Manifest files now optimized during compaction

R2 Data Catalog, a managed Apache Iceberg catalog built into R2, now automatically optimizes manifest files as part of compaction.

Manifest files track the data files that make up an Iceberg table. As a table accumulates many small or fragmented manifests, query engines must read more metadata during query planning, which slows down queries even before any data is scanned.

When compaction runs, R2 Data Catalog now rewrites and clusters manifest files by partition as a best-effort pre-step. This consolidates fragmented manifests, reduces the number of manifests a query engine must open, and lowers metadata I/O overhead. Tables that are already well-clustered are skipped, so the operation only runs when it provides a benefit.

This happens automatically for tables with compaction enabled — no configuration changes are required.

For more information, refer to Table maintenance.