From c91ff03a06443ed88529026ad33464addbf3444d Mon Sep 17 00:00:00 2001
From: Magnus Hagander <magnus@hagander.net>
Date: Wed, 20 Aug 2008 11:53:45 +0000
Subject: [PATCH] Make libpq on windows not try to send chunks larger than
 64Kb.

Per Microsoft knowledge base article Q201213, early versions of
Windows fail when we do this. Later versions of Windows appear
to have a higher limit than 64Kb, but do still fail on large
sends, so we unconditionally limit it for all versions.

Patch from Tom Lane.
---
 src/interfaces/libpq/fe-misc.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 33c704b519..cc3e758ef2 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -23,7 +23,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-misc.c,v 1.134 2008/05/29 22:02:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-misc.c,v 1.135 2008/08/20 11:53:45 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -752,7 +752,16 @@ pqSendSome(PGconn *conn, int len)
 		int			sent;
 		char		sebuf[256];
 
+#ifndef WIN32
 		sent = pqsecure_write(conn, ptr, len);
+#else
+		/*
+		 * Windows can fail on large sends, per KB article Q201213. The failure-point
+		 * appears to be different in different versions of Windows, but 64k should
+		 * always be safe.
+		 */
+		sent = pqsecure_write(conn, ptr, Min(len, 65536));
+#endif
 
 		if (sent < 0)
 		{