examples/datafusion-ffi-example/python/tests/_test_physical_optimizer_rule.py

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from __future__ import annotations

import pyarrow as pa
from datafusion import SessionContext
from datafusion_ffi_example import MyPhysicalOptimizerRule


def test_ffi_physical_optimizer_rule_runs_during_planning():
    """A rule added via add_physical_optimizer_rule is invoked while the
    physical plan is built, and the query still returns correct results."""
    rule = MyPhysicalOptimizerRule()
    ctx = SessionContext()
    ctx.add_physical_optimizer_rule(rule)
    batch = pa.RecordBatch.from_arrays(
        [pa.array([1, 2, 3])],
        names=["a"],
    )
    ctx.register_record_batches("t", [[batch]])

    before = rule.optimize_calls()
    result = ctx.sql("SELECT a FROM t").collect()
    after = rule.optimize_calls()

    assert after > before, (
        f"Expected user FFI physical optimizer rule to fire, "
        f"before={before} after={after}"
    )
    assert result[0].column(0).to_pylist() == [1, 2, 3]