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Monitor PREDICT T-SQL statements with extended events in SQL Server Machine Learning Services

  • Artikkeli

Applies to: SQL Server 2017 (14.x) and later Azure SQL Managed Instance

Learn how to use extended events to monitor and troubleshooting PREDICT T-SQL statements in SQL Server Machine Learning Services.

Table of extended events

The following extended events are available in all versions of SQL Server that support the PREDICT T-SQL statement.

name object_type description
predict_function_completed event Builtin execution time breakdown
predict_model_cache_hit event Occurs when a model is retrieved from the PREDICT function model cache. Use this event along with other predict_model_cache_* events to troubleshoot issues caused by the PREDICT function model cache.
predict_model_cache_insert event Occurs when a model is insert into the PREDICT function model cache. Use this event along with other predict_model_cache_* events to troubleshoot issues caused by the PREDICT function model cache.
predict_model_cache_miss event Occurs when a model is not found in the PREDICT function model cache. Frequent occurrences of this event could indicate that SQL Server needs more memory. Use this event along with other predict_model_cache_* events to troubleshoot issues caused by the PREDICT function model cache.
predict_model_cache_remove event Occurs when a model is removed from model cache for PREDICT function. Use this event along with other predict_model_cache_* events to troubleshoot issues caused by the PREDICT function model cache.

To view a list of all columns returned for these events, run the following query in SQL Server Management Studio:

SELECT *
FROM sys.dm_xe_object_columns
WHERE object_name LIKE 'predict%'

Examples

To capture information about performance of a scoring session using PREDICT:

  1. Create a new extended event session, using Management Studio or another supported tool.
  2. Add the events predict_function_completed and predict_model_cache_hit to the session.
  3. Start the extended event session.
  4. Run the query that uses PREDICT.

In the results, review these columns:

  • The value for predict_function_completed shows how much time the query spent on loading the model and scoring.
  • The boolean value for predict_model_cache_hit indicates whether the query used a cached model or not.

Native scoring model cache

In addition to the events specific to PREDICT, you can use the following queries to get more information about the cached model and cache usage:

View the native scoring model cache:

SELECT *
FROM sys.dm_os_memory_clerks
WHERE type = 'CACHESTORE_NATIVESCORING';

View the objects in the model cache:

SELECT *
FROM sys.dm_os_memory_objects
WHERE TYPE = 'MEMOBJ_NATIVESCORING';

Next steps

For more information about extended events (sometimes called XEvents), and how to track events in a session, see these articles: