Delta Table and Delta Data

Delta Lake Notes

Delta Data

• Format for building reliable data lakes
• Provides ACID transactions for big data workloads
• Built on top of Parquet file format
• Adds transaction log layer for consistency
• Enables time travel and rollbacks
• Handles schema evolution
• Optimizes data layout and compaction

Key Features

• Versioning and time travel
• ACID transactions
• Audit history
• Schema enforcement and evolution
• Batch and streaming support
• Table optimization
• Data validation
• Merge operations

Delta Table Components

• Parquet Data Files
  • Store actual table data
  • Column-oriented storage format
  • Compressed and encoded data
• Transaction Log (_delta_log)
  • JSON files tracking changes
  • Contains table metadata
  • Records all transactions
  • Enables isolation and consistency

Common Operations

• Read data: SELECT queries
• Write data: INSERT, DELETE, UPDATE, MERGE
• Optimize: VACUUM, COMPACT
• History tracking: DESCRIBE HISTORY
• Roll back: RESTORE TABLE to version
• Schema updates: ALTER TABLE

Benefits

• Data reliability
• Better query performance
• Built-in data versioning
• Simple integration
• Stream and batch unification
• Scalable metadata handling