pgpool_regclass

Overview

Version

Install

You can install pgpool directly. First, make sure the PGDG repository is added and enabled:

pig repo add pgdg -u          # Add PGDG repo and update cache

Install the extension using pig or apt/yum/dnf:

pig install pgpool;          # Install for current active PG version

pig ext install -y pgpool -v 18  # PG 18
pig ext install -y pgpool -v 17  # PG 17
pig ext install -y pgpool -v 16  # PG 16
pig ext install -y pgpool -v 15  # PG 15
pig ext install -y pgpool -v 14  # PG 14

dnf install -y pgpool-II-pg18-extensions       # PG 18
dnf install -y pgpool-II-pg17-extensions       # PG 17
dnf install -y pgpool-II-pg16-extensions       # PG 16
dnf install -y pgpool-II-pg15-extensions       # PG 15
dnf install -y pgpool-II-pg14-extensions       # PG 14

apt install -y postgresql-18-pgpool2   # PG 18
apt install -y postgresql-17-pgpool2   # PG 17
apt install -y postgresql-16-pgpool2   # PG 16
apt install -y postgresql-15-pgpool2   # PG 15
apt install -y postgresql-14-pgpool2   # PG 14

Create Extension:

CREATE EXTENSION pgpool_regclass;

Usage

pgpool_regclass: replacement for regclass

The pgpool_regclass extension provides a replacement regclass function used internally by Pgpool-II to handle relation name resolution across multiple backends.

Function

-- Resolve a relation name to its OID, similar to PostgreSQL's regclass cast
SELECT pgpool_regclass('my_table');
SELECT pgpool_regclass('my_schema.my_table');

Purpose

In standard PostgreSQL, casting a string to regclass (e.g., 'my_table'::regclass) resolves the relation name to an OID. However, Pgpool-II needs to determine whether a SQL statement references a temporary table or a regular table to route queries correctly.

The pgpool_regclass function provides this resolution capability as a regular function call rather than a type cast, allowing Pgpool-II to:

• Determine if a referenced table exists on the backend
• Distinguish temporary tables from permanent tables for proper query routing
• Handle schema-qualified table names correctly across pooled connections

Notes

• This extension is primarily used internally by Pgpool-II and is not typically called directly by applications
• It should be installed on all PostgreSQL backend nodes managed by Pgpool-II
• For Pgpool-II 3.0+, this function helps with the check_temp_table feature