In PQsendQueryStart(), avoid leaking any left-over async result.

Ordinarily there would not be an async result sitting around at this
point, but it appears that in corner cases there can be.  Considering
all the work we're about to launch, it's hardly going to cost anything
noticeable to check.

It's been like this forever, so back-patch to all supported branches.

Report: <CAD-Qf1eLUtBOTPXyFQGW-4eEsop31tVVdZPu4kL9pbQ6tJPO8g@mail.gmail.com>

diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index a9ba54628fd0107b44d6469d972ab878505fa181..87ff5659ff35ef63081af161e9e850cacbdfedb9 100644 (file)
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1386,8 +1386,7 @@ PQsendQueryStart(PGconn *conn)
        }
 
        /* initialize async result-accumulation state */
-       conn->result = NULL;
-       conn->next_result = NULL;
+       pqClearAsyncResult(conn);
 
        /* reset single-row processing mode */
        conn->singleRowMode = false;