DBCC PDW_SHOWEXECUTIONPLAN (Transact-SQL)
Displays the SQL Server execution plan for a query running on a specific SQL Data Warehouse or Parallel Data Warehouse Compute node or Control node. Use this to troubleshoot query performance problems while queries are running on the Compute nodes and Control node.
Once query performance problems are understood for SMP SQL Server queries running on the Compute nodes, there are several ways to improve performance. Possible ways to improve query performance on the Compute nodes include creating multi-column statistics, creating non-clustered indexes, or using query hints.
Syntax for Azure SQL Data Warehouse:
DBCC PDW_SHOWEXECUTIONPLAN ( distribution_id, spid ) [;]
Syntax Azure Parallel Data Warehouse:
DBCC PDW_SHOWEXECUTIONPLAN ( pdw_node_id, spid ) [;]
Identifier for the distribution that is running the query plan. This is an integer and cannot be NULL. Used when targeting SQL Data Warehouse.
Identifier for the node that is running the query plan. This is an integer and cannot be NULL. Used when targeting an Appliance.
Identifier for the SQL Server session that is running the query plan. This is an integer and cannot be NULL.
Requires CONTROL permission on SQL Data Warehouse.
Requires VIEW-SERVER-STATE permission on the Appliance.
Examples: SQL Data Warehouse
A. DBCC PDW_SHOWEXECUTIONPLAN Basic Syntax
When running on a SQL Data Warehouse instance, modify the above query to also select the distribution_id.
SELECT [sql_spid], [pdw_node_id], [request_id], [dms_step_index], [type], [start_time], [end_time], [status], [distribution_id] FROM sys.dm_pdw_dms_workers WHERE [status] <> 'StepComplete' and [status] <> 'StepError' order by request_id, [dms_step_index];
This will return the spid for each actively running distribution. If you were curious as to what distribution 1 was running in session 375, you would run the following command.
DBCC PDW_SHOWEXECUTIONPLAN ( 1, 375 );
Examples: Parallel Data Warehouse
B. DBCC PDW_SHOWEXECUTIONPLAN Basic Syntax
The query that is running too long is either running a DMS query plan operation or a SQL query plan operation.
If the query is running a DMS query plan operation, you can use the following query to retrieve a list of the node IDs and session IDs for steps that are not complete.
SELECT [sql_spid], [pdw_node_id], [request_id], [dms_step_index], [type], [start_time], [end_time], [status] FROM sys.dm_pdw_dms_workers WHERE [status] <> 'StepComplete' and [status] <> 'StepError' AND pdw_node_id = 201001 order by request_id, [dms_step_index], [distribution_id];
Based on the results of the preceding query, use the sql_spid and pdw_node_id as parameters to DBCC PDW_SHOWEXECUTIONPLAN. For example, the following command shows the execution plan for pdw_node_id 201001 and sql_spid 375.
DBCC PDW_SHOWEXECUTIONPLAN ( 201001, 375 );