minimize-number-sql-queries.mo.md

[MO] Minimize your number of SQL queries

Owner: Xavier Lefevre

Control points

• you don't lazy load data that you need to access directly

Why

SQL is extremely powerful to retrieve and manipulate big chunks of data, but not powerful if you want to access data 1000 times in a row

Steps

• By default some ORMs lazy load relations: meaning that it will load the model you want but keep references of the relations
  • If you want to access those relations, it will only re-query the database later, in a loop for instance, it might send thousants of queries to retrieve relations
  • By join-loading the main SQL query, you make sure that you retrieve the relation directly, the ORM will join the model and its relations from the main first query
  • Then if you access one of the relation, it will already be available in the response object
  • See an example with SQL Alchemy: http://docs.sqlalchemy.org/en/latest/orm/loading_relationships.html

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TODO

If you fall on this method of operation and want to fill it don't hesitate! It will help others. You ca for instance, look at this article https://medium.com/about-developer-blog/varnish-58c5d8269269 and convert it to a M33 like steps (short steps and check after after each steps) when you use it.

A good MO example: Setup HTTPS on your docker environment

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