Hello, This this is my first posting to the mailing list.
I am interested in multiple hosts of libpq [1], then I found the bug in this feature. When I set "target_session_attrs" to "any" and call PQsendQuery, my application is succeeded. However, when I set "target_session_attrs" to "read-write" and call PQsendQuery, "another command is already in progress" is occurred. I attached the test application to reproduce this problem. I think this is because PQgetResult is not called until PQgetResult has returned a null pointer. So, I attached the patch for fix this. [1] https://www.postgresql.org/message-id/flat/20150818041850.ga5...@wagner.pp.ru#20150818041850.ga5...@wagner.pp.ru Regards, Daisuke Higuchi
/*
* gcc multiple_hosts_test.c -lpq -I/home/postgres/work/pgsql10/include
-L/home/postgres/work/pgsql10/lib
* if target_session_attrs=read-write, "another command is already in
progress" is occured
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef WIN32
#include <winsock2.h>
#endif
#include "libpq-fe.h"
int main( int argc, char *argv[])
{
int i=0,rtn;
PGconn *conn;
PGresult *r;
const char *keywords[5];
const char *values[5];
/*
** Connect to postgres
*/
keywords[0] = "dbname";
values[0] = "postgres";
keywords[1] = "port";
values[1] = (char *)getenv("PGPORT"); /* export PGPORT=5432,5433 */
keywords[1] = "host";
values[1] = (char *)getenv("PGHOST"); /* export
PGHOST=localhost,localhost */
keywords[2] = "target_session_attrs";
values[2] = "read-write";
keywords[3] = NULL;
values[3] = NULL;
conn = PQconnectdbParams((const char * const*)&keywords, (const char *
const*)&values, 1);
if (PQstatus(conn) != CONNECTION_OK)
{
printf("Connection to database failed: %s
\n",PQerrorMessage(conn));
goto ERR;
}
printf("host=%s,port=%s\n",PQhost(conn),PQport(conn));
/*
** Asynchronous statement
*/
printf("-- SHOW transaction_read_only --\n");
rtn = PQsendQuery(conn, "SHOW transaction_read_only");
if (rtn != 1)
{
printf( "SHOW command failed: %s", PQerrorMessage(conn));
goto ERR;
}
r = PQgetResult(conn);
printf("SHOW transaction_read_only:%s\n",PQgetvalue(r, 0, 0));
r = PQgetResult(conn);
PQclear(r);
/*
** Disconnect
*/
PQfinish(conn);
printf("Success!\n");
return(0);
ERR:
PQfinish(conn);
printf("Failed!\n");
return(1);
}
PQsendQuery_for_target_session_attrs_v1.patch
Description: PQsendQuery_for_target_session_attrs_v1.patch
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