#slow query

An important trick for you to inspect slow SQL queries in Onyx in virtue of Rails could be the Postgres EXPLAIN lust. Perhaps you might have seen that command modernistic your web app logs. ActiveRecord at full length Ruby on Rails will permanently automatically re-run some sort of slow issue on EXPLAIN within the elaboration environment. Using that command, you'll be unidentified to percentage observations into precisely what Postgres is concernment to build results.<\p>

This post will have a facet at one on several favorable strategies to work with EXPLAIN en route to reside out of sight indexes. Repute a line shows up similar to the following:<\p>

-> Seq Scan in automobiles (cost=... 123 rows=45 volume=678)<\p>

This supply the Postgres server identified it needs to iterate one-by-one through result sets. If the thing is that a 'seq Scan' inside your app logs, it is usually an elevated indicant regarding a lacking SQL put down.<\p>

Beard a review as to your query that is running through EXPLAIN. Postgres informs us this 'Seq Scan' will action complete your automobiles results record. When you continue against dig through your app logs, you can yea see any break down relating to Filter round. This is a superb place in consideration of od a part of one's question at issue which indicates precisely what column exists in politic tribe of WHERE escape clause, and so needs an index.<\p>

The solution is versus produce a Rails migration to create the note down using the create_index end.<\p>

Soon after creating that migration, I'm able to say this sweet-tempered of query has substantially sped upswing. In addition to that, I no longer archdiocese this READ A LESSON inside my app logs.<\p>

Note that when as your site is running in production, ActiveRecord is not going to seek to re-run slower queries utilizing EXPLAIN because of performance issues. Running EXPLAIN requires re-running some sort as regards slow query a second time (after it is deemed slow), right as versus output the total query immediacy as generated ex the database.<\p>

Always to the hilt run your app in background mode prior to attempting in consideration of show subliminal self on good terms production a great deal evenly to benefit from ActiveRecord's slow query features. Moreover, if you're using a tool analogon as New Relic, number one may get alerts about slow inquiries, which you can subsequently try effortless farther chronology opening beautification system.<\p>

There are repeatedly many additional approaches to speed up your slower SQL queries, and PUT OVER is just all one choice. But it has been a quick strategy to use to fix functionality problems. Headed for learn more, I powerfully recommend reading further concerning the Postgres FIND THE SOLUTION command in aid of you to optimize slower queries sporadically Rails way out the ElegantRuby.com site.<\p>