted per root partitioned table's tupdesc)
> to ExecConstraints(), but that breaks certain cases. Imagine what would
> happen if a BR insert trigger changed the tuple - the original slot would
> not contain those changes. So, it seems better to convert (if necessary)
> the tuple formatted per partition tupdesc after tuple-routing back to the
> root table's format and use the converted tuple to make val_desc shown in
> the message if an error occurs.
>
> Attached rebased version of the patch that I had originally proposed
> (summary above is the commit message). Robert thought it would be fine to
> show the row formatted per partition rowtype, but would look better if we
> could show the column names as well (remember that we're trying to account
> for possible differences in the ordering of columns between the root table
> and leaf partitions to which tuples are routed.)
>
> Added this to PostgreSQL 10 open items list.

The changes look good to me. Now, ExecConstraint() has three blocks
which are almost similar, differing only in the constraints checked
and the error message. It was manageable without partitioning and may
be it's still manageable, but it's certainly being pushed to the
limits. May be we should refactor error reporting code into a separate
function and call it in those three places.

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company