PolySQL: Scaling Text-to-SQL Evaluation Across SQL Dialects via Automated Backend Isomorphism

Yotam Perlitz, Elad Venezian, Corentin Royer, Francesco Fusco, Andrea Giovannini


Abstract
SQL dialects vary in syntax, types, and functions across database engines. Text-to-SQL benchmarks, however, predominantly support only SQLite. This creates a critical evaluation gap: cross-dialect evaluation reveals weak per-query agreement (Cohen’s ), showing that SQLite performance is an unreliable proxy for other dialects. Yet such evaluation remains prohibitively difficult: existing approaches either require expensive manual query transpilation or rely on tools that often fail on complex SQL. To close this gap, we introduce PolySQL, a novel dual-execution method that eliminates the need for query transpilation by comparing normalized execution results. Notably, our approach achieves higher evaluation fidelity than query transpilation with 100% query coverage. PolySQL comprises three datasets, enabling the first large-scale cross-dialect study. Our study reveals a 10.1% average accuracy drop from SQLite to other dialects and identifies a significant dialect difficulty hierarchy. We find this degradation stems from logical rather than syntactic errors (61% vs. 8%). We release our framework code and leaderboard to enable rigorous dialect-robust evaluation.

Code, Results and Environments are shared in https://github.com/IBM/polysql
Anthology ID:
2026.emnlp-main.23
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
499–512
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URL:
https://aclanthology.org/2026.emnlp-main.23/
DOI:
Bibkey:
Cite (ACL):
Yotam Perlitz, Elad Venezian, Corentin Royer, Francesco Fusco, and Andrea Giovannini. 2026. PolySQL: Scaling Text-to-SQL Evaluation Across SQL Dialects via Automated Backend Isomorphism. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 499–512, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
PolySQL: Scaling Text-to-SQL Evaluation Across SQL Dialects via Automated Backend Isomorphism (Perlitz et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.23.pdf