Add API for 64-bit large object access. Now users can access up to

4TB large objects (standard 8KB BLCKSZ case).  For this purpose new
libpq API lo_lseek64, lo_tell64 and lo_truncate64 are added.  Also
corresponding new backend functions lo_lseek64, lo_tell64 and
lo_truncate64 are added. inv_api.c is changed to handle 64-bit
offsets.

Patch contributed by Nozomi Anzai (backend side) and Yugo Nagata
(frontend side, docs, regression tests and example program). Reviewed
by Kohei Kaigai. Committed by Tatsuo Ishii with minor editings.

1 files changed, 99 insertions, 2 deletions

diff --git a/src/backend/libpq/be-fsstubs.c b/src/backend/libpq/be-fsstubs.c
index 6f7e474f675..4bc81ba9f4d 100644
--- a/src/backend/libpq/be-fsstubs.c
+++ b/src/backend/libpq/be-fsstubs.c
@@ -39,6 +39,7 @@
 #include "postgres.h"
 
 #include <fcntl.h>
+#include <limits.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
@@ -216,7 +217,7 @@ lo_lseek(PG_FUNCTION_ARGS)
 	int32		fd = PG_GETARG_INT32(0);
 	int32		offset = PG_GETARG_INT32(1);
 	int32		whence = PG_GETARG_INT32(2);
-	int			status;
+	int64		status;
 
 	if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
 		ereport(ERROR,
@@ -225,9 +226,45 @@ lo_lseek(PG_FUNCTION_ARGS)
 
 	status = inv_seek(cookies[fd], offset, whence);
 
+	if (INT_MAX < status)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_BLOB_OFFSET_OVERFLOW),
+				 errmsg("offset overflow: %d", fd)));
+		PG_RETURN_INT32(-1);
+	}
+
 	PG_RETURN_INT32(status);
 }
 
+
+Datum
+lo_lseek64(PG_FUNCTION_ARGS)
+{
+	int32		fd = PG_GETARG_INT32(0);
+	int64		offset = PG_GETARG_INT64(1);
+	int32		whence = PG_GETARG_INT32(2);
+	MemoryContext currentContext;
+	int64			status;
+
+	if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("invalid large-object descriptor: %d", fd)));
+		PG_RETURN_INT64(-1);
+	}
+
+	Assert(fscxt != NULL);
+	currentContext = MemoryContextSwitchTo(fscxt);
+
+	status = inv_seek(cookies[fd], offset, whence);
+
+	MemoryContextSwitchTo(currentContext);
+
+	PG_RETURN_INT64(status);
+}
+
 Datum
 lo_creat(PG_FUNCTION_ARGS)
 {
@@ -264,13 +301,46 @@ Datum
 lo_tell(PG_FUNCTION_ARGS)
 {
 	int32		fd = PG_GETARG_INT32(0);
+	int64		offset = 0;
+
+	if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("invalid large-object descriptor: %d", fd)));
+
+	offset = inv_tell(cookies[fd]);
+
+	if (INT_MAX < offset)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_BLOB_OFFSET_OVERFLOW),
+				 errmsg("offset overflow: %d", fd)));
+		PG_RETURN_INT32(-1);
+	}
+
+	PG_RETURN_INT32(offset);
+}
+
+
+Datum
+lo_tell64(PG_FUNCTION_ARGS)
+{
+	int32		fd = PG_GETARG_INT32(0);
 
 	if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
+	{
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
 				 errmsg("invalid large-object descriptor: %d", fd)));
+		PG_RETURN_INT64(-1);
+	}
 
-	PG_RETURN_INT32(inv_tell(cookies[fd]));
+	/*
+	 * We assume we do not need to switch contexts for inv_tell. That is
+	 * true for now, but is probably more than this module ought to
+	 * assume...
+	 */
+	PG_RETURN_INT64(inv_tell(cookies[fd]));
 }
 
 Datum
@@ -533,6 +603,33 @@ lo_truncate(PG_FUNCTION_ARGS)
 	PG_RETURN_INT32(0);
 }
 
+Datum
+lo_truncate64(PG_FUNCTION_ARGS)
+{
+	int32		fd = PG_GETARG_INT32(0);
+	int64		len = PG_GETARG_INT64(1);
+
+	if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("invalid large-object descriptor: %d", fd)));
+
+	/* Permission checks */
+	if (!lo_compat_privileges &&
+		pg_largeobject_aclcheck_snapshot(cookies[fd]->id,
+										 GetUserId(),
+										 ACL_UPDATE,
+									   cookies[fd]->snapshot) != ACLCHECK_OK)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for large object %u",
+						cookies[fd]->id)));
+
+	inv_truncate(cookies[fd], len);
+
+	PG_RETURN_INT32(0);
+}
+
 /*
  * AtEOXact_LargeObject -
  *		 prepares large objects for transaction commit