Tuesday, May 11, 2010, 8:36:46 PM, you wrote:
JF> On Sun, May 9, 2010 at 4:59 PM, Roel Bruggink <r...@fourdigits.nl> wrote:
>> On Sun, May 9, 2010 at 8:33 PM, Jim Fulton <j...@zope.com> wrote:
>>> Our recent discussion of compression made me curious so I did some
>>> analysis of pickle sizes in one of our large databases. This is for a
>>> content management system. The database is packed weekly. It doesn't
>>> include media, which are in blobs.
>>> There were ~19 million transaction in the database and around 130
>>> million data records. About 60% of the size was taken up by BTrees.
>>> Compressing pickles using zlib with default compression reduced the
>>> pickle sizes by ~58%. The average uncompressed record size was 1163
>>> bytes. The average compressed size was ~493 bytes.
>>> This is probably enough of a savings to make compression interesting.
>> That's really interesting! Did you notice any issues performance wise, or
>> didn't you check that yet?
JF> OK, I did some crude tests. It looks like compressing is a little
JF> less expensive than pickling and decompressing is a little more
JF> expensive than unpickling, which is to say this is pretty cheap. For
JF> example, decompressing a data record took around 20 microseconds on my
JF> machine. A typical ZEO load takes 10s of milliseconds. Even in Shane's
JF> zodb shootout benchmark which loads data from ram, load times are
JF> several hundred microseconds or more.
JF> I don't think compression will hurt performance. It is likeley to
JF> help it in practice because:
JF> - There will be less data to send back and forth to remote servers.
JF> - Smaller databases will get more benefit from disk caches.
JF> (Databases will be more likely to fit on ssds.)
JF> - ZEO caches (and relstorage memcached caches) will be able to hold
JF> more object records.
I was thinking about using other compressors.
I found this:
Seems like gzip/zlib is the fastest with some expense of efficiency.
Adam GROSZER mailto:agros...@gmail.com
Quote of the day:
What this country needs is a good five-cent microcomputer.
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