fix(gfql): explain engine-mismatched index scans - #1838
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lmeyerov
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July 30, 2026 23:28
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What
Add an
gfql_explaindiagnostic when a valid resident adjacency index belongs to the other requested engine and GFQL intentionally declines it for a scan.Why
The mismatch was silent in both pandas-to-polars and polars-to-pandas directions while
show_indexes()remained valid, hiding a severe default-path cliff.Scope
Diagnostic only: no execution, coercion, rebuild, or index-policy change.
Validation
Targeted diagnostic tests, the GFQL index module suite, lint/hygiene, and mypy 2.3.0 passed on DGX.