omnigraph/docs/user/operations/maintenance.md

Maintenance: Optimize, Repair & Cleanup

Addressing. optimize, repair, and cleanup are storage-plane CLI commands: they run with direct storage access against a positional URI, --target, or --cluster <dir|s3://…> --cluster-graph <id> (which resolves the graph's storage URI from the served cluster state, so you needn't know the <storage>/graphs/<id>.omni layout). They never run through a server, and reject --server / --graph or a --target that resolves to a remote (http(s)://) URL with a declared error. There are no server routes for them by design — to maintain a server-backed graph, run them out-of-band against the graph's storage URI. See the Command planes section of cli-reference.md.

optimize — non-destructive

• Compacts every node + edge table on main, then publishes the compacted version to the __manifest so the manifest's recorded version tracks the compacted state. Reads pin the manifest version, so without this publish compaction would be invisible to readers and would break the version precondition of the next schema apply / strict update/delete ("stale view … refresh and retry"). The publish advances the graph version (a system-attributed commit) only for tables that actually compacted.
• Rewrites small fragments into fewer large ones; old fragments remain reachable via older versions until cleanup runs.
• Each table's compact→publish serializes with concurrent mutations on the same table. A crash mid-operation is recovered automatically on the next open (compaction is content-preserving, so roll-forward is always safe).
• Requires a recovered graph. optimize refuses (errors) when a pending crash-recovery operation is present — operating on an unrecovered graph could publish a partial write that recovery would roll back. Reopen the graph to run recovery, then re-run optimize.
• Uncovered drift is skipped, not interpreted. If a table's underlying version is ahead of the version recorded in __manifest and no crash-recovery record covers that movement, optimize reports skipped: DriftNeedsRepair with the manifest/head versions and leaves the table untouched. Run omnigraph repair to classify and explicitly publish that drift.
• Bounded by OMNIGRAPH_MAINTENANCE_CONCURRENCY (default 8).
• Returns per-table stats: table_key, fragments_removed, fragments_added, committed, skipped, manifest_version, lance_head_version.
• Blob tables are skipped. A table that declares any Blob property is not compacted: it is reported with skipped: BlobColumnsUnsupportedByLance (and logged) instead of compacted, and the rest of the sweep proceeds normally. Reads and writes are unaffected — only compaction is. Consequence: fragment count and deleted-row space on blob tables are not reclaimed; query results are never affected.

repair — explicit

• Handles uncovered manifest/head drift: a table's underlying version is ahead of the manifest pin and no crash-recovery record explains the movement.
• Preview by default. omnigraph repair --json <uri> reports each table's classification, action, manifest/head versions, underlying operation names, and any classification error. --confirm publishes only verified maintenance drift; if any suspicious or unverifiable table is refused, the CLI prints the per-table output and exits non-zero. --force --confirm also publishes suspicious or unverifiable drift after operator review.
• Classifies drift by reading the table's transaction history from manifest_version + 1 through the current head. Only fragment-reservation and rewrite (compaction) operations are verified maintenance. Semantic operations such as append, delete, update, merge, or missing transaction history are not auto-healed.
• Publishes repair by advancing __manifest to the existing head; it does not rewrite data. If the publish succeeds, normal reads and strict writes use the repaired version. If it fails, no new data-side partial state was created.
• Requires a clean recovery state. A pending crash-recovery operation still belongs to automatic recovery, not manual repair.

cleanup — destructive

• Garbage-collects old versions per table.
• Removes versions (and their unique fragments) older than the retention policy.
• Policy options keep_versions and older_than — at least one is required.
• Returns per-table stats: table_key, bytes_removed, old_versions_removed, error.
• Fault-isolated per table. A single table's transient failure (version GC or orphan reclaim) is recorded on that table's stats row (with an error) and logged, and never aborts the healthy tables — cleanup is the convergence backstop, so it does as much as it can and converges on re-run. The CLI reports any failed tables; rerun cleanup to retry them.
• CLI guards with --confirm; without it, prints a preview line.
• Recovery floor: --keep < 3 may garbage-collect versions that crash recovery needs as a rollback target. Default --keep 10 is safe.
• Orphaned-branch reconciliation: before the version GC, cleanup reclaims any per-table or commit-graph branch absent from the manifest branch list. These orphans arise when a branch_delete flips the manifest authority but a downstream best-effort reclaim does not complete (see branches-commits.md). The reconciler is idempotent (it no-ops once nothing is orphaned), runs regardless of the keep_versions / older_than values (those gate version GC only), and never reclaims main or system-branch forks. Reclaimed forks are logged.

Tombstones

Logical sub-table delete markers in __manifest that exclude a sub-table version from snapshot reconstruction.

Internal schema migrations

Version evolutions of the on-disk __manifest shape are reconciled automatically on the first write under a new binary. An on-disk stamp records the shape; the binary migrates it forward before reading state, and reads are side-effect-free. No operator action is required for in-place upgrades. See storage.md → Internal schema versioning for the full mechanism.

A binary opening a manifest stamped at a version higher than it knows about refuses to publish with a clear "upgrade omnigraph first" error — old binaries cannot clobber a newer schema.