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Enhance readme with DeltaLake optimization steps #2902

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22 changes: 19 additions & 3 deletions ...-source-data-platforms/oci-data-flow/code-examples/DeltaLake_Optimize/readme.md
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Expand Up @@ -17,41 +17,57 @@ OCI Data Flow supports Delta Lake by default when your Applications run Spark 3.
How to optimize data lake using DeltaLake functions:
Configure your preferences (please check DeltaLake doc):

```
spark.conf.set('spark.databricks.delta.retentionDurationCheck.enabled', 'False')
spark.conf.set('spark.databricks.delta.optimize.repartition.enabled','True')
spark.conf.set('spark.databricks.delta.optimize.preserveInsertionOrder', 'False')

Preserve vacuum history:
#Preserve vacuum history:
spark.conf.set('spark.databricks.delta.vacuum.logging.enabled','True')

Set retention time for optimized files (ready to delete:
#Set retention time for optimized files (ready to delete:
spark.conf.set("spark.databricks.delta.deletedFileRetentionDuration","0")
```


Check existing table details (look for numFiles and sizeInBytes:
```
spark.sql("describe detail atm").show(truncate=False)
```
```
+------+------------------------------------+--------------------------------+-----------+----------------------------------------------------+-----------------------+-------------------+------------------+--------+-----------+----------+----------------+----------------+------------------------+
|format|id |name |description|location |createdAt |lastModified |partitionColumns |numFiles|sizeInBytes|properties|minReaderVersion|minWriterVersion|tableFeatures |
+------+------------------------------------+--------------------------------+-----------+----------------------------------------------------+-----------------------+-------------------+------------------+--------+-----------+----------+----------------+----------------+------------------------+
|delta |c15ad4ca-8c0f-4747-b064-1492d7b4b3c4|spark_catalog.default.hsl_trains|NULL |oci://dataflow_app@fro8fl9kuqli/hsl_trains_data_part|2024-09-05 10:19:10.057|2024-09-06 08:45:01|[year, month, day]|2024 |16333676 |{} |1 |2 |[appendOnly, invariants]|
+------+------------------------------------+--------------------------------+-----------+----------------------------------------------------+-----------------------+-------------------+------------------+--------+-----------+----------+----------------+----------------+------------------------+
```

Run optimzation:
```
spark.sql("OPTIMIZE atm").show(truncate=False)
```

Check files you can delete:
```
spark.sql("vacuum atm RETAIN 0 HOURS DRY RUN")
```

Delete optimized and consolidated files:
```
spark.sql("vacuum atm RETAIN 0 HOURS")
```

and check details of your table:
```
spark.sql("describe detail atm").show(truncate=False)
```
```
+----------------+----------------+------------------------+
|format|id |name |description|location |createdAt |lastModified |partitionColumns |numFiles|sizeInBytes|properties|minReaderVersion|minWriterVersion|tableFeatures |
+------+------------------------------------+--------------------------------+-----------+----------------------------------------------------+-----------------------+-------------------+------------------+--------+-----------+----------+----------------+----------------+------------------------+
|delta |c15ad4ca-8c0f-4747-b064-1492d7b4b3c4|spark_catalog.default.hsl_trains|NULL |oci://dataflow_app@fro8fl9kuqli/hsl_trains_data_part|2024-09-05 10:19:10.057|2024-09-06 08:47:48|[year, month, day]|7 |1583521 |{} |1 |2 |[appendOnly, invariants]|
+------+------------------------------------+--------------------------------+-----------+----------------------------------------------------+-----------------------+-------------------+------------------+--------+-----------+----------+----------------+----------------+------------------------+
+------+------------------------------------+--------------------------------+-----------+----------------------------------------------------+-----------------------+-------------------+------------------+--------+-----------+----------+----------------+----------------+------------------------+
```

Enjoy increased performance of your queries!

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