On 2016/04/08 22:21, Rushabh Lathia wrote:
On Fri, Apr 8, 2016 at 6:28 PM, Robert Haas <robertmh...@gmail.com
The comment just before the second hunk in the patch says:
* We don't use a PG_TRY block here, so be careful not to
* without releasing the PGresult.
But the patch adds a whole bunch of new things there that seem like
they can error out, like CHECK_FOR_INTERRUPTS(), for example. Isn't
that a problem?
Basically we fetching the PGresult, after the newly added hunk, so there
should not be any problem.
But yes comment is definitely at wrong place.
PFA patch with correction.
I agree with Rushabh. Thanks for updating the patch!
Another thing I'd like to propose to revise the patch is to call
pgfdw_report_error in the newly added hunk, with the clear argument set
to *false*. The PGresult argument is NULL there, so no need to release
Attached is an updated patch.
diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c
index 189f290..8820597 100644
@@ -598,6 +598,26 @@ pgfdw_xact_callback(XactEvent event, void *arg)
/* Assume we might have lost track of prepared statements */
entry->have_error = true;
+ * If we had submitted a command to the remote server using
+ * an asynchronous execution function, the command might
+ * have not yet completed. Check to see if a command is
+ * still being processed by the remote server, and if so,
+ * request cancellation of the command; if not, abort
+ * gracefully.
+ if (PQtransactionStatus(entry->conn) == PQTRANS_ACTIVE)
+ PGcancel *cancel;
+ char errbuf;
+ if ((cancel = PQgetCancel(entry->conn)))
+ PQcancel(cancel, errbuf, sizeof(errbuf));
/* If we're aborting, abort all remote transactions too */
res = PQexec(entry->conn, "ABORT TRANSACTION");
/* Note: can't throw ERROR, it would be infinite loop */
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index ee0220a..0378f1d 100644
@@ -32,6 +32,7 @@
@@ -3131,6 +3132,7 @@ execute_dml_stmt(ForeignScanState *node)
ExprContext *econtext = node->ss.ps.ps_ExprContext;
int numParams = dmstate->numParams;
const char **values = dmstate->param_values;
+ int wc;
* Construct array of query parameter values in text format.
@@ -3147,12 +3149,42 @@ execute_dml_stmt(ForeignScanState *node)
* parameter (see deparse.c), the "inference" is trivial and will produce
* the desired result. This allows us to avoid assuming that the remote
* server has the same OIDs we do for the parameters' types.
+ if (!PQsendQueryParams(dmstate->conn, dmstate->query, numParams,
+ NULL, values, NULL, NULL, 0))
+ pgfdw_report_error(ERROR, NULL, dmstate->conn, false, dmstate->query);
+ * Receive data until PQgetResult is ready to get the result without
+ * blocking.
+ while (PQisBusy(dmstate->conn))
+ /* Sleep until there's something to do */
+ wc = WaitLatchOrSocket(MyLatch,
+ WL_LATCH_SET | WL_SOCKET_READABLE,
+ /* Data available in socket */
+ if (wc & WL_SOCKET_READABLE)
+ if (!PQconsumeInput(dmstate->conn))
+ pgfdw_report_error(ERROR, NULL, dmstate->conn, false,
+ * Get the result
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
- dmstate->result = PQexecParams(dmstate->conn, dmstate->query,
- numParams, NULL, values, NULL, NULL, 0);
+ dmstate->result = PQgetResult(dmstate->conn);
if (PQresultStatus(dmstate->result) !=
(dmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, dmstate->result, dmstate->conn, true,
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