A very interesting feature of the SQL Server and PostgreSQL databases (and some others, including SQLite) is the partial index (sometimes also called "filtered index"). That's an index that contains only "parts" of the table data. For instance, we can write the following index in SQL Server and PostgreSQL: CREATE INDEX i ON message WHERE … Continue reading How to Emulate Partial Indexes in Oracle
I keep encountering situations where RDBMS users think that one second for query execution is anything near fast. Most recently, in this Stack Overflow question: Hibernate SQL In clause making CPU usage to 100% The poster's original question was why a similar query executes in one second when executed in SQL Server Management Studio whereas … Continue reading Do Not Think That One Second is Fast for Query Execution
Recently, at the office: Bob: I've looked into that slow query you've told me about yesterday, Alice. I've added the indexes you wanted. Everything should be fine now Alice: Thanks Bob. I'll quickly check ... Nope Bob, still slow, it didn't seem to work Bob: You're right Alice! It looks like Oracle isn't picking up … Continue reading The Index You’ve Added is Useless. Why?