我在Heroku中使用Rails 4.2
我对ActiveRecord的includes函数的理解是，它会预先获取所有相关数据，因此以后调用该关系时，不必执行额外的查询。
我看到它获取相关数据，但是在生产环境中（在Heroku上），每次调用该关系时，我也看到它再次获取数据。为什么会这样，我该如何解决？
这仅发生在生产中，而不发生在开发中。
这是我正在观察的功能：
def max_outcome_scores()
scores = Hash.new(0)
logger.info '*** Running max_outcome_score ***'
language_progresses.with_updates.
includes(:progress_marker).find_each do |progress|
scores[progress.progress_marker.topic_id] += progress.progress_marker.weight * ProgressMarker.spread_text.keys.max
end
logger.info '*** Finished max_outcome_score ***'
return scores
end
该功能可以正常工作，但是数据库查询过多。这是我在日志中看到的内容：
2016-07-13T06:55:30.304893+00:00 app[web.1]: *** Running max_outcome_score ***
2016-07-13T06:55:30.308102+00:00 app[web.1]: LanguageProgress Load (2.4ms) SELECT "language_progresses".* FROM "language_progresses" INNER JOIN "progress_updates" ON "progress_updates"."language_progress_id" = "language_progresses"."id" WHERE "language_progresses"."state_language_id" = $1 ORDER BY "language_progresses"."id" ASC LIMIT 1000 [["state_language_id", 209]]
2016-07-13T06:55:30.308882+00:00 app[web.1]: ↳ app/models/state_language.rb:104:in `max_outcome_scores'
2016-07-13T06:55:30.313090+00:00 app[web.1]: CACHE (0.0ms) SELECT "progress_markers".* FROM "progress_markers" WHERE "progress_markers"."id" IN (70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 130, 80, 81, 82, 98, 99, 100, 101, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 83, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 131, 89, 95, 96, 97, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129)
2016-07-13T06:55:30.314067+00:00 app[web.1]: ↳ app/models/state_language.rb:104:in `max_outcome_scores'
2016-07-13T06:55:30.317657+00:00 app[web.1]: CACHE (0.0ms) SELECT "progress_markers".* FROM "progress_markers" WHERE "progress_markers"."id" = $1 LIMIT 1 [["id", 71]]
2016-07-13T06:55:30.318379+00:00 app[web.1]: ↳ app/models/state_language.rb:105:in `block in max_outcome_scores'
2016-07-13T06:55:30.318730+00:00 app[web.1]: CACHE (0.0ms) SELECT "progress_markers".* FROM "progress_markers" WHERE "progress_markers"."id" = $1 LIMIT 1 [["id", 71]]
2016-07-13T06:55:30.319448+00:00 app[web.1]: ↳ app/models/state_language.rb:105:in `block in max_outcome_scores'
2016-07-13T06:55:30.319872+00:00 app[web.1]: CACHE (0.0ms) SELECT "progress_markers".* FROM "progress_markers" WHERE "progress_markers"."id" = $1 LIMIT 1 [["id", 75]]
2016-07-13T06:55:30.320580+00:00 app[web.1]: ↳ app/models/state_language.rb:105:in `block in max_outcome_scores'
2016-07-13T06:55:30.320953+00:00 app[web.1]: CACHE (0.0ms) SELECT "progress_markers".* FROM "progress_markers" WHERE "progress_markers"."id" = $1 LIMIT 1 [["id", 77]]
2016-07-13T06:55:30.321671+00:00 app[web.1]: ↳ app/models/state_language.rb:105:in `block in max_outcome_scores'
2016-07-13T06:55:30.322226+00:00 app[web.1]: CACHE (0.0ms) SELECT "progress_markers".* FROM "progress_markers" WHERE "progress_markers"."id" = $1 LIMIT 1 [["id", 103]]
2016-07-13T06:55:30.322938+00:00 app[web.1]: ↳ app/models/state_language.rb:105:in `block in max_outcome_scores'
2016-07-13T06:55:30.323543+00:00 app[web.1]: CACHE (0.0ms) SELECT "progress_markers".* FROM "progress_markers" WHERE "progress_markers"."id" = $1 LIMIT 1 [["id", 60]]
2016-07-13T06:55:30.324251+00:00 app[web.1]: ↳ app/models/state_language.rb:105:in `block in max_outcome_scores'
2016-07-13T06:55:30.324966+00:00 app[web.1]: *** Finished max_outcome_score ***
我已将日志配置为在生成查询的代码中输出该行。第104行是带有
includes的行，第105行是find-each块内部的行。
最佳答案
事实证明，即使ActiveRecord确实预先收集了所有必要的数据，当要求其提供否则需要去数据库获取的数据时，它仍然会建立相关的查询，而不是使用它，它只是从缓存中提取数据。然后，它记录它构建的查询，但未在数据库上使用。
在某些情况下，看到这些查询可能对测试和调试很有用，但是大多数时候我发现它们只是堵塞了日志。
Raphael提供了一种suppress this logging的方式。将此代码放在config/initializers中的ruby文件中
# Create logger that ignores messages containing “CACHE”
class CacheFreeLogger < ::Logger
def debug(message, *args, &block)
super unless message.include? 'CACHE'
end
end
# Overwrite ActiveRecord’s logger
ActiveRecord::Base.logger = ActiveSupport::TaggedLogging.new(
CacheFreeLogger.new(STDOUT)) unless Rails.env.test?
关于ruby-on-rails - ActiveRecord`includes'不将数据缓存在生产环境中，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38344808/