Episode #607

Memory Mapped Files

Series: Billion Row Challenge

78 minutes
Published on March 27, 2026

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In this episode we refactor the current solution to use memory mapped files instead of chunked reading with a FileHandle. This requires us to do a bit of pointer wrangling, but in the end we get it back to a working state albeit with just a few small bugs.

Links

Note there are some notable mistakes in this episode (especially with the hashing bits at the end), which we will correct in the next episode. It is valuable to leave in as a topic for explanation in the next episode!

This episode uses Swift 6.2, Xcode 26.2.