SQLite Storage Components

Depot is split into the conveyer hot path plus workflow compaction. Workflow compaction is the only compaction publish/delete authority.

Conveyer

The conveyer is the request path used by the SQLite VFS.

Responsibilities:

• Resolve bucket/database branch ancestry for reads.
• Commit dirty pages as LTX DELTA chunks under BR/{database_id}/DELTA/{txid}/{chunk}.
• Write PIDX owner rows for dirty pages.
• Write COMMITS/{txid} and VTX/{versionstamp} in the same commit transaction.
• Maintain META/head, quota counters, and access-touch manifest fields.
• Update SQLITE_CMP_DIRTY/{database_branch_id} and send throttled DeltasAvailable workflow wakeups when hot lag crosses compaction thresholds.
• Create buckets, create databases, fork buckets, fork databases, and write branch records/catalog markers.
• Create and resolve restore points. Pinned restore points write FDB pins directly and start as PinStatus::Ready.

Lease ownership: none. Correctness relies on Pegboard single-writer exclusivity for a live database plus FDB transaction fences. The conveyer must not take compactor leases.

Workflow Compaction

The workflow compaction path uses one persistent DB manager plus hot and reclaim companion workflows per database branch.

Responsibilities:

• Coalesce commit wakeups through SQLITE_CMP_DIRTY/{database_branch_id} and DeltasAvailable signals.
• Plan hot jobs from current FDB state instead of trusting signal payloads.
• Carry the branch lifecycle generation through planned jobs and reject stale stage, publish, or reclaim work after branch deletion or recreation.
• Have the hot companion write staged shard blobs under CMP/stage/{job_id}/hot_shard.
• Install matching hot job output by copying staged blobs to reader-visible SHARD, advancing CMP/root, and compare-and-clearing expected PIDX rows.
• Have the reclaimer delete only manager-authorized FDB rows and stale staged output.
• Keep automatic PITR interval coverage and retained restore point pins live until reclaim can prove they are no longer needed.
• Stop the manager and companion workflows through DestroyDatabaseBranch when a database branch is no longer live.

Lease ownership: none. Gasoline workflow uniqueness uses only the database branch id tag.

Ownership Summary

Component	Main writes	Lease
Conveyer	META/head, COMMITS, VTX, PIDX, DELTA, branch records, restore points	None
Workflow DB manager	CMP/root, live SHARD, PITR_INTERVAL, matching PIDX clears	None
Workflow companions	Staged hot output and manager-authorized FDB cleanup	None

The components share branch metadata and pin counters, but each mutable manifest field has one owner.