windmill/backend/windmill-duckdb-ffi-internal/README_DEV.md

This crate is compiled separately from the backend workspace because the bundled DuckDB's libc++ clashes with deno_core's when both live in one process.

The symptom was opaque errors. DuckDB errors worked, except when attached to a DuckLake with the deno_core feature on:

ATTACH 'ducklake' AS dl; USE dl;
CREATE TABLE IF NOT EXISTS t (x string not null);
INSERT INTO t VALUES (NULL);

gave Unknown exception in ExecutorTask::Execute instead of Constraint Error: NOT NULL constraint failed: t.x. The opaque error comes from the C++ DuckDB library: https://github.com/duckdb/duckdb/blob/f99fed1e0b16a842573f9dad529f6c170a004f6e/src/parallel/executor_task.cpp#L58

The worker never links this crate: it runs windmill_duckdb_runner (src/bin) as a separate process for every job. See docs/duckdb-execution.md.