Closing the Cross-Dialect Gap: Query Plans as a Portable Interface in Text-to-SQL

Corentin Royer, Robin Oester, Yotam Perlitz, Yannick Metz, Andrea Giovannini, Mennatallah El-Assady


Abstract
Text-to-SQL systems are typically trained and evaluated on a single dialect (SQLite), yet production deployments span PostgreSQL, MySQL, ClickHouse, and beyond. We show that this single-dialect assumption leads to a substantial drop in lower-bound dialect accuracy for every model we tested. The drop persists across scale, architecture, and even purpose-built text-to-SQL systems. We argue that the fix is to change the generation target: instead of asking an LLM to emit dialect-specific SQL, we have it emit a dialect-agnostic relational algebra query plan, which a deterministic compiler then renders into SQL for any supported backend. Across thirteen models from 3B to frontier scale, this restores cross-dialect portability nearly uniformly, at a small cost in peak accuracy on the model’s home dialect for capable prompted models and none once fine-tuned on plans; under matched fine-tuning, plan supervision yields a stronger model than SQL supervision. We also introduce DF-Match, a question-aware result-set comparator needed to evaluate fairly across dialects, where existing metrics confound semantic errors with benign cross-dialect variation. More broadly, the result is a reminder that a generation target chosen for execution is not necessarily the one that maximizes generation quality.
Anthology ID:
2026.findings-emnlp.2422
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
52002–52021
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2422/
DOI:
Bibkey:
Cite (ACL):
Corentin Royer, Robin Oester, Yotam Perlitz, Yannick Metz, Andrea Giovannini, and Mennatallah El-Assady. 2026. Closing the Cross-Dialect Gap: Query Plans as a Portable Interface in Text-to-SQL. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 52002–52021, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Closing the Cross-Dialect Gap: Query Plans as a Portable Interface in Text-to-SQL (Royer et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2422.pdf