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DuckDB speeds string aggregations by grouping on narrow integer keys

duckdb.org by DuckDB Team 14 min read Editor score 7/10

The technique replaces repeated long strings with sorted integer keys for aggregation, then joins the strings back afterward. It is a practical query-design pattern for reducing work on variable-length values.

What

DuckDB's dimension-table technique speeds aggregations over long, repeated strings by grouping on narrow integer keys.

How

A dimension table maps strings to integers; the query aggregates on those keys and joins the strings back at the end.

Why it matters

This can reduce repeated string hashing, copying and comparison in string-heavy analytical queries.

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