Change Data Feed in Delta
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This document discusses Delta Change Data Feed (CDF), which allows capturing changes made to Delta tables. It describes how CDF works by storing change events like inserts, updates and deletes. It also outlines how CDF can be used to improve ETL pipelines, unify batch and streaming workflows, and meet regulatory needs. The document provides examples of enabling CDF, querying change data and storing the change events. It concludes by offering a demo of CDF in Jupyter notebooks.
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Change Data Feed in Delta
- 1. Delta Change Data Feed Joseph Torres Rahul Mahadev Itai Weiss
- 2. Agenda ▪ Data capture challenges ▪ Change Data Feed on the Lakehouse ▪ Capture Changes ▪ Process Changes ▪ Demo
- 3. Who are we? - Jose Torres ● Software Engineer - Databricks ● Committer - Delta Lake, Apache Spark ● Database and cooking enthusiast
- 4. Who are we? - Rahul Mahadev ● Software Engineer– Databricks ● Delta Lake Committer ● MS Computer Science, University of Illinois Urbana-Champaign
- 5. Who are we? - Itai Weiss • Lead Solution Architect– Databricks • Working with Apache Spark! since v1.6 • Consulted for numerous firms across Financial, Insurance, Tech, Pharma, Manufacturing, Retail and Transportation
- 6. Delta Lake An open, reliable, performant, and secure data storage and management layer for your data ■ Fresh & reliable data with a single source of truth ■ Data warehouse performance with data lake economics ■ Advanced security and standards to meet compliance needs ■ Open format
- 7. Current Challenges Delta table v-1 Spark Insert Spark Updates Delta table v Spark Delete Spark Union ■ Big data increases the complexity of • Lots of data • Changes infrequently • Just want to process the newest changes Full Outer Join Inserts Updates Deletes
- 8. ■ Read only the changed data ■ Avoid full table scans ■ Reduce compute and memory Solve data challenges with CDF Improve ETL pipelines Unify batch and streaming BI on your data lake Meet regulatory needs For All your use cases Delta table with CDF Spark Union Delta Change Data Feed
- 9. Where Delta Change Data Feed Applies Raw Ingestion and History BRONZE Filtered, Cleaned, Augmented SILVER Business-level Aggregates GOLD CD F External feeds, Other CDC output, Extracts
- 10. How Does Delta Change Data Feed Work? PK B A1 B1 A2 B2 A3 B3 Original Table (v1) PK B A2 Z2 A3 B3 A4 B4 Change data (Merged as v2) PK B Change Type Time Versio n A2 B2 Preimage 12:00:0 0 2 A2 Z2 Postimage 12:00:0 0 2 A3 B3 Delete 12:00:0 0 2 A4 B4 Insert 12:00:0 0 2 Change Data Feed Output A1 record did not receive an update or delete. So it will not be output by CDF.
- 11. Consuming the Delta Change Data Feed Stream-based Consumption ● Delta Change Feed is processed as each source commit completes ● Rapid source commits can result in multiple Delta versions being included in a single micro-batch Batch Consumption ● Batches are constructed based in time-bound windows which may contain multiple Delta versions A2 B2 Preimage 12:00:00 2 A2 Z2 Postimage 12:00:00 2 A3 B3 Delete 12:00:00 2 A4 B4 Insert 12:00:00 2 A5 B5 Insert 12:08:0 0 3 A6 B6 Insert 12:09:00 4 A6 B6 Preimage 12:10:05 5 A6 Z6 Postimage 12:10:05 5 A5 B5 Insert 12:08:00 3 A6 B6 Insert 12:09:00 4 12:00 A6 B6 Preimage 12:10:05 5 A6 Z6 Postimag e 12:10:05 5 12:10:00 12:20 12:08 12:10:10 Stream - micro batches Batch - every 10 mins 12:00
- 12. Storing the Delta Change Data Feed Changes to the table are stored as ordered, atomic units called commits Add 1.parquet Add 2.parquet Remove 1.parquet Remove 2.parquet Add 3.parquet 000000.json 000001.json …
- 13. Storing the Delta Change Data Feed ● When Change Data Feed is enabled, commits will reference an additional set of files containing the change data events ● These files contains the updated and deleted records Add 1.parquet Add 2.parquet Remove 1.parquet Remove 2.parquet Add 3.parquet Cdf 1.parquet 000000.json 000001.json …
- 14. Storing the Delta Change Data Feed ● Silver & Gold Tables ○ Improve Delta performance by processing only data changes, and simplify ETL/ELT operations ● Materialized Views ○ Create up-to-date, aggregated views of information based on the data changes ● Transmit Changes ○ Send only the data changes to downstream systems ● Audit Trail Table ○ Capture and store all the data changes over time, including inserts, updates, and deletes
- 15. When to Use Delta Change Data Feed ● Delta changes include updates and/or deletes ● Delta changes are append only ● Small fraction of records updated in each batch ● Most records in the table updated in each batch ● Data received from external sources is in CDC format ● Data received comprises destructive loads ● Send data changes to downstream application ● Find and ingest data outside of the Lakehouse
- 16. Getting started with Delta Change Data Feed spark.conf.set('spark.databri cks.delta.properties.defaults .enableChangeDataFeed', True) ALTER TABLE ... SET TBLPROPERTIES (delta.enableChangeDataFeed = true); Enable CDF on TABLE… … or Establish CDF on CLUSTER in SQL, Python, or Scala in Python, or Scala
- 17. Using Delta Change Data Feed INSERT INTO TABLE ... USING delta ... as SELECT … FROM table_changes(...) SELECT … FROM table_changes('tableName', startingVersion [,endingVersion]) or SELECT … FROM table_changes('tableName', 'startingTimestamp' [,'endingTimestamp']) Query changes… … and store them in SQL, Python, or Scala
- 18. Getting started with Delta Change Data Feed
- 19. Let’s look at some notebooks
- 20. Feedback Your feedback is important to us. Don’t forget to rate and review the sessions.