libpq failed to cope with COPY FROM STDIN if the command was issued

via extended query protocol, because it sends Sync right after Execute
without realizing that the command to be executed is COPY.  There seems
to be no reasonable way for it to realize that, either, so the best fix
seems to be to make the backend ignore Sync during copy-in mode.  Bit of
a wart on the protocol, but little alternative.  Also, libpq must send
another Sync after terminating the COPY, if the command was issued via
Execute.

Author: tglsfdc

doc/src/sgml/protocol.sgml

@@ -1,4 +1,4 @@
-<!-- $Header: /cvsroot/pgsql/doc/src/sgml/protocol.sgml,v 1.39 2003/06/27 19:08:37 tgl Exp $ -->
+<!-- $Header: /cvsroot/pgsql/doc/src/sgml/protocol.sgml,v 1.40 2003/08/13 18:56:21 tgl Exp $ -->
 
 <chapter id="protocol">
  <title>Frontend/Backend Protocol</title>
@@ -919,8 +919,7 @@
 
    <para>
     In the event of a backend-detected error during copy-in mode (including
-    receipt of a CopyFail message, or indeed any frontend message other than
-    CopyData or CopyDone), the backend will issue an ErrorResponse 
+    receipt of a CopyFail message), the backend will issue an ErrorResponse 
     message.  If the <command>COPY</> command was issued via an extended-query
     message, the backend will now discard frontend messages until a Sync
     message is received, then it will issue ReadyForQuery and return to normal
@@ -930,6 +929,15 @@
     messages issued by the frontend will simply be dropped.
    </para>
 
+   <para>
+    The backend will ignore Flush and Sync messages received during copy-in
+    mode.  Receipt of any other non-copy message type constitutes an error
+    that will abort the copy-in state as described above.  (The exception for
+    Flush and Sync is for the convenience of client libraries that always
+    send Flush or Sync after an Execute message, without checking whether
+    the command to be executed is a <command>COPY FROM STDIN</>.)
+   </para>
+
    <para>
     Copy-out mode (data transfer from the server) is initiated when the
     backend executes a <command>COPY TO STDOUT</> SQL statement.  The backend

src/backend/commands/copy.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.208 2003/08/08 21:41:30 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.209 2003/08/13 18:56:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -386,6 +386,7 @@ CopyGetData(void *databuf, int datasize)
 					/* Try to receive another message */
 					int			mtype;
 
+				readmessage:
 					mtype = pq_getbyte();
 					if (mtype == EOF)
 						ereport(ERROR,
@@ -409,6 +410,15 @@ CopyGetData(void *databuf, int datasize)
 									 errmsg("COPY from stdin failed: %s",
 										 pq_getmsgstring(copy_msgbuf))));
 							break;
+						case 'H':		/* Flush */
+						case 'S':		/* Sync */
+							/*
+							 * Ignore Flush/Sync for the convenience of
+							 * client libraries (such as libpq) that may
+							 * send those without noticing that the command
+							 * they just sent was COPY.
+							 */
+							goto readmessage;
 						default:
 							ereport(ERROR,
 									(errcode(ERRCODE_PROTOCOL_VIOLATION),

src/interfaces/libpq/fe-exec.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.144 2003/08/13 16:29:03 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.145 2003/08/13 18:56:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -647,6 +647,9 @@ PQsendQuery(PGconn *conn, const char *query)
 		return 0;
 	}
 
+	/* remember we are using simple query protocol */
+	conn->ext_query = false;
+
 	/*
 	 * Give the data a push.  In nonblock mode, don't complain if we're
 	 * unable to send it all; PQgetResult() will do any additional
@@ -901,6 +904,9 @@ PQsendQueryGuts(PGconn *conn,
 		pqPutMsgEnd(conn) < 0)
 		goto sendFailed;
 
+	/* remember we are using extended query protocol */
+	conn->ext_query = true;
+
 	/*
 	 * Give the data a push.  In nonblock mode, don't complain if we're
 	 * unable to send it all; PQgetResult() will do any additional
@@ -1187,29 +1193,28 @@ PQexecStart(PGconn *conn)
 	 */
 	while ((result = PQgetResult(conn)) != NULL)
 	{
-		if (result->resultStatus == PGRES_COPY_IN)
+		ExecStatusType resultStatus = result->resultStatus;
+
+		PQclear(result);		/* only need its status */
+		if (resultStatus == PGRES_COPY_IN)
 		{
 			if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
 			{
 				/* In protocol 3, we can get out of a COPY IN state */
 				if (PQputCopyEnd(conn,
 					 libpq_gettext("COPY terminated by new PQexec")) < 0)
-				{
-					PQclear(result);
 					return false;
-				}
 				/* keep waiting to swallow the copy's failure message */
 			}
 			else
 			{
 				/* In older protocols we have to punt */
-				PQclear(result);
 				printfPQExpBuffer(&conn->errorMessage,
 								  libpq_gettext("COPY IN state must be terminated first\n"));
 				return false;
 			}
 		}
-		else if (result->resultStatus == PGRES_COPY_OUT)
+		else if (resultStatus == PGRES_COPY_OUT)
 		{
 			if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
 			{
@@ -1224,13 +1229,11 @@ PQexecStart(PGconn *conn)
 			else
 			{
 				/* In older protocols we have to punt */
-				PQclear(result);
 				printfPQExpBuffer(&conn->errorMessage,
 								  libpq_gettext("COPY OUT state must be terminated first\n"));
 				return false;
 			}
 		}
-		PQclear(result);
 	}
 
 	/* OK to send a command */
@@ -1409,6 +1412,16 @@ PQputCopyEnd(PGconn *conn, const char *errormsg)
 				pqPutMsgEnd(conn) < 0)
 				return -1;
 		}
+		/*
+		 * If we sent the COPY command in extended-query mode, we must
+		 * issue a Sync as well.
+		 */
+		if (conn->ext_query)
+		{
+			if (pqPutMsgStart('S', false, conn) < 0 ||
+				pqPutMsgEnd(conn) < 0)
+				return -1;
+		}
 	}
 	else
 	{
@@ -2055,12 +2068,15 @@ PQgetisnull(const PGresult *res, int tup_num, int field_num)
 int
 PQsetnonblocking(PGconn *conn, int arg)
 {
+	bool	barg;
+
 	if (!conn || conn->status == CONNECTION_BAD)
 		return -1;
 
-	arg = (arg == TRUE) ? 1 : 0;
+	barg = (arg ? TRUE : FALSE);
+
 	/* early out if the socket is already in the state requested */
-	if (arg == conn->nonblocking)
+	if (barg == conn->nonblocking)
 		return (0);
 
 	/*
@@ -2074,7 +2090,7 @@ PQsetnonblocking(PGconn *conn, int arg)
 	if (pqFlush(conn))
 		return (-1);
 
-	conn->nonblocking = arg;
+	conn->nonblocking = barg;
 
 	return (0);
 }

src/interfaces/libpq/fe-protocol3.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-protocol3.c,v 1.7 2003/08/12 21:34:44 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-protocol3.c,v 1.8 2003/08/13 18:56:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1086,6 +1086,16 @@ pqEndcopy3(PGconn *conn)
 		if (pqPutMsgStart('c', false, conn) < 0 ||
 			pqPutMsgEnd(conn) < 0)
 			return 1;
+		/*
+		 * If we sent the COPY command in extended-query mode, we must
+		 * issue a Sync as well.
+		 */
+		if (conn->ext_query)
+		{
+			if (pqPutMsgStart('S', false, conn) < 0 ||
+				pqPutMsgEnd(conn) < 0)
+				return 1;
+		}
 	}
 
 	/*

src/interfaces/libpq/libpq-int.h

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: libpq-int.h,v 1.80 2003/08/04 02:40:20 momjian Exp $
+ * $Id: libpq-int.h,v 1.81 2003/08/13 18:56:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -262,8 +262,10 @@ struct pg_conn
 	PGAsyncStatusType asyncStatus;
 	PGTransactionStatusType xactStatus;
 	/* note: xactStatus never changes to ACTIVE */
-	int			nonblocking;	/* whether this connection is using a
-								 * blocking socket to the backend or not */
+	bool		nonblocking;	/* whether this connection is using
+								 * nonblock sending semantics */
+	bool		ext_query;		/* was our last query sent with extended
+								 * query protocol? */
 	char		copy_is_binary; /* 1 = copy binary, 0 = copy text */
 	int			copy_already_done;		/* # bytes already returned in
 										 * COPY OUT */