MaxCompute - Supports Freeride and Analyze to Collect Metadata for Optimizers
Feb 08 2021MaxCompute
Target customers: developers and analysts. Features released: The MaxCompute SQL optimizer is a cost-based optimizer. It can accurately estimate the costs based on the metadata of tables. The metadata includes the number of rows and the average length of strings. If the optimizer cannot obtain accurate metadata, the optimizer may miscalculate the costs and generate inappropriate execution plans. Therefore, metadata collection is crucial for the optimizer. MaxCompute now provides two tools to collect the metadata of tables: Analyze for asynchronous collection: If you use Analyze, you must run commands to proactively and asynchronously collect table data. You are charged for table data scans. Freeride for synchronous collection: If you use Freeride, you must configure runtime parameters to enable Freeride and collection plans before you execute the CREATE TABLE...AS... or INSERT statement. Column statistics are automatically collected while data is generated. This method is more automated but may prolong your query. MaxCompute does not collect your sensitive information, such as business information.