Обсуждение: pg_dumping large objects

pg_dump --help says:

    -b, --blobs     include large objects in dump

What is the definition of "large object"? Is it a certain set of types
(e.g. text)? Long values stored in these types? What qualifies as
long? In general, how can I tell if I need the -b flag (postgres 7.4).

Morris Goldstein

On Sep 24, 2007, at 12:48 PM, Morris Goldstein wrote:

> pg_dump --help says:
>
>     -b, --blobs     include large objects in dump
>
> What is the definition of "large object"? Is it a certain set of types
> (e.g. text)? Long values stored in these types? What qualifies as
> long? In general, how can I tell if I need the -b flag (postgres 7.4).

The short answer is that if you don't know, you don't need it.  The
longer answer is that large objects are a specialized data type that
allows you store values/datum up to 2GB in size whereas the normal,
behind the scenes TOAST mechanism only handles up to 1GB values.  So,
they are not specialized versions of any other data type, they are
their own, separate data type.

http://www.postgresql.org/docs/8.2/interactive/largeobjects.html

Erik Jones

Software Developer | Emma®
erik@myemma.com
800.595.4401 or 615.292.5888
615.292.0777 (fax)

Emma helps organizations everywhere communicate & market in style.
Visit us online at http://www.myemma.com

Morris Goldstein escribió:
> pg_dump --help says:
>
>     -b, --blobs     include large objects in dump
>
> What is the definition of "large object"?

The kind you create with lo_open(), etc.  If you don't do that, you
don't need it.

--
Alvaro Herrera                        http://www.advogato.org/person/alvherre
"XML!" Exclaimed C++.  "What are you doing here? You're not a programming
language."
"Tell that to the people who use me," said XML.

Large objects are defined in the DDL as type 'OID'.  Those with various drivers may not know the lo_* calls are being used, since in Java this takes place if you use the SQL BLOB type in JDBC and the field itself is defined as 'OID'.

David

Alvaro Herrera wrote:

Morris Goldstein escribió: 

pg_dump --help says:
   -b, --blobs     include large objects in dump

What is the definition of "large object"?   

The kind you create with lo_open(), etc.  If you don't do that, you
don't need it.