Re: [Postgres-xc-general] Question about executing queries against Datanode.

[Tomonari K. <kat...@po...>]

Hi, Michael

Thank you for answer.

 >> I've understood that it's safe to execute against datanode on higher
 >> version of Postgres-XC 1.0.1.
 >> Is this right?
 >>
 > Yes. The read queries are made MVCC-safe when launched directly to
 > Datanodes, so you can have a direct access to the statistics of datanodes
 > by directly connecting to them or monitor them with things like 
Nagios. But
 > you have to be aware that write queries are not blocked in 1.0.X releases
 > when launched directly to Datanodes and this is extremely dangerous 
as you
 > might break data consistency in cluster. Use only read queries!
 >
Alright.
I'll be careful of breaking data consistency.

 > The code on master is made safer and blocks write queries when an
 > application connects to a Datanode that tries to launch a query that may
 > change Database, like a Postgres HOT standby would do.
 >
It's good news.
I'll check the master code.

Thank you again.

regards,
--------
Tomonari Katsumata