Change the position of notoptions lookup in get_option

[spacedmonkey]

Added in [4855] and #3726 the notoptions cache was added to get_option. This cache was designed to save database queries, do option name that are none not to exist in the database / cache.

However, the ordering this functions present a performance problem. In get_option the look for if a option does not exist, is done before if it does. It is extremely uncommon for a get_option, for a option name that does not exist. Most times it is called, it for a option that does exist. This means the call to notoptions cache is called pointless.

Moving this check, before the database lookup would improve performance.

Trac ticket: https://core.trac.wordpress.org/ticket/58277

[spacedmonkey]

500 runs on TT1

	Trunk - TT1	PR - TT1	Trunk - TT1 - Memcached	PR - TT1 - Memcached
Response Time (median)	73.16	73.1	73.62	72.49
wp-load-alloptions-query (median)	0.7	0.69	0.68	0.68
wp-before-template (median)	28.21	28.28	28.29	28.04
wp-before-template-db-queries (median)	2.76	2.78	2.76	2.75
wp-template (median)	37.73	37.64	38.11	37.62
wp-total (median)	65.91	66.1	66.63	65.87
wp-template-db-queries (median)	6.29	6.34	6.39	6.37

500 runs on TT3

	Trunk - TT3	PR - TT3	Trunk - TT3 - Memcached	PR - TT3 - Memcached
Response Time (median)	109.18	108.92	108.14	107.78
wp-before-template (median)	58.54	58.76	55.08	54.61
wp-template (median)	44.77	44.6	47.25	47.47
wp-total (median)	103.52	103.45	102.76	102.47

[spacedmonkey]

In a block theme, this saves 100s of calls to cache.

PR - 1302 vs Trunk - 1949.

[spacedmonkey]

Trunk - TT1

[spacedmonkey]

PR - TT1

[azaozz]

Replying to spacedmonkey:

In a block theme, this saves 100s of calls to cache.

Yep, this change makes sense imho. I'm a bit unsure on how to best test the result. Seems it would have to compare getting existing and non-existing options (that would trigger DB connections). Perhaps something like get an existing option 1000 times, and 5 different non-existing options 3 times each, etc.

In any case reducing the number of cache lookups is a good thing, even if the speed improvements are minimal.