Calculating MD5 is very fast in GAE:
from time import time
from hashlib import md5
s = '1'*100
t = time()
for i in xrange(100):
md5(s).digest()
print time() - t
result: 1.469063
I remember the key name is limited to 500 bytes long, so it may exceed if
you combine several keys into one.
--
keakon
My blog(Chinese): www.keakon.net
Blog source code: https://bitbucket.org/keakon/doodle/
On Wed, Dec 15, 2010 at 2:43 PM, johnP j...@thinkwave.com wrote:
I need to create a large amount of records which relate three other
entities. Just for example, take 100 people; 100 days; and 100
restaurants. To create a record for an intersection of a person/day/
restaurant, it's possible to create keyname of person.key()+day.key()
+restaurant.key(). And to retrieve records, it's easy to generate a
list of keys and use a db.get().
In the internet somewhere, I read a comment by Nick Johnson saying
that long keynames are inefficient, and that it can be a good idea to
use a MD5 or SHA1 hash function to shorten the key name. My question
is, how expensive are the MD5 and SHA1 functions?
For example, if I need to generate 100 keys for each view (e.g. to
retrieve people who visited 1 restaurant in 1 day, I can generate 100
keys and db.get() that list) - is it cheaper to use the MD5 hash to
keep key_names shorter? Or is the cost of generating the hashes more
than any savings from shortening the keys?
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