RubyLetter - A Rubyist's Guide to Postgresql's Explain

If you want to understand why your database queries maybe aren’t as fast as they used to be, nothing beats a little feature of postgres called explain . It’s a simple idea. Just ask postgres to explain how it plans to perform a query and it’ll tell you. You can even have it execute the query it and compare expected performance to actual. Sound familiar? You may have seen explain before. Ever sinc

[makky55makky55]

ActiveRecord で最後に .explain を付けるとそのまま EXPLAIN を実行できるのか。いちいちActiveRecordを実行してログに出ていたSQLをSQLツールで実行しなくてすむので便利だな。

[mooonymann]

“I find myself using “Rows” the most. It’s really useful for seeing if the query scales. If it equals “1” then I know the query is performant. If it equals the number of records in the table, then the query probably isn’t very performant with large datasets.”