Question : Server Characteristics Total system RAM: 8GB (running MySQL + other stuff than MySQL on it i.e. not dedicated […]
Category: Database Optimization
How to count selectivity rows in PostgreSQL 8.2
Question : I have problem with two queries on PostgreSQL v8.2. It seem like the optimizer chooses a wrong index: […]
Help with query performance using multiple joins
Question : I am struggling with a query performance problem that exceeds my meager DBA skills. I am querying a […]
How to avoid index_merge in a query?
Question : I have multiple queries using index_merge but for put an example, I show you the following query EXPLAIN […]
“Warnings: Operation caused residual I/O” versus key lookups
Question : I’ve seen this warning in SQL Server 2017 execution plans: Warnings: Operation caused residual IO [sic]. The actual […]
Single query to get only newest entry of grouped redundant entries
Question : A table files looks like: id, file_name, vendor_id, created 1, z.txt, 2, 2011 2, z.txt, 2, 2011 3, […]
Logical optimization of joins and selections
Question : I am studying query optimization. I have read that it might be preferred to apply relational selections before […]
Using the database engine tuning advisor – how do I generate the scripts for the recommendations?
Question : I have run a server-side profile trace for over an hour to produce a .trc file with all […]
Do cross-joins get optimised by the client library?
Question : Note This is deliberately database agnostic, I’m interested in how different implementations, er, differ. I came across Joins […]
XML Large DataBase is the best? [closed]
Question : It’s difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or […]