{% block title %}lake-sift{% endblock %}

Modes

Value diff: Added, removed, and changed rows & cells. Needs a key.
Schema only: Compare schemas only — no key, reads no data. A pre-run contract gate.
Preview: Estimate the blast radius from Iceberg metadata alone — reads no data.

Source syntax

path/to/*.parquet

A Parquet file or glob.

iceberg:<catalog>/<ns>.<table>[@<snap|ref>[^]]

@1042 a snapshot · @main a branch/tag · @^ that snapshot's parent.

delta:<path>[@<version>]

A Delta table, with optional time-travel version.

sql:<file.sql>

Predicted output schema (schema-only; provide the query's upstreams).

Status

identicalNo difference at all. differencesRows or cells changed. schema changeColumns added, removed, or retyped. runningThe diff is still in flight. errorThe comparison could not run.

Where runs are stored

A SQLite file — default ~/.lake-sift/history.db (override with lake-sift web --db <path>). Only the diff result is saved, with the row/cell listing capped; your Parquet, Iceberg, and Delta data is never copied.

From the CLI

lake-sift <left> <right> --key <id> runs the exact same engine. Docs on GitHub →