id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
34681	Optimize memcache_key_warnings()	Adam Johnson	nobody	"The cache functino memcache_key_warnings() iterates the key character-by-character, a slow operation in Python because it has to create and destroy many individual `str` objects. Instead, we can search the string with a regular expression for a 6x speedup.

IPython session comparing old and new approaches:

{{{
In [1]: import re
   ...:
   ...: MEMCACHE_MAX_KEY_LENGTH = 250
   ...:
   ...:
   ...: def old(key):
   ...:     if len(key) > MEMCACHE_MAX_KEY_LENGTH:
   ...:         yield (
   ...:             ""Cache key will cause errors if used with memcached: %r ""
   ...:             ""(longer than %s)"" % (key, MEMCACHE_MAX_KEY_LENGTH)
   ...:         )
   ...:     for char in key:
   ...:         if ord(char) < 33 or ord(char) == 127:
   ...:             yield (
   ...:                 ""Cache key contains characters that will cause errors if ""
   ...:                 ""used with memcached: %r"" % key
   ...:             )
   ...:             break
   ...:
   ...: memcached_error_chars_re = re.compile(r""[\x00-\x32\x127]"")
   ...:
   ...:
   ...: def new(key):
   ...:     if len(key) > MEMCACHE_MAX_KEY_LENGTH:
   ...:         yield (
   ...:             ""Cache key will cause errors if used with memcached: %r ""
   ...:             ""(longer than %s)"" % (key, MEMCACHE_MAX_KEY_LENGTH)
   ...:         )
   ...:     if memcached_error_chars_re.match(key):
   ...:         yield (
   ...:             ""Cache key contains characters that will cause errors if ""
   ...:             ""used with memcached: %r"" % key
   ...:         )
   ...:

In [2]: %timeit list(old('acme-bookstore-user-1234567-book-78910391'))
1.35 µs ± 1.09 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

In [3]: %timeit list(new('acme-bookstore-user-1234567-book-78910391'))
212 ns ± 1.42 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

In [4]: %timeit list(old('homepage\n'))
545 ns ± 1.17 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

In [5]: %timeit list(new('homepage\n'))
209 ns ± 1.03 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)
}}}"	Cleanup/optimization	assigned	Core (Cache system)	dev	Normal				Unreviewed	0	0	0	0	0	0