Help Center/ Data Lake Insight/ Delta SQL Syntax Reference/ Delta Cleansing and Optimization
Updated on 2025-01-09 GMT+08:00
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Delta Cleansing and Optimization

Cleansing a Delta Table

You can run the VACUUM command on a Delta table to remove data files that are no longer referenced and were created before the retention threshold.

VACUUM delta_table0;
VACUUM delta_table0 RETAIN 168 HOURS;--The unit can only be HOURS.

Optimizing a Delta Table

To improve query speed, Delta Lake supports optimizing the data layout in storage, which will compress many smaller files into larger ones.

optimize delta_table0;
optimize delta_table0 where date >= '2020-01-01';

Z-Ordering

Z-ordering is another technique to speed up queries. Sorting data with Z-order can reorganize the data in storage. When your data is appropriately sorted, you can skip more files and read less data, thus running faster. To sort Z-Order data, specify the columns to sort by in ZORDER BY.

OPTIMIZE delta_table0 ZORDER BY (price);