What is the problem the feature request solves?
Deletion-vector preparation in native/core/src/execution/delta_dv.rs fetches the data file's footer through DFParquetMetadata directly. It fills the shared metadata cache correctly, but it runs before the scan creates its instrumented reader, so the preparation footer and page-index I/O bypass the final scan's scan_io_* counters while the later open reports a cache hit.
Describe the potential solution
A preparation hook in the shared scan builder, or a shared metadata helper with the same metrics owner, so preparation and normal reads share one place for metadata policy and instrumentation. The preparation accounting must land in the final scan's counters; a separate factory whose counters are discarded keeps the gap. Cold-cache and warm-cache tests verify that preparation I/O is counted, the footer is reused, and warm opens avoid storage reads, while keeping the INT96 stamping on cached metadata.
Additional context
Raised in the #5365 review (item 7); filed as a follow-up.
What is the problem the feature request solves?
Deletion-vector preparation in
native/core/src/execution/delta_dv.rsfetches the data file's footer throughDFParquetMetadatadirectly. It fills the shared metadata cache correctly, but it runs before the scan creates its instrumented reader, so the preparation footer and page-index I/O bypass the final scan'sscan_io_*counters while the later open reports a cache hit.Describe the potential solution
A preparation hook in the shared scan builder, or a shared metadata helper with the same metrics owner, so preparation and normal reads share one place for metadata policy and instrumentation. The preparation accounting must land in the final scan's counters; a separate factory whose counters are discarded keeps the gap. Cold-cache and warm-cache tests verify that preparation I/O is counted, the footer is reused, and warm opens avoid storage reads, while keeping the INT96 stamping on cached metadata.
Additional context
Raised in the #5365 review (item 7); filed as a follow-up.