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Data & Analytics · Advanced

Delta Transaction Log

The _delta_log folder of ordered JSON commit files and Parquet checkpoints that records every change to a Delta table and provides ACID guarantees.

Definition

Readers reconstruct the table version from the log. Optimistic concurrency resolves concurrent writers. Checkpoints are written every 10 commits by default to speed state reconstruction.

Exam tip

Delta's ACID guarantees come from the transaction log, not from the Parquet files.

Related terms