Thread: PQhost() Returns NULL on Connection
Why would PQhost() return NULL on a valid connection? I would assume that it would return either a host name or Unix domain socket name/path regardless of whether the "host" parameter was passed at connect time. Is it because it won't return a value when a domain socket is used? If so, is there a way to get the domain socket used? Best, Keary Suska Esoteritech, Inc. "Demystifying technology for your home or business"
Keary Suska <hierophant@pcisys.net> writes:
> Why would PQhost() return NULL on a valid connection?
One reason why would be if you'd selected the server by hostaddr rather
than host. Returning a host name in this case would require a DNS
lookup, and since the entire point of the hostaddr feature is to avoid
DNS lookups, I don't think that's a particularly great idea.
These functions are really defined as "give me back the connection
options that were specified", anyway, not "peek inside to see what
values are actually in use". So a NULL for an unspecified option
seems reasonable to me.
regards, tom lane
On Apr 26 02:08, Keary Suska wrote: > If so, is there a way to get the domain socket used? Below is some source code snippet I thought can help you. src/interfaces/libpq/fe-connect.c 777 #ifdef HAVE_UNIX_SOCKETS 778 /* pghostaddr and pghost are NULL, so use Unix domain socket */ 779 node = NULL; 780 hint.ai_family = AF_UNIX; 781 UNIXSOCK_PATH(portstr, portnum, conn->pgunixsocket); 782 #else src/include/libpq/pqcomm.h 77 /* Configure the UNIX socket location for the well known port. */ 78 79 #define UNIXSOCK_PATH(path,port,defpath) \ 80 snprintf(path, sizeof(path), "%s/.s.PGSQL.%d", \ 81 ((defpath) && *(defpath) != '\0') ? (defpath) : \ 82 DEFAULT_PGSOCKET_DIR, \ 83 (port)) Regards.
on 4/26/06 5:59 PM, tgl@sss.pgh.pa.us purportedly said: >> Why would PQhost() return NULL on a valid connection? > > One reason why would be if you'd selected the server by hostaddr rather > than host. Returning a host name in this case would require a DNS > lookup, and since the entire point of the hostaddr feature is to avoid > DNS lookups, I don't think that's a particularly great idea. > > These functions are really defined as "give me back the connection > options that were specified", anyway, not "peek inside to see what > values are actually in use". So a NULL for an unspecified option > seems reasonable to me. I wasn't sure, because the behavior is not consistent. For instance, PQport() will return a value regardless of the connection type and parameters passed to connect. Also, there doesn't appear to be a way to retrieve hostaddr even if specified, so I thought maybe the PQhost() was more generic. E.g. the lib could return an address if specified and not have to do a wasteful DNS lookup. Considering that the connection status functions exist to retrieve parameter values, it would at least be good to have access to all of them, and not just a selection of them. Best, Keary Suska Esoteritech, Inc. "Demystifying technology for your home or business"