Function ensure_begin_non_decreasing 

pub fn ensure_begin_non_decreasing(
    stream_id: &str,
    batch: &RecordBatch,
) -> Result<(), Error>

Verifies that batch’s begin column is non-decreasing, naming stream_id and the offending row/values in both the returned error and (unlike a plain anyhow::ensure!) an error! log line emitted immediately before it: nothing on ensure_begin_non_decreasing‘s callers’ error propagation path (MaterializedView::scan -> DataFusion planning -> the flight SQL service) logs a planning-time error at error level, so the check logs itself instead of relying on that propagation.

pub, not inlined into write_partition, so rust/analytics/tests/ (an external integration crate that can only reach pub items) can call it directly with a hand-built batch.