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.

diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 33c704b5190f9a1e9de835c9525257aedb354c61..cc3e758ef2ecc2f65e183d141c83f80ad3a8111f 100644 (file)
--- 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)
                {