Question : I have a SELECT query which when running produces the exact same plan in terms of indexes being […]
Why is MySQL using this index? Can I force it to use another?
Question : I have a query, and when I call EXPLAIN for it, it appears that my db is using […]
Is non-dynamic scalar subquery evaluted for each row?
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How to profile the PostgreSQL query planner diagnose what is causing it to take up large amounts of memory and time
Question : I’m fighting with a specific “generated” query (the SQL is generated from a proprietary system, and I won’t […]
Under what circumstances would these 3 queries return different number of results?
Question : Hello I have the following question: Query 1: SELECT b.id, ( SELECT SUM(cb.invoice_amount) AS sum […]
How is the value of row column is estimated in EXPLAIN statement in mysql?
Question : I have the following setup: create table Test(id integer, itemID integer, title varchar(100) ,PRIMARY KEY (id, itemID)); insert […]
Help to understand explain plan in Oracle
Question : I am running a query in some big tables, and although it runs fine even tough is a […]
A MySQL EXPLAIN number of rows discrepancy
Question : MySQL 5.5.49-log More questions on the query in Why does it use temporary? (MySQL) (the query is the […]
SQL Join too slow on postgresql 9.0 vs postgresql 9.1
Question : There is a big difference in execution time, altough the ammount of table data are pretty much the […]
what is “planSummary: IDHACK”?
Question : This Query scans only one document and returns only one document. But this is very slow: 2017-05-22T07:13:24.548+0000 I […]