Query Engine

Definitions

1. The core component of a database or analytics system responsible for parsing, planning, optimizing, and executing queries against stored data. Query engines like Presto, Apache DataFusion, and DuckDB can often operate independently of the storage layer, querying data in Parquet files, object stores, or remote databases.

   In plain English: The part of a database that actually figures out how to answer your question and fetches the data you asked for.

   Example: "We plugged DuckDB's query engine into our pipeline so analysts can run SQL directly over Parquet files in S3 without loading them into a warehouse."

Related Terms

• Query
• Table
• Query Plan
• Index Scan vs Seq Scan
• Upsert
• Database Trigger
• Left Join
• Query Optimizer
• RDB
• Transform Stream