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* libpq PQexec call of COPY
@ 2001-04-09 20:58 John Coers <coers@intrinsity.com>
0 siblings, 1 reply; 2+ messages in thread
From: John Coers @ 2001-04-09 20:58 UTC (permalink / raw)
To: pgsql-hackers@postgresql.org
Hi,
My generic problem is performance when copying very large amounts of data to a db from multiple clients.
I am writing a C program on Linux Redhat6.2 that accesses a 7.0.3 database using libpq. I
would like to be able to do a printf through STDOUT (or another file pointer) TO the database via a
PQexec call of COPY. Something like this would be ideal:
PQexec(conn, "COPY moncoverage from STDOUT");
I have been unable to figure out if this is possible. I understand that I can do this via stdin,
but I don't want the user to make the entry, I want the executable to do it and still enjoy the
performance of the COPY command.
I also understand that I can open a pipe to psql and do it through there like this:
FILE *ofp = popen("psql -a -c 'COPY tablename from stdin' -d dbname -h host","w");
for(i=0;i<15000;i++)
fprintf(ofp,"%s\n",row[i]);
fprintf(ofp,"\\.\n");
pclose(ofp);
However, performance is extremely important to me in this application. I already have a connection
open to the db in the C executable to do 10 inserts, so it I would like to go ahead and use that
connection to perform my PQexec(conn,'COPY...') to reduce connection overhead. Also, I am assuming that
the PQexec call makes a more efficient connection that the popen to psql and COPY scheme. During trial
runs my server maintains 34 postmaster processes -- there has to be a better way to do this.
Any help would be greatly appreciated. Please let me know if this is the wrong place to post this.
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: libpq PQexec call of COPY
@ 2001-04-10 17:08 Peter Eisentraut <peter_e@gmx.net>
parent: John Coers <coers@intrinsity.com>
0 siblings, 0 replies; 2+ messages in thread
From: Peter Eisentraut @ 2001-04-10 17:08 UTC (permalink / raw)
To: John Coers <coers@intrinsity.com>; +Cc: pgsql-hackers@postgresql.org
John Coers writes:
> Hi,
>
> My generic problem is performance when copying very large amounts of data to a db from multiple clients.
>
> I am writing a C program on Linux Redhat6.2 that accesses a 7.0.3 database using libpq. I
> would like to be able to do a printf through STDOUT (or another file pointer) TO the database via a
> PQexec call of COPY. Something like this would be ideal:
>
> PQexec(conn, "COPY moncoverage from STDOUT");
>
> I have been unable to figure out if this is possible. I understand that I can do this via stdin,
> but I don't want the user to make the entry, I want the executable to do it and still enjoy the
> performance of the COPY command.
Read the libpq chapter in the Programmer's Guide and look into
src/bin/psql/copy.c for information and examples of using COPY through
libpq. Yes, it's possible, but you need to use special API calls.
--
Peter Eisentraut peter_e@gmx.net http://yi.org/peter-e/
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