Hi,
I found following item in the Developer FAQ.
I don't see why this is related to developers.
------------------------------------------------------------------------------------Why aren't there more compression
optionswhen dumping tables?
pg_dump's built-in compression method is gzip. The primary alternative, bzip2, is normally far too slow to be useful
whendumping large tables.
The two main alternatives regularly proposed for better built-in compression at good speeds are LZO and LZMA/LZMA2/XZ.
LZOis released under the GPL, incompatible with PostgreSQL. The LZMA2 code has been released into the public domain,
butthe C port is a secondary one (C++ is the main development focus) whose code quality hasn't seemed appropriate for
thisproject. And this whole area has traditionally been filled with patent issues that go beyond just the restrictions
ofthe software license.
Another limitation on changing this is that pg_dump output is intended to be archivable, so we had better be prepared
tosupport compression methods for a very long time. The "latest and greatest" compression method is exactly what we
*don't*want.
See the archives for an idea what characteristics an alternate compression tool would need to have in order to be
consideredfor use in core PostgreSQL.
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Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp