![]() ![]() We also use a proxy in between the application and PG. The Ruby on Rails database connection pool. When serving Rails apps with Puma and using Sidekiq, carefully manage the connection pool size and total connections for the database. Production : variables : statement_timeout : 5000 SET statement_timeout = 5000 (in milliseconds) and be displayed like this: SHOW statement_timeout This becomes a session variable which is set like this: In Rails/Active Record, set in config/database.yml under a variables section with a value in milliseconds. checkout_timeout (Rails, default 5s): maximum time Rails will spend trying to check out a connection from the pool before raising an error.Using a connection pool reduces the amount of connection establishment overhead and thus reduces the latency involved with connections, which can increase TPS at a certain scale.Ĭonnection issues could benefit from changing: statement_timeout: The maximum time a statement can execute before it is terminatedĪ connection forks the OS process (creates a new process) and is thus expensive.Partial indexes weigh significantly less, but this article uses pgbench to show how they may benefit SELECT TPS, but negatively impact UPDATE TPS. How Partial Indexes Affect UPDATE Performance in PostgreSQL In our system on our highest write table we had 10 total indexes defined and 6 were classified as Low Scans, High Writes. Remove Seldom Used Indexes on High Write TablesĪs a general rule, if you’re not using an index twice as often as it’s written to, you should probably drop it. Recommends that usually it is safe to delete one of the two. Query that finds duplicate indexes, meaning using the same columns etc. ![]() indexrelid ) DESC Remove Duplicate and Overlapping Indexes indexrelid ) ORDER BY pg_relation_size ( s. indisunique - is not a UNIQUE index AND NOT EXISTS - does not enforce a constraint ( SELECT 1 FROM pg_catalog. indkey ) - no index column is an expression AND NOT i. idx_scan = 0 - has never been scanned AND 0 ALL ( i. indexrelid ) AS index_size FROM pg_catalog. indexrelname AS indexname, pg_relation_size ( s. If an approximate count is acceptable use this: Query: Approximate CountĪ count(*) query on a large table may be too slow. I keep queries in a GitHub repository here: pg_scripts. Using application databases as the data source for a data warehouse or ETL process. OLTP, high quantity of short lived transactions. ![]() My tips operating high scale PostgreSQL databases primarily with Ruby on Rails web applications. PostgreSQL for the Busy MySQL Developer.Automated Daily Backup Solution for PostgreSQL.A Look at PostgreSQL Foreign Key Constraints.Building a Web App with Boring Technologies (2017 Edition).Views, Stored Procedures, and Check Constraints.Bulk Inserts, Returning, and Unlogged Tables.Find Duplicate Records Using ROW_NUMBER Window Function.PGSQL Phriday #001 - Query Stats, Log Tags, and N+1s.PostgreSQL, Ruby on Rails, Rails Guides.Ruby For All Podcast: My Guest Experience □️.PGSQL Phriday #008 - pg_stat_statements, PgHero, Query ID.PGSQL Phriday #009 - Database Change Management. ![]()
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