Yuhua Jiang, Shuang Cheng, Yihao Liu, Ermo Hua, Che Jiang, Weigao Sun, Yu Cheng, Feifei Gao, Biqing Qi, Bowen Zhou. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers). 2026.

Late Materialization (LM) is a critical technique applied in traditional column stores to speed up analytical queries. However, with modern analytical databases evolved to incorporate a vectorized columnar execution engine, LM's benefits in I/O reduction and fast columnar query processing have diminished. In this paper, we redefine the concept of Late Materialization in the context of modern analytical databases and propose Selective Late Materialization (SLM) to allow each attribute in a query to choose its own materialization point that yields the minimum cost. SLM expands the solution space of the traditional materialization problem from one unified hard-coded binary decision (i.e., early or late) for all attributes to per attribute per query decisions. By integrating SLM into DuckDB, we show that SLM consistently outperforms the baselines of Early Materialization and Late Materialization by 14.7% and 8.9%, respectively, on average using the Join Order Benchmark (JOB), with up to 76.7% latency reduction for individual queries. We observe similar results for the TPC-DS benchmark.

Lightweight data compression is a key technique that allows column stores to exhibit superior performance for analytical queries. Despite a comprehensive study on dictionary-based encodings to approach Shannon's entropy, few prior works have systematically exploited the serial correlation in a column for compression. In this paper, we propose LeCo (i.e., Learned Compression), a framework that uses machine learning to remove the serial redundancy in a value sequence automatically to achieve an outstanding compression ratio and decompression performance. LeCo presents a general approach to this end, making existing algorithms such as Frame-of-Reference (FOR), Delta Encoding, and Run-Length Encoding (RLE) special cases under our framework. Our microbenchmark with three synthetic and eight real-world data sets shows that a prototype of LeCo achieves a Pareto improvement on both compression ratio and random access speed over the existing solutions. When integrating LeCo into widely-used applications, we observe up to 5.2× speed up in a data analytical query in the Arrow columnar execution engine, and a 16% increase in RocksDB's throughput.