Optimize the code inside AR::QueryCache middleware #32414
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eugeneius
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Apr 2, 2018
| end | ||
| ActiveRecord::Base.connection_handler.connection_pool_list.select do |pool| | ||
| unless pool.query_cache_enabled | ||
| pool.enable_query_cache! |
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ConnectionPool#enable_query_cache! returns nil when there's no active connection:
The query cache will be enabled but the pool won't be returned, so the complete hook won't disable it... which will cause a regression of #26666 🐛
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It's probably clearer to find the connection pools and enable the query cache on them as separate steps:
ActiveRecord::Base.connection_handler.connection_pool_list
.reject(&:query_cache_enabled).each(&:enable_query_cache!)Could you update this test to assert that the query cache is disabled afterwards too?
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eugeneius
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| pool.disable_query_cache! unless caching_was_enabled | ||
| end | ||
| def self.complete(pools) | ||
| pools.each {|pool| pool.disable_query_cache! } |
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RuboCop wants a space after the opening brace here.
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eugeneius
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Optimize the code inside AR::QueryCache middleware
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Summary
Reduce number of generated arrays from n+1 to 1 where n is the number of pools.
It can be important for applications that use a techniques like database sharding and can have a hundred of databases used by the same app.
In my project we use 6: 1 primary and 2 shards + a slave for each of them.
Follow up on #28869 (comment)
r? @matthewd
cc @eugeneius