Re: BUG #3031: PHP (and others?) cannot close a connection when "in" a COPY-statement

On 20-2-2007 4:42 Tom Lane wrote:
> "Arjen van der Meijden" <acmmailing@tweakers.net> writes:
>> I'm not sure whether this is a php-issue or a postgresql-client-api one, but
>> when connecting gdb to that process and doing a 'bt' it displays:
>> #0  0xa7c36d9f in free () from /lib/tls/libc.so.6
>> #1  0xa7c38c4f in malloc () from /lib/tls/libc.so.6
>> #2  0xa7f58bdb in PQmakeEmptyPGresult () from /usr/lib/libpq.so.5
>> #3  0xa7f59941 in PQgetResult () from /usr/lib/libpq.so.5
>> #4  0x08086fd0 in _close_pgsql_link (rsrc=0x81e42bc) at
>> /usr/src/php-4.4.2/ext/pgsql/pgsql.c:276
>
> Given that stack trace, you'd better complain to the PHP folk.  There is
> no loop in that path in libpq, so the looping must be occurring
> somewhere in the PHP code.

I had a look at that _close_pgsql_link-function and this it the code:

static void _close_pgsql_link(zend_rsrc_list_entry *rsrc TSRMLS_DC)
{
     PGconn *link = (PGconn *)rsrc->ptr;
     PGresult *res;

     while ((res = PQgetResult(link))) {
         PQclear(res);
     }
     PQfinish(link);
     PGG(num_links)--;
}

So there is indeed a very clear loop. But I'm not sure whether this code
is incorrect as a generic "close the connection cleanly without memory
leaks"-function? If I duplicate that while-loop to my c-test code it
indeed keeps getting a non-null/false result from PQgetResult and thus
will loop indefinitely.

Do you know a clean example that displays how to close a link cleanly,
including this COPY-situation? Or can you indicate which commands should
be added to do so? My knowledge of the C-api is very limited, so I don't
know what's wrong here.

Best regards,

Arjen