be-fsstubs.c

关系型数据库 Postgresql 6.5.2

/*-------------------------------------------------------------------------
 *
 * be-fsstubs.c
 *	  support for filesystem operations on large objects
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /usr/local/cvsroot/pgsql/src/backend/libpq/be-fsstubs.c,v 1.35 1999/06/04 21:13:38 tgl Exp $
 *
 * NOTES
 *	  This should be moved to a more appropriate place.  It is here
 *	  for lack of a better place.
 *
 *	  Builtin functions for open/close/read/write operations on large objects.
 *
 *	  These functions operate in a private GlobalMemoryContext, which means
 *	  that large object descriptors hang around until we destroy the context.
 *	  That happens in lo_commit().  It'd be possible to prolong the lifetime
 *	  of the context so that LO FDs are good across transactions (for example,
 *	  we could release the context only if we see that no FDs remain open).
 *	  But we'd need additional state in order to do the right thing at the
 *	  end of an aborted transaction.  FDs opened during an aborted xact would
 *	  still need to be closed, since they might not be pointing at valid
 *	  relations at all.  For now, we'll stick with the existing documented
 *	  semantics of LO FDs: they're only good within a transaction.
 *
 *-------------------------------------------------------------------------
 */

#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>

#include <postgres.h>

#include <lib/dllist.h>
#include <libpq/libpq.h>
#include <libpq/libpq-fs.h>
#include <nodes/nodes.h>
#include <utils/memutils.h>
#include <lib/fstack.h>
#include <utils/mcxt.h>
#include <catalog/pg_shadow.h>	/* for superuser() */
#include <storage/fd.h>			/* for O_ */
#include <storage/large_object.h>
#include <libpq/be-fsstubs.h>

/* [PA] is Pascal Andr