Re: SQL/PostgreSQL - Error observed in the QUERY not caught by the “EXCEPTION” block in the stored procedure

=?UTF-8?Q?Eduardo_L=C3=BAcio_Amorim_Costa?= <eduardolucioac(at)gmail(dot)com> writes:
> my_database=# SELECT file INTO my_file_now FROM public.my_datatable WHERE
> my_id='2fdf5297-8d4a-38bc-bb26-b8a4b7ba47ec';
> ERROR: missing chunk number 0 for toast value 3483039 in pg_toast_3473493

We've fixed a few bugs over the years that manifest in that type of
problem --- are you up to date on minor releases? It's also possible
that reindexing that toast table would fix it.

> Based on the above behavior I created the following stored procedure:
> ...
> my_file_now BYTEA;
> ...
> SELECT file
> INTO my_file_now
> FROM public.my_datatable WHERE my_id=my_id_now;

> QUESTION: Why is the error observed in the query not caught by the
> "EXCEPTION" block in the stored procedure?

I think that plpgsql will not bother to dereference a TOAST pointer
when storing it into a local variable (although this statement is
very possibly version-dependent, and you didn't say what PG version
you are using).

A more reliable way to trigger the problem is to do some computation
that requires the value of the field, perhaps along the lines of

PERFORM md5(file) FROM public.my_datatable WHERE my_id=my_id_now;

> EXCEPTION
> WHEN OTHERS THEN
> RAISE NOTICE 'CORRUPTED MY_ID - % ', my_id_now;
> DELETE FROM public.my_datatable WHERE my_id=my_id_now;

I don't know that I'd give a procedure like this license to delete my
entire table :-(. If you really don't care how much data survives,
why not just TRUNCATE the table and be done with it? Otherwise,
printing the list of troublesome rows for manual review seems way
more prudent.

regards, tom lane