Policy-Conditioned Constrained Decoding for Column-Level Access Control in Text-to-SQL

Miyamoto Ryoto, Xin Fan, Hayato Yamana


Abstract
Text-to-SQL is increasingly deployed across trust boundaries between data providers and users. Such deployment must balance three competing requirements: policy compliance, answer coverage, and bounded cost. Existing approaches typically decide refusal based on which columns a query mentions and enforce it stochastically. Whether a query is compliant, however, depends not only on which columns appear but on how they are used, and stochastic enforcement cannot deterministically rule out violations. We formalize this requirement as a column-use policy over semantic use: output, filter condition, and aggregation argument. We integrate the policy by aligning each role with grammar productions tracked by the decoder. The resulting system, PCC-SQL, applies a per-token logits mask that deterministically eliminates single-query column-use violations on the supported SQL fragment in a single decoding pass. Across three benchmarks and three open-source models, PCC-SQL achieves 0% Leakage Rate and Coverage up to 88.7% on Spider-CU, while staying within +10% tokens of direct prompting. We additionally assess semantic alignment with execution accuracy.
Anthology ID:
2026.aacl-long.239
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
5377–5391
Language:
URL:
https://aclanthology.org/2026.aacl-long.239/
DOI:
Bibkey:
Cite (ACL):
Miyamoto Ryoto, Xin Fan, and Hayato Yamana. 2026. Policy-Conditioned Constrained Decoding for Column-Level Access Control in Text-to-SQL. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 5377–5391, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Policy-Conditioned Constrained Decoding for Column-Level Access Control in Text-to-SQL (Ryoto et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.239.pdf