Encoding Types

Concepts covered: paCompression

What They Want to Hear 'Parquet applies encoding per column before compression. Dictionary encoding maps repeated values to small integers, so a column of 1 million country codes becomes 1 million tiny integers plus a 200-entry dictionary. RLE (run-length encoding) stores repeated consecutive values as (value, count). Delta encoding stores differences between sequential values, perfect for timestamps.' The key insight: encoding converts data into a more compressible form BEFORE the compression algorithm runs.

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