Обсуждение: Executing multiple statements in a single query?

hi all,
    I am using postgresql from a c application with asyncronous Query
processing. Since only 1 query can be executed at a time, i am using  a
buffering mechanism to store the other queries generated at that time. Is
there any way i can execute all the statements in the buffer with a single
query.

Thanx in advance.

--
regards,
hari

HK <harikrishnan@midascomm.com> writes:
>     I am using postgresql from a c application with asyncronous Query
> processing. Since only 1 query can be executed at a time, i am using  a
> buffering mechanism to store the other queries generated at that time. Is
> there any way i can execute all the statements in the buffer with a single
> query.

You can ship 'em all in a single PQsendQuery string, and wait for the
successive results to come back.  Not sure if that's what you had in
mind...

            regards, tom lane

hi tom,
    Thanx for the reply. Thats wat i am doing. The problem was i didnt
wait for all the replies.
    I have two doubts.
1)  When a table is created in the database, in
    wat file does pg store the data. Also where are the index files
    stored.
2)  In asynchronous queries, can i dispense with pqflush(). If i can, what
    are all the cases where i can do so. On average my queries will be 8k
    in size.

thanx in advance.

--
regards
hari

On Wed, 25 Sep 2002, Tom Lane wrote:

> HK <harikrishnan@midascomm.com> writes:
> >     I am using postgresql from a c application with asyncronous Query
> > processing. Since only 1 query can be executed at a time, i am using  a
> > buffering mechanism to store the other queries generated at that time. Is
> > there any way i can execute all the statements in the buffer with a single
> > query.
>
> You can ship 'em all in a single PQsendQuery string, and wait for the
> successive results to come back.  Not sure if that's what you had in
> mind...
>
>             regards, tom lane
>

HK <harikrishnan@midascomm.com> writes:
> 2)  In asynchronous queries, can i dispense with pqflush().

You don't need PQflush() unless you are using the nonblocking mode
(which I don't really recommend, as it has too many restrictions and
bugs^H^H^H^Hweird behaviors).

            regards, tom lane

hi tom,
    In asyncronous queries, after i send the first query, when should
i send the next query. Will adding the fd of postgrey to writefd in select
of c help.
Or how long do i need to wait before sending the next query.
Thanx in advance.

 On Mon, 30 Sep 2002, Tom Lane wrote:

> HK <harikrishnan@midascomm.com> writes:
> > 2)  In asynchronous queries, can i dispense with pqflush().
>
> You don't need PQflush() unless you are using the nonblocking mode
> (which I don't really recommend, as it has too many restrictions and
> bugs^H^H^H^Hweird behaviors).
>
>             regards, tom lane
>

--
regards,
hari

HK <harikrishnan@midascomm.com> writes:
>     In asyncronous queries, after i send the first query, when should
> i send the next query.

After PQgetResult() returns NULL.

contrib/pgbench is an example of how to use this stuff.  I'm afraid
there are no other examples in the standard PG distribution :-(

            regards, tom lane