[pgpool-hackers: 427] Proposal: variant of regclass

[Tatsuo Ishii]

I would like to propose to add a variant of regclass.

Background:

Pgpool-II (http://www.pgpool.net) needs to get information of tables
by querying PostgreSQL's system catalog. For efficiency and
correctness of the info (search path consideration), pgpool-II issues
such queries piggy packing the user's connection to PostgreSQL and
regclass is frequently used in the queries.

One problem with stock regclass is, it raises exception when a target
tables is not found, which breaks user's transaction currently running
on the session. For a workaround, pgpool-II ships non-error-raising
version of regclass, called pgpool_regclass. However it's not perfect
solution because people (or even distributions/packagers) forget to
install it [1]. Another problem is, pgpool_regclass heavily depends on
the internals of PostgreSQL, which has been changed version to
versions and pgpool developers need to spend some efforts to adopt the
changes.

Someone suggested before that pgpool_regclass could be implemented as
a pl function, but I think it is unacceptable because 1) the function
is heavily used and using pl will cause performance problem, 2) it
does solve the problem I said in [1].

Proposal:
I would like to add a variant of regclass, which is exactly same as
current regclass except it does not raise an error when the target
table is not found. Instead it returns InvalidOid (0).

Pgpool-II is being shipped with various distributions and used by many
companies including EnterpriseDB, VMWare, SRA OSS and so on. IMO this
small enhancement will benefit many PostgreSQL users by small changes
to PostgreSQL.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp