id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
17266	psycopg2 backend should use get_parameter_status to check if SET TIME ZONE is needed	Anssi Kääriäinen	Aymeric Augustin	"In ticket #17062 Aymeric Augustin suggested the idea for using get_parameter_status to check if the database default time zone is already correct. If it is, we can skip the SET TIME ZONE and associated isolation level handling for every new connection. Ticket #17062 has more details, but I will copy-paste the most relevant parts here. If this is not done, for every new connection we need to do these queries:
{{{
26639: LOG:  connection authorized: user=akaj database=testdb1
26639: LOG:  statement: SHOW default_transaction_isolation
26639: LOG:  statement: SET default_transaction_isolation TO DEFAULT
26639: LOG:  statement: SET TIME ZONE 'America/Chicago'
26639: LOG:  statement: SET default_transaction_isolation TO 'read uncommitted'
26639: LOG:  statement: BEGIN
26639: LOG:  statement: first real query...
}}}

If we use get_parameter_status, we can get it down to this:
{{{
27163: LOG:  connection authorized: user=akaj database=testdb1
27163: LOG:  statement: SHOW default_transaction_isolation
27163: LOG:  statement: BEGIN
27163: LOG:  statement: first real query
}}}

The get_parameter_status was added in psycopg2 version 2.0.12 [http://initd.org/psycopg/docs/connection.html#connection.get_parameter_status]. I can't find a mention if we need to support versions prior to this. If we need to support versions prior to 2.0.12, we can just add a check for the psycopg2 version in use and not use get_parameter_status if the version doesn't support it.

I will wait until ticket #17062 gets fixed before working on this."	Cleanup/optimization	closed	Database layer (models, ORM)		Normal	fixed			Ready for checkin	1	0	0	0	0	0