[Postgres-xc-general] question about pg_stat_statements and pg_locks

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

Hi, I'm checking behavior of Postgres-XC 1.0.0.

and I have two questions.

1) pg_stat_statements
when I run INSERT statement to a table with generate_series function,
I can't catch the process from pg_stat_statements on Datanode.
but I can catch it from pg_stat_statements on Coordinator.

so I think generate_series is parsed and divided on Coordinator, and then
each INSERT statement is delivered to each Datanode(this is very short
time).
is this right?

2) pg_locks
when I run SELECT statement to a table on the first of the trunsaction,
I can't catch the lock information(AccessShareLock) from pg_locks on
Datanode.
but I can catch it from pg_locks on Coordinator.

if I run modify statement(INSERT/UPDATE/DELETE) before SELECT statement,
the lock information(AccessShareLock) is appered with the SELECT statement.

I think this behavior is related with virtual-transaction.
and I think AccessShareLock never blocking any other queries,
so this does not become any problems.
is this right?


System Configuration:
---------------------
Architecture : x86_64

Operating Systems : CentOS release 6.2 x86_64

Postgres-XC version : Postgres-XC 1.0.0

Compilers used : gcc (GCC) 4.4.6 20110731 (Red Hat 4.4.6-3)

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Tomonari Katsumata