Remove server and libpq support for old FE/BE protocol version 2.

Protocol version 3 was introduced in PostgreSQL 7.4. There shouldn't be
many clients or servers left out there without version 3 support. But as
a courtesy, I kept just enough of the old protocol support that we can
still send the "unsupported protocol version" error in v2 format, so that
old clients can display the message properly. Likewise, libpq still
understands v2 ErrorResponse messages when establishing a connection.

The impetus to do this now is that I'm working on a patch to COPY
FROM, to always prefetch some data. We cannot do that safely with the
old protocol, because it requires parsing the input one byte at a time
to detect the end-of-copy marker.

Reviewed-by: Tom Lane, Alvaro Herrera, John Naylor
Discussion: https://www.postgresql.org/message-id/9ec25819-0a8a-d51a-17dc-4150bb3cca3b%40iki.fi

1 files changed, 29 insertions, 98 deletions

diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c
index e04ec1e331b..46155015cfd 100644
--- a/src/backend/commands/copyto.c
+++ b/src/backend/commands/copyto.c
@@ -50,8 +50,7 @@
 typedef enum CopyDest
 {
 	COPY_FILE,					/* to file (or a piped program) */
-	COPY_OLD_FE,				/* to frontend (2.0 protocol) */
-	COPY_NEW_FE,				/* to frontend (3.0 protocol) */
+	COPY_FRONTEND,				/* to frontend */
 } CopyDest;
 
 /*
@@ -116,7 +115,6 @@ static const char BinarySignature[11] = "PGCOPY\n\377\r\n\0";
 /* non-export function prototypes */
 static void EndCopy(CopyToState cstate);
 static void ClosePipeToProgram(CopyToState cstate);
-static uint64 CopyTo(CopyToState cstate);
 static void CopyOneRowTo(CopyToState cstate, TupleTableSlot *slot);
 static void CopyAttributeOutText(CopyToState cstate, char *string);
 static void CopyAttributeOutCSV(CopyToState cstate, char *string,
@@ -140,53 +138,27 @@ static void CopySendInt16(CopyToState cstate, int16 val);
 static void
 SendCopyBegin(CopyToState cstate)
 {
-	if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
-	{
-		/* new way */
-		StringInfoData buf;
-		int			natts = list_length(cstate->attnumlist);
-		int16		format = (cstate->opts.binary ? 1 : 0);
-		int			i;
-
-		pq_beginmessage(&buf, 'H');
-		pq_sendbyte(&buf, format);	/* overall format */
-		pq_sendint16(&buf, natts);
-		for (i = 0; i < natts; i++)
-			pq_sendint16(&buf, format); /* per-column formats */
-		pq_endmessage(&buf);
-		cstate->copy_dest = COPY_NEW_FE;
-	}
-	else
-	{
-		/* old way */
-		if (cstate->opts.binary)
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("COPY BINARY is not supported to stdout or from stdin")));
-		pq_putemptymessage('H');
-		/* grottiness needed for old COPY OUT protocol */
-		pq_startcopyout();
-		cstate->copy_dest = COPY_OLD_FE;
-	}
+	StringInfoData buf;
+	int			natts = list_length(cstate->attnumlist);
+	int16		format = (cstate->opts.binary ? 1 : 0);
+	int			i;
+
+	pq_beginmessage(&buf, 'H');
+	pq_sendbyte(&buf, format);	/* overall format */
+	pq_sendint16(&buf, natts);
+	for (i = 0; i < natts; i++)
+		pq_sendint16(&buf, format); /* per-column formats */
+	pq_endmessage(&buf);
+	cstate->copy_dest = COPY_FRONTEND;
 }
 
 static void
 SendCopyEnd(CopyToState cstate)
 {
-	if (cstate->copy_dest == COPY_NEW_FE)
-	{
-		/* Shouldn't have any unsent data */
-		Assert(cstate->fe_msgbuf->len == 0);
-		/* Send Copy Done message */
-		pq_putemptymessage('c');
-	}
-	else
-	{
-		CopySendData(cstate, "\\.", 2);
-		/* Need to flush out the trailer (this also appends a newline) */
-		CopySendEndOfRow(cstate);
-		pq_endcopyout(false);
-	}
+	/* Shouldn't have any unsent data */
+	Assert(cstate->fe_msgbuf->len == 0);
+	/* Send Copy Done message */
+	pq_putemptymessage('c');
 }
 
 /*----------
@@ -268,20 +240,7 @@ CopySendEndOfRow(CopyToState cstate)
 							 errmsg("could not write to COPY file: %m")));
 			}
 			break;
-		case COPY_OLD_FE:
-			/* The FE/BE protocol uses \n as newline for all platforms */
-			if (!cstate->opts.binary)
-				CopySendChar(cstate, '\n');
-
-			if (pq_putbytes(fe_msgbuf->data, fe_msgbuf->len))
-			{
-				/* no hope of recovering connection sync, so FATAL */
-				ereport(FATAL,
-						(errcode(ERRCODE_CONNECTION_FAILURE),
-						 errmsg("connection lost during COPY to stdout")));
-			}
-			break;
-		case COPY_NEW_FE:
+		case COPY_FRONTEND:
 			/* The FE/BE protocol uses \n as newline for all platforms */
 			if (!cstate->opts.binary)
 				CopySendChar(cstate, '\n');
@@ -780,42 +739,6 @@ BeginCopyTo(ParseState *pstate,
 }
 
 /*
- * This intermediate routine exists mainly to localize the effects of setjmp
- * so we don't need to plaster a lot of variables with "volatile".
- */
-uint64
-DoCopyTo(CopyToState cstate)
-{
-	bool		pipe = (cstate->filename == NULL);
-	bool		fe_copy = (pipe && whereToSendOutput == DestRemote);
-	uint64		processed;
-
-	PG_TRY();
-	{
-		if (fe_copy)
-			SendCopyBegin(cstate);
-
-		processed = CopyTo(cstate);
-
-		if (fe_copy)
-			SendCopyEnd(cstate);
-	}
-	PG_CATCH();
-	{
-		/*
-		 * Make sure we turn off old-style COPY OUT mode upon error. It is
-		 * okay to do this in all cases, since it does nothing if the mode is
-		 * not on.
-		 */
-		pq_endcopyout(true);
-		PG_RE_THROW();
-	}
-	PG_END_TRY();
-
-	return processed;
-}
-
-/*
  * Clean up storage and release resources for COPY TO.
  */
 void
@@ -837,14 +760,19 @@ EndCopyTo(CopyToState cstate)
 /*
  * Copy from relation or query TO file.
  */
-static uint64
-CopyTo(CopyToState cstate)
+uint64
+DoCopyTo(CopyToState cstate)
 {
+	bool		pipe = (cstate->filename == NULL);
+	bool		fe_copy = (pipe && whereToSendOutput == DestRemote);
 	TupleDesc	tupDesc;
 	int			num_phys_attrs;
 	ListCell   *cur;
 	uint64		processed;
 
+	if (fe_copy)
+		SendCopyBegin(cstate);
+
 	if (cstate->rel)
 		tupDesc = RelationGetDescr(cstate->rel);
 	else
@@ -977,11 +905,14 @@ CopyTo(CopyToState cstate)
 
 	MemoryContextDelete(cstate->rowcontext);
 
+	if (fe_copy)
+		SendCopyEnd(cstate);
+
 	return processed;
 }
 
 /*
- * Emit one row during CopyTo().
+ * Emit one row during DoCopyTo().
  */
 static void
 CopyOneRowTo(CopyToState cstate, TupleTableSlot *slot)