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, 19 insertions, 31 deletions

diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index b9c52eb50c2..ffd9926dc4e 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -884,38 +884,26 @@ lo_initialize(PGconn *conn)
 	MemSet((char *) lobjfuncs, 0, sizeof(PGlobjfuncs));
 
 	/*
-	 * Execute the query to get all the functions at once.  In 7.3 and later
-	 * we need to be schema-safe.  lo_create only exists in 8.1 and up.
-	 * lo_truncate only exists in 8.3 and up.
+	 * Execute the query to get all the functions at once.  (Not all of them
+	 * may exist in older server versions.)
 	 */
-	if (conn->sversion >= 70300)
-		query = "select proname, oid from pg_catalog.pg_proc "
-			"where proname in ("
-			"'lo_open', "
-			"'lo_close', "
-			"'lo_creat', "
-			"'lo_create', "
-			"'lo_unlink', "
-			"'lo_lseek', "
-			"'lo_lseek64', "
-			"'lo_tell', "
-			"'lo_tell64', "
-			"'lo_truncate', "
-			"'lo_truncate64', "
-			"'loread', "
-			"'lowrite') "
-			"and pronamespace = (select oid from pg_catalog.pg_namespace "
-			"where nspname = 'pg_catalog')";
-	else
-		query = "select proname, oid from pg_proc "
-			"where proname = 'lo_open' "
-			"or proname = 'lo_close' "
-			"or proname = 'lo_creat' "
-			"or proname = 'lo_unlink' "
-			"or proname = 'lo_lseek' "
-			"or proname = 'lo_tell' "
-			"or proname = 'loread' "
-			"or proname = 'lowrite'";
+	query = "select proname, oid from pg_catalog.pg_proc "
+		"where proname in ("
+		"'lo_open', "
+		"'lo_close', "
+		"'lo_creat', "
+		"'lo_create', "
+		"'lo_unlink', "
+		"'lo_lseek', "
+		"'lo_lseek64', "
+		"'lo_tell', "
+		"'lo_tell64', "
+		"'lo_truncate', "
+		"'lo_truncate64', "
+		"'loread', "
+		"'lowrite') "
+		"and pronamespace = (select oid from pg_catalog.pg_namespace "
+		"where nspname = 'pg_catalog')";
 
 	res = PQexec(conn, query);
 	if (res == NULL)