Accelerating String-Heavy Queries with LLM Token Tables

Strings are the most common data type in modern database systems, yet they are often treated as an afterthought in high-performance data formats. While numerical data benefits from specialized, lightweight compression schemes, text is typically handled by general-purpose algorithms such as Zstd, LZ4, or Snappy, which require full-block decompression before processing. In this paper, we explore the potential of repurposing Large Language Model (LLM) tokenizers as a lightweight string compression scheme for databases, similar to FSST, but with a global token table shared across all tables and columns. Operators such as joins and aggregations can exploit this consistent encoding to defer decompression and process encoded values directly. We implement a global token table based on GPT-4's tokenizer in Umbra and demonstrate execution time improvements of up to 2× on string-heavy workloads, while reducing storage and memory consumption by up to 1.65×. Tokenizers integrate well with other compression algorithms, such as FSST, OnPair, or Zstd, while maintaining good compression ratios and high decompression throughput exceeding 6 GB/s on a single CPU core.