From 1de0a4e00eee2a72c0b5b34892092efcec681f81 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 15 Feb 2017 11:03:30 -0500
Subject: [PATCH] libpq: Make target_session_attrs=read-write consume empty
result.
Otherwise, the leftover empty result can cause problems in some
situations.
Michael Paquier and Ashutosh Bapat, per a report from Higuchi Daisuke
---
src/interfaces/libpq/fe-connect.c | 38 ++++++++++++++++++++++++++++---
src/interfaces/libpq/libpq-fe.h | 4 +++-
2 files changed, 38 insertions(+), 4 deletions(-)
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index c505b661c6b..65b7c31dc03 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1896,6 +1896,7 @@ PQconnectPoll(PGconn *conn)
case CONNECTION_SSL_STARTUP:
case CONNECTION_NEEDED:
case CONNECTION_CHECK_WRITABLE:
+ case CONNECTION_CONSUME:
break;
default:
@@ -2935,6 +2936,34 @@ keep_going: /* We will come back to here until there is
conn->status = CONNECTION_OK;
return PGRES_POLLING_OK;
+ case CONNECTION_CONSUME:
+ {
+ conn->status = CONNECTION_OK;
+ if (!PQconsumeInput(conn))
+ goto error_return;
+
+ if (PQisBusy(conn))
+ {
+ conn->status = CONNECTION_CONSUME;
+ restoreErrorMessage(conn, &savedMessage);
+ return PGRES_POLLING_READING;
+ }
+
+ /*
+ * Call PQgetResult() again to consume NULL result.
+ */
+ res = PQgetResult(conn);
+ if (res != NULL)
+ {
+ PQclear(res);
+ conn->status = CONNECTION_CONSUME;
+ goto keep_going;
+ }
+
+ /* We are open for business! */
+ conn->status = CONNECTION_OK;
+ return PGRES_POLLING_OK;
+ }
case CONNECTION_CHECK_WRITABLE:
{
if (!saveErrorMessage(conn, &savedMessage))
@@ -2994,9 +3023,12 @@ keep_going: /* We will come back to here until there is
/* We can release the address lists now. */
release_all_addrinfo(conn);
- /* We are open for business! */
- conn->status = CONNECTION_OK;
- return PGRES_POLLING_OK;
+ /*
+ * Finish reading any remaining messages before
+ * being considered as ready.
+ */
+ conn->status = CONNECTION_CONSUME;
+ goto keep_going;
}
/*
diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h
index 1b53d0ed16a..635af5b50e3 100644
--- a/src/interfaces/libpq/libpq-fe.h
+++ b/src/interfaces/libpq/libpq-fe.h
@@ -63,8 +63,10 @@ typedef enum
CONNECTION_SETENV, /* Negotiating environment. */
CONNECTION_SSL_STARTUP, /* Negotiating SSL. */
CONNECTION_NEEDED, /* Internal state: connect() needed */
- CONNECTION_CHECK_WRITABLE /* Check if we could make a writable
+ CONNECTION_CHECK_WRITABLE, /* Check if we could make a writable
* connection. */
+ CONNECTION_CONSUME /* Wait for any pending message and
+ * consume them. */
} ConnStatusType;
typedef enum
--
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