Question : I am facing an issue with the performance. The selection of data from table is taking more than […]
Category: Query Performance
Do MySQL sub-queries essentially use as much overhead as separate queries?
Question : If I have a query like this: SELECT name FROM ( SELECT * FROM `table` WHERE id IN […]
Getting each status change in a table
Question : I have a table that holds status changes per item. The item can go in and out of […]
Can spatial index help a “range – order by – limit” query
Question : Asking this question, specifically for Postgres, as it has good supoort for R-tree/spatial indexes. We have the following […]
MySQL 5.7 performance issue with 300 GB Innodb [closed]
Question : Closed. This question needs to be more focused. It is not currently accepting answers. Want to improve this […]
Why is PostgreSQL selecting a slow Seq scan when an index scan would be better?
Question : I have the following tables in a Postgres 9.6 DB: create table baseDimensions( id serial not null primary […]
What could be the possible reasons for cardinality estimates being very inaccurate in an execution plan?
Question : I have a query that is selecting some data out of a table. The execution plan shows that […]
Improve Insert performance for 200 Million rows
Question : How can the following insert statement be improved – which varies from 20mins on certain days to 70-140mins […]
Why is LIMIT killing performance of this Postgres query?
Question : I have a Postgres materialized view: Column | Type | Modifiers ———————+——————-+———– document_id | character varying | recorded_date […]
Find missing timestamps grouped by key: finding gaps in my data
Question : I have a table that has a timestamp, some data and a identifying key for the data source: […]