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 dcb227a7ace75d214d543116c01ddb7089155e5a..a7f9379d97654d85c08e7b9b268a3edea2c58400 100644 (file)
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -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)
                {