Re: [HACKERS] PATCH: Batch/pipelining support for libpq

    Vaishnavi Prabakaran wrote:

> Yes, I have created a new patch entry into the commitfest 2017-03 and
> attached the latest patch with this e-mail.

Please find attached a companion patch implementing the batch API in
pgbench, exposed as \beginbatch and \endbatch meta-commands
(without documentation).

The idea for now is to make it easier to exercise the API and test
how batching performs. I guess I'll submit the patch separately in
a future CF, depending on when/if the libpq patch goes in.

While developing this, I noted a few things with 0001-v4:

1. lack of initialization for count in PQbatchQueueCount.
Trivial fix:

--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1874,7 +1874,7 @@ PQisBusy(PGconn *conn)
 int
 PQbatchQueueCount(PGconn *conn)
 {
-    int            count;
+    int            count = 0;
    PGcommandQueueEntry *entry;

2. misleading error message in PQexecStart. It gets called by a few other
functions than PQexec, such as PQprepare. As I understand it, the intent
here is to forbid the synchronous functions in batch mode, so this error
message should not single out PQexec.

@@ -1932,6 +2425,13 @@ PQexecStart(PGconn *conn)
    if (!conn)
        return false;

+    if (conn->asyncStatus == PGASYNC_QUEUED || conn->batch_status !=
PQBATCH_MODE_OFF)
+    {
+        printfPQExpBuffer(&conn->errorMessage,
+                          libpq_gettext("cannot
PQexec in batch mode\n"));
+        return false;
+    }
+

3. In relation to #2, PQsendQuery() is not forbidden in batch mode
although I don't think it can work with it, as it's based on the old
protocol.


Best regards,
--
Daniel Vérité
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Twitter: @DanielVerite

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