Based on a diff provided by Mustafa Dogan.
4.2.1 and 4.2.2 are bugfix releases.
4.2 contains new features and enhancements, including:
Some items in the configuration file pgpool.conf are vastly
enhanced for easier configuration and administration.
Implement logging_collector for easier log management.
Implement log_disconnections to collect disconnection logs.
Implement pg_enc and pg_md5 to allow to register multiple
passwords at once.
Allow to show statistics of health check by using SHOW
POOL_HEALTH_CHECK_STATS command, and also allow to show statistics
of issued SQL by using SHOW POOL_BACKEND_STATS command.
New PCP command pcp_reload_config is added.
Now it is possible to omit write_function_list and
read_only_function_list by looking at system catalog information.
Add new clustering mode snapshot_isolation_mode which guarantees
not only data modifications to multiple PostgreSQL but read
consistency.
Support LDAP authentication between clients and Pgpool-II.
Add ssl_crl_file and ssl_passphrase_command to SSL configuration.
Import PostgreSQL 13's SQL parser.
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