To whom it may concern at Mysql AB:
I see from the Mysql 4.1.1 CHANGELOG that new COMPRESS(), UNCOMPRESS(),
and UNCOMPRESSED_LENGTH() functions were added. That is great news, and
something I have been very interested in for a long time, as evidenced by
this mysql mailing list thread, dating back to 12/18/2001:
http://marc.10east.com/?t=100869803000005&r=1&w=2
The MARC system (marc.10east.com) was one of the primary reasons for me
requesting that this feature be added to Mysql. There is one short-coming
in the new COMPRESS()/UNCOMPRESS() functionality that I would like to
point out, and request that you address.
Here is the background: Anyone that is running a huge system like MARC
that has millions of uncompressed blob records in huge tables, needs to be
able to migrate, in real-time and without down-time, to compressed blobs.
Therefore, we need a way to know if a given field is compressed or not.
Running alter table on our tables, to add an am_i_compressed boolean, not
only takes an excruciating amount of time and resources, but adds bits to
each record that, from a disk-space perspective, we cannot afford.
Instead, I would like to be able to run a query like:
select IFCOMPRESSED(msg_body, UNCOMPRESS(msg_body), msg_body)
from msg_bodies_200402
where <clause>
Note that the IFCOMPRESSED() function is the key, and what I am requesting
be added to future versions of Mysql. That function has to be possible.
Hopefully you are storing a header with your compressed data, and if so,
then the IFCOMPRESSED() is trivial to implement. If you are not storing a
header with your compressed data, then this might be more complicated.
Adding a header might be a possibility -- which is why I am trying to
point this out _EARLY_ in the process before lots of people start using
COMPRESS()/UNCOMPRESS(), or maybe zlib, lzo, or whatever library you are
using can let you know if the data is compressed -- maybe they store a
small header themselves.
Anyway, that is the issue that I want to point out and ask for assistance
on. Thank you very much for listening to the user community and adding
COMPRESS()/UNCOMPRESS(), and please seriously consider this request.
Sincerely,
--
Lester H. Hightower <[EMAIL PROTECTED]>
Chief Technology Officer, 10 East Corp.
p.s. Could someone at Mysql AB update the URL at the bottom of this page,
http://lists.mysql.com/, to point to http://marc.10east.com/ instead of
http://marc.theaimsgroup.com/? That is our old company name, and we are
always trying to reduce usage on that domain name. Thanks.
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