writeDeletes
fun writeDeletes(rel: RelationReader, defaultValidFromMicros: Long = systemTimeMicros, defaultValidToMicros: Long = MAX_LONG)
Batch delete: deletes every row in rel (keyed by _iid).
Per-row valid times come from the rel's _valid_from / _valid_to columns when present and non-null; otherwise the defaultValidFromMicros / defaultValidToMicros defaults apply. Rejects zero-width or inverted ranges — one check over the defaults if the rel has no per-row temporal columns; otherwise per-row.