How to implement connection pooling in PostgreSQL?

Connection pooling is a technique used to improve the performance of database applications by reusing database connections rather than creating new ones for each request. In PostgreSQL, connection pooling can be implemented using a third-party tool like PgBouncer or by using the built-in connection pooler, pgpool-II.

Here are the steps to implement connection pooling using pgpool-II:

1. Step 1- Install pgpool-II: Install pgpool-II on the same server where the PostgreSQL database is running or on a separate server.
2. Step 2 – Configure pgpool-II: Edit the pgpool.conf file to set the pool mode, maximum number of connections, and other configuration options.
3. Step 3 – Configure PostgreSQL: Edit the postgresql.conf file to allow connections from pgpool-II.
4. Step 4 – Start pgpool-II: Start pgpool-II using the pgpool executable.
5. Step 5 – Test connection pooling: Connect to the PostgreSQL database using pgpool-II and test the connection pooling.

Here is a sample pgpool.conf file:

#------------------------------------------------------------------------------
# CONNECTION POOLING
#------------------------------------------------------------------------------

# - Pool mode -

# Connection pool mode
#   0: off
#   1: session pool mode
#   2: transaction pool mode
pool_mode = 2

# - Connection settings -

# Maximum number of connections
max_pool = 100

# Connection timeout
#   0: no timeout
connection_life_time = 0

# - Authentication -

# Authentication method
#   trust
#   plain
#   md5
#   password
auth_method = md5

# PostgreSQL connection string
backend_hostname0 = localhost
backend_port0 = 5432
backend_weight0 = 1
backend_database_name0 = mydatabase
backend_username0 = myuser
backend_password0 = mypassword

After configuring the pgpool-II, start the pgpool-II service and connect to the PostgreSQL database using the pgpool-II connection pool.