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phorge-phorge/resources/sql/patches/20121220.generalcache.sql
epriestley aae5f9efd3 Implement a more compact, general database-backed key-value cache
Summary:
See discussion in D4204. Facebook currently has a 314MB remarkup cache with a 55MB index, which is slow to access. Under the theory that this is an index size/quality problem (the current index is on a potentially-384-byte field, with many keys sharing prefixes), provide a more general index with fancy new features:

  - It implements PhutilKeyValueCache, so it can be a component in cache stacks and supports TTL.
  - It has a 12-byte hash-based key.
  - It automatically compresses large blocks of data (most of what we store is highly-compressible HTML).

Test Plan:
  - Basics:
    - Loaded /paste/, saw caches generate and save.
    - Reloaded /paste/, saw the page hit cache.
  - GC:
    - Ran GC daemon, saw nothing.
    - Set maximum lifetime to 1 second, ran GC daemon, saw it collect the entire cache.
  - Deflate:
    - Selected row formats from the database, saw a mixture of 'raw' and 'deflate' storage.
    - Used profiler to verify that 'deflate' is fast (12 calls @ 220us on my paste list).
  - Ran unit tests

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D4259
2012-12-21 14:17:56 -08:00

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SQL

CREATE TABLE {$NAMESPACE}_cache.cache_general (
id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
cacheKeyHash CHAR(12) BINARY NOT NULL,
cacheKey VARCHAR(128) NOT NULL COLLATE utf8_bin,
cacheFormat VARCHAR(16) NOT NULL COLLATE utf8_bin,
cacheData LONGBLOB NOT NULL,
cacheCreated INT UNSIGNED NOT NULL,
cacheExpires INT UNSIGNED,
KEY `key_cacheCreated` (cacheCreated),
UNIQUE KEY `key_cacheKeyHash` (cacheKeyHash)
) ENGINE=InnoDB, COLLATE utf8_general_ci;