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diff --git a/doc/development/understanding_explain_plans.md b/doc/development/understanding_explain_plans.md index 01a0044f096..bfbb7be70e3 100644 --- a/doc/development/understanding_explain_plans.md +++ b/doc/development/understanding_explain_plans.md @@ -80,8 +80,9 @@ Planning time: 2.861 ms Execution time: 3428.596 ms ``` -For more information, refer to the official [EXPLAIN -documentation](https://www.postgresql.org/docs/current/static/sql-explain.html). +For more information, refer to the official +[`EXPLAIN` documentation](https://www.postgresql.org/docs/current/sql-explain.html) +and [using `EXPLAIN` guide](https://www.postgresql.org/docs/current/using-explain.html). ## Nodes @@ -653,9 +654,39 @@ and related tools such as: - <https://explain.depesz.com/> - <http://tatiyants.com/postgres-query-plan-visualization/> -GitLab employees can also use our chatops solution, available in Slack using the -`/chatops` slash command. You can use chatops to get a query plan by running the -following: + +## Producing query plans + +There are a few ways to get the output of a query plan. Of course you +can directly run the `EXPLAIN` query in the `psql` console, or you can +follow one of the other options below. + +### Rails console + +Using the [`activerecord-explain-analyze`](https://github.com/6/activerecord-explain-analyze) +you can directly generate the query plan from the Rails console: + +```ruby +pry(main)> require 'activerecord-explain-analyze' +=> true +pry(main)> Project.where('build_timeout > ?', 3600).explain(analyze: true) + Project Load (1.9ms) SELECT "projects".* FROM "projects" WHERE (build_timeout > 3600) + ↳ (pry):12 +=> EXPLAIN for: SELECT "projects".* FROM "projects" WHERE (build_timeout > 3600) +Seq Scan on public.projects (cost=0.00..2.17 rows=1 width=742) (actual time=0.040..0.041 rows=0 loops=1) + Output: id, name, path, description, created_at, updated_at, creator_id, namespace_id, ... + Filter: (projects.build_timeout > 3600) + Rows Removed by Filter: 14 + Buffers: shared hit=2 +Planning time: 0.411 ms +Execution time: 0.113 ms +``` + +### Chatops + +[GitLab employees can also use our chatops solution, available in Slack using the +`/chatops` slash command](chatops_on_gitlabcom.md). +You can use chatops to get a query plan by running the following: ``` /chatops run explain SELECT COUNT(*) FROM projects WHERE visibility_level IN (0, 20) @@ -674,3 +705,9 @@ For more information about the available options, run: ``` /chatops run explain --help ``` + +## Further reading + +A more extensive guide on understanding query plans can be found in +the [presentation](https://www.dalibo.org/_media/understanding_explain.pdf) +from [Dalibo.org](https://www.dalibo.org/en/). |