mirror of
https://git.postgresql.org/git/postgresql.git
synced 2024-12-15 08:20:16 +08:00
149 lines
4.0 KiB
Plaintext
149 lines
4.0 KiB
Plaintext
$PostgreSQL: pgsql/contrib/pg_dumplo/README.pg_dumplo,v 1.3 2003/11/29 19:51:35 pgsql Exp $
|
|
|
|
pg_dumplo - PostgreSQL large object dumper
|
|
==========================================
|
|
|
|
By Karel Zak <zakkr@zf.jcu.cz>
|
|
|
|
|
|
Compilation:
|
|
===========
|
|
|
|
* run master ./configure in the PG source top directory
|
|
* gmake all
|
|
* gmake install
|
|
|
|
THANKS:
|
|
======
|
|
|
|
<??? I lost his e-mail ???>
|
|
* option '--all' and pg_class usage
|
|
|
|
Pavel Janík ml. <Pavel.Janik@linux.cz>
|
|
* HOWTO (the rest of this file)
|
|
|
|
|
|
How to use pg_dumplo?
|
|
=====================
|
|
|
|
(c) 2000, Pavel Janík ml. <Pavel.Janik@linux.cz>
|
|
|
|
|
|
Q: How do you use pg_dumplo?
|
|
============================
|
|
|
|
A: This is a small demo of backing up the database table with Large Objects:
|
|
|
|
|
|
We will create a demo database and a small and useless table `lo' inside
|
|
it:
|
|
|
|
SnowWhite:$ createdb test
|
|
CREATE DATABASE
|
|
|
|
Ok, our database with the name 'test' is created. Now we should create demo
|
|
table which will contain only one column with the name 'id' which will hold
|
|
the OID number of a Large Object:
|
|
|
|
SnowWhite:$ psql test
|
|
Welcome to psql, the PostgreSQL interactive terminal.
|
|
|
|
Type: \copyright for distribution terms
|
|
\h for help with SQL commands
|
|
\? for help on internal slash commands
|
|
\g or terminate with semicolon to execute query
|
|
\q to quit
|
|
|
|
test=# CREATE TABLE lo (id oid);
|
|
CREATE
|
|
test=# \lo_import /etc/aliases
|
|
lo_import 19338
|
|
test=# INSERT INTO lo VALUES (19338);
|
|
INSERT 19352 1
|
|
test=# select * from lo;
|
|
id
|
|
-------
|
|
19338
|
|
(1 row)
|
|
|
|
test=# \q
|
|
|
|
In the above example you can see that we have also imported one "Large
|
|
Object" - the file /etc/aliases. It has an oid of 19338 so we have inserted
|
|
this oid number to the database table lo to the column id. The final SELECT
|
|
shows that we have one record in the table.
|
|
|
|
Now we can demonstrate the work of pg_dumplo. We will create a dump directory
|
|
which will contain the whole dump of large objects (/tmp/dump):
|
|
|
|
mkdir -p /tmp/dump
|
|
|
|
Now we can dump all large objects from the database `test' which have OIDs
|
|
stored in the column `id' in the table `lo':
|
|
|
|
SnowWhite:$ pg_dumplo -s /tmp/dump -d test -l lo.id
|
|
pg_dumplo: dump lo.id (1 large obj)
|
|
|
|
Voila, we have the dump of all Large Objects in our directory:
|
|
|
|
SnowWhite:$ tree /tmp/dump/
|
|
/tmp/dump/
|
|
`-- test
|
|
|-- lo
|
|
| `-- id
|
|
| `-- 19338
|
|
`-- lo_dump.index
|
|
|
|
3 directories, 2 files
|
|
SnowWhite:$
|
|
|
|
In practice, we'd probably use
|
|
|
|
SnowWhite:$ pg_dumplo -s /tmp/dump -d test -e
|
|
|
|
to export all large objects that are referenced by any OID-type column
|
|
in the database. Calling out specific column(s) with -l is only needed
|
|
for a selective dump.
|
|
|
|
For routine backup purposes, the dump directory could now be converted into
|
|
an archive file with tar and stored on tape. Notice that a single dump
|
|
directory can hold the dump of multiple databases.
|
|
|
|
Now, how can we recreate the contents of the table lo and the Large Object
|
|
database when something went wrong? To do this, we expect that pg_dump is
|
|
also used to store the definition and contents of the regular tables in
|
|
the database.
|
|
|
|
SnowWhite:$ pg_dump test >test.backup
|
|
|
|
Now, if we lose the database:
|
|
|
|
SnowWhite:$ dropdb test
|
|
DROP DATABASE
|
|
|
|
we can recreate it and reload the regular tables from the dump file:
|
|
|
|
SnowWhite:$ createdb test
|
|
CREATE DATABASE
|
|
|
|
SnowWhite:$ psql test <test.backup
|
|
|
|
But at this point our database has no large objects in it. What's more,
|
|
the large-object-referencing columns contain the OIDs of the old large
|
|
objects, which will not be the OIDs they'll have when reloaded. Never
|
|
fear: pg_dumplo will fix the large object references at the same time
|
|
it reloads the large objects. We reload the LO data from the dump
|
|
directory like this:
|
|
|
|
SnowWhite:$ pg_dumplo -s /tmp/dump -d test -i
|
|
19338 lo id test/lo/id/19338
|
|
SnowWhite:$
|
|
|
|
And this is everything. The contents of table lo will be automatically
|
|
updated to refer to the new large object OIDs.
|
|
|
|
Summary: In this small example we have shown that pg_dumplo can be used to
|
|
completely dump the database's Large Objects very easily.
|
|
|
|
For more information see the help ( pg_dumplo -h ).
|