DeltaSyncCapable mixin - adapter_capabilities library

The remote adapter can serve incremental pulls: instead of returning the full dataset every cycle, it returns only entities modified at or after a watermark (typically WHERE modified_at >= ? on the backend).

When a remote adapter mixes this in (and DatumConfig.enableDeltaSync is true, its default), the sync engine's pull phase calls readSince with the last sync watermark minus DatumConfig.deltaSyncOverlap (clock-skew tolerance; re-delivered rows are skipped by the strictly-newer check, so the overlap is idempotent). The engine still falls back to a full readAll for the first sync of a user and for cycles that need the complete remote id set (detectRemoteDeletions).

Soft deletions (isDeleted flips bump modifiedAt) propagate through deltas naturally. Hard remote deletions are invisible to an incremental pull — keep using soft deletes, or enable detectRemoteDeletions for full-scan cycles.

Which column to compare: prefer a server-maintained received-at timestamp (set by the backend on every write, e.g. a server_updated_at trigger column) over the entity's client-set modifiedAt. A device that reconnects after a week pushes rows whose modifiedAt is a week old — older than every other device's watermark — so a modifiedAt comparison would silently miss them, while a server received-at is always newer than any previously issued watermark.

DeltaSyncCapable<T extends DatumEntityInterface> mixin

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Operators

adapter_capabilities library