Added documentation about the lo64 support

doc/src/extensions.rst

@@ -47,11 +47,13 @@ functionalities defined by the |DBAPI|_.
 
         Database OID of the object.
 
+
     .. attribute:: mode
 
         The mode the database was open. See `connection.lobject()` for a
         description of the available modes.
 
+
     .. method:: read(bytes=-1)
 
         Read a chunk of data from the current file position. If -1 (default)
@@ -64,6 +66,7 @@ functionalities defined by the |DBAPI|_.
         .. versionchanged:: 2.4
             added Unicode support.
 
+
     .. method:: write(str)
 
         Write a string to the large object. Return the number of bytes
@@ -73,6 +76,7 @@ functionalities defined by the |DBAPI|_.
         .. versionchanged:: 2.4
             added Unicode support.
 
+
     .. method:: export(file_name)
 
         Export the large object content to the file system.
@@ -82,33 +86,50 @@ functionalities defined by the |DBAPI|_.
         .. |lo_export| replace:: `!lo_export()`
         .. _lo_export: http://www.postgresql.org/docs/current/static/lo-interfaces.html#LO-EXPORT
 
+
     .. method:: seek(offset, whence=0)
 
         Set the lobject current position.
 
+        .. versionchanged:: 2.6.0
+            added support for *offset* > 2GB.
+
+
     .. method:: tell()
 
         Return the lobject current position.
 
-    .. method:: truncate(len=0)
-
         .. versionadded:: 2.2.0
 
+        .. versionchanged:: 2.6.0
+            added support for return value > 2GB.
+
+
+    .. method:: truncate(len=0)
+
         Truncate the lobject to the given size.
 
-        The method will only be available if Psycopg has been built against libpq
+        The method will only be available if Psycopg has been built against
-        from PostgreSQL 8.3 or later and can only be used with PostgreSQL servers
+        libpq from PostgreSQL 8.3 or later and can only be used with
-        running these versions. It uses the |lo_truncate|_ libpq function.
+        PostgreSQL servers running these versions. It uses the |lo_truncate|_
+        libpq function.
 
         .. |lo_truncate| replace:: `!lo_truncate()`
         .. _lo_truncate: http://www.postgresql.org/docs/current/static/lo-interfaces.html#LO-TRUNCATE
 
+        .. versionadded:: 2.2.0
+
+        .. versionchanged:: 2.6.0
+            added support for *len* > 2GB.
+
     .. warning::
 
-            If Psycopg is built with |lo_truncate| support (i.e. if the
+        If Psycopg is built with |lo_truncate| support or with the 64 bits API
-            :program:`pg_config` used during setup is version >= 8.3), but at
+        support (resp. from PostgreSQL versions 8.3 and 9.3) but at runtime an
-            runtime an older libpq is found, Psycopg will fail to import.  See
+        older version of the dynamic library is found, the ``psycopg2`` module
-            :ref:`the lo_truncate FAQ <faq-lo_truncate>` about the problem.
+        will fail to import.  See :ref:`the lo_truncate FAQ <faq-lo_truncate>`
+        about the problem.
+
 
     .. method:: close()
 

doc/src/faq.rst

@@ -248,13 +248,20 @@ I can't compile `!psycopg2`: the compiler says *error: libpq-fe.h: No such file
 .. cssclass:: faq
 
 `!psycopg2` raises `!ImportError` with message *_psycopg.so: undefined symbol: lo_truncate* when imported.
-    This means that Psycopg has been compiled with |lo_truncate|_ support,
+    This means that Psycopg was compiled with |lo_truncate|_ support (*i.e.*
-    which means that the libpq used at compile time was version >= 8.3, but at
+    the libpq used at compile time was version >= 8.3) but at runtime an older
-    runtime an older libpq library is found. You can use::
+    libpq dynamic library is found.
+
+    Fast-forward several years, if the message reports *undefined symbol:
+    lo_truncate64* it means that Psycopg was built with large objects 64 bits
+    API support (*i.e.* the libpq used at compile time was at least 9.3) but
+    at runtime an older libpq dynamic library is found.
+
+    You can use::
 
         $ ldd /path/to/packages/psycopg2/_psycopg.so | grep libpq
 
-    to find what is the version used at runtime.
+    to find what is the libpq dynamic library used at runtime.
 
     You can avoid the problem by using the same version of the
     :program:`pg_config` at install time and the libpq at runtime.

doc/src/usage.rst

@@ -899,6 +899,18 @@ using the |lo_import|_ and |lo_export|_ libpq functions.
 .. |lo_export| replace:: `!lo_export()`
 .. _lo_export: http://www.postgresql.org/docs/current/static/lo-interfaces.html#LO-EXPORT
 
+.. versionchanged:: 2.6
+    added support for large objects greated than 2GB. Note that the support is
+    enabled only if both these conditions are verified:
+
+    - the extension was built against libpq at least 9.3 (you can check if
+      `psycopg2.__version__` contains the ``lo64`` flag);
+    - the server version is at least PostgreSQL 9.3
+      (`~connection.server_version` must be >= ``90300``).
+
+    If the contitions are not met several `!lobject` methods will fail if the
+    arguments exceed 2GB.
+
 
 
 .. index::