[pgpool-hackers: 2726] Proposal: Disabling load balance after writing query

[Tatsuo Ishii]

Currently we have a feature to disable load balancing in a transaction
if write query is sent. This allows legacy applications that do not
consider streaming replication delay to be used with PostgreSQL's
streaming replication. However, if the transaction closes, in the
subsequent transaction load balancing starts again, which maybe not
good for read query because of the replication delay.

So my proposal is, adding a new configuration parameter called
"disable_load_balance_on_write" to allow more control on the existing
feature. Here are possible values for the configuration:

off: completely disable prohibiting load balance feature, including
existing behavior.

transaction: same as current behavior, i.e. if write query is sent,
load balance is disabled within the transaction.

trans_transaction: the effect of "transaction" will continue in
the subsequent transactions.

always: the effect will continue even out side of transactions.

Comments and suggestions are welcome.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp