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CREATE WORKLOAD CLASSIFIER (Transact-SQL)

  • Artikkeli

Applies to: Azure Synapse Analytics

Creates a classifier object for use in workload management. The classifier assigns incoming requests to a workload group based on the parameters specified in the classifier statement definition. Classifiers are evaluated with every request submitted. If a request isn't matched to a classifier, it's assigned to the default workload group. The default workload group is the smallrc resource class.

Note

Classifying managed identities (MI) behavior differs between the dedicated SQL pool in Azure Synapse workspaces and the standalone dedicated SQL pool (formerly SQL DW). While the standalone dedicated SQL pool MI maintains the assigned identity, Azure Synapse workspaces adds MI to the dbo role. This can't be changed. The dbo role, by default, is classified to smallrc. Creating a classifier for the dbo role allows for assigning requests to a workload group other than smallrc. If dbo alone is too generic for classification and has broader impacts, consider using label, session or time-based classification in conjunction with the dbo role classification.

Transact-SQL syntax conventions

Syntax

CREATE WORKLOAD CLASSIFIER classifier_name
WITH
    ( WORKLOAD_GROUP = 'name'
    , MEMBERNAME = 'security_account'
    [ [ , ] WLM_LABEL = 'label' ]
    [ [ , ] WLM_CONTEXT = 'context' ]
    [ [ , ] START_TIME = 'HH:MM' ]
    [ [ , ] END_TIME = 'HH:MM' ]
    [ [ , ] IMPORTANCE = { LOW | BELOW_NORMAL | NORMAL | ABOVE_NORMAL | HIGH } ] )
[ ; ]

Note

This syntax is not supported by serverless SQL pool in Azure Synapse Analytics.

Arguments

classifier_name

Specifies the name by which the workload classifier is identified. classifier_name is sysname. This parameter can be up to 128 characters long, and must be unique within the instance.

WORKLOAD_GROUP = 'name'

When the conditions are met by the classifier rules, name maps the request to a workload group. name is sysname. This parameter can be up to 128 characters long, and must be a valid workload group name at the time of classifier creation.

Available workload groups can be found in sys.workload_management_workload_groups catalog view.

MEMBERNAME = 'security_account'

The security account used to classify against. security_account is sysname, with no default. security_account can be a database user, database role, Microsoft Entra login, or Microsoft Entra group.

Note

Use the user_name() function, when connected to the system, to verify the MEMBERNAME that the classification process will use to classify the request. Verifying the MEMBERNAME with the user_name() function can be helpful troubleshooting Microsoft Entra ID or service principal classification issues. If user_name() returns dbo, you can use dbo as the MEMBERNAME to classify the requests. All members of the dbo role will be classified. Additional classification parameters such as WLM_LABEL or WLM_CONTEXT can also be used to specifically classify requests from multiple Microsoft Entra accounts mapping to the dbo role.

WLM_LABEL

Specifies the label value that a request can be classified against. Label is an optional parameter of type nvarchar(255). Use the OPTION (LABEL) in the request to match the classifier configuration.

For example:

CREATE WORKLOAD CLASSIFIER wcELTLoads
WITH (
    WORKLOAD_GROUP = 'wgDataLoad',
    MEMBERNAME = 'ELTRole',
    WLM_LABEL = 'dimension_loads'
);
    
SELECT COUNT(*) FROM DimCustomer
OPTION (LABEL = 'dimension_loads');

WLM_CONTEXT

Specifies the session context value that a request can be classified against. WLM_CONTEXT is an optional parameter of type nvarchar(255). Use the sys.sp_set_session_context with the variable name equal to wlm_context before submitting a request to set the session context.

For example:

CREATE WORKLOAD CLASSIFIER wcDataLoad
WITH (
    WORKLOAD_GROUP = 'wgDataLoad',
    MEMBERNAME = 'ELTRole',
    WLM_CONTEXT = 'dim_load'
);

--set session context
EXEC sys.sp_set_session_context @key = 'wlm_context', @value = 'dim_load';

--run multiple statements using the wlm_context setting
SELECT COUNT(*) FROM stg.daily_customer_load;
SELECT COUNT(*) FROM stg.daily_sales_load;

--turn off the wlm_context session setting
EXEC sys.sp_set_session_context @key = 'wlm_context', @value = NULL;

START_TIME and END_TIME

Specifies the start time and end time that a request can be classified against. Both START_TIME and END_TIME are of the HH:mm format in the UTC time zone. START_TIME and END_TIME must be specified together.

For example:

CREATE WORKLOAD CLASSIFIER wcELTLoads
WITH (
    WORKLOAD_GROUP = 'wgDataLoads',
    MEMBERNAME = 'ELTRole',
    START_TIME = '22:00',
    END_TIME = '02:00'
);

IMPORTANCE = { LOW | BELOW_NORMAL | NORMAL | ABOVE_NORMAL | HIGH }

Specifies the relative importance of a request. IMPORTANCE is one of the following options:

  • LOW
  • BELOW_NORMAL
  • NORMAL (default)
  • ABOVE_NORMAL
  • HIGH

If IMPORTANCE isn't specified, the importance setting of the workload group is used. The default workload group importance is NORMAL. Importance influences the order which requests are scheduled, thus giving first access to resources and locks.

Remarks

The maximum number of user-defined classifiers is 100. Additional configurations beyond this limit aren't supported. We recommend that you group classifiers under a common category for efficient application of a single setting, across multiple workloads or users.

Classification parameter weighting

A request can match against multiple classifiers. There's a weighting for the classifier parameters. The higher weighted matching classifier is used to assign a workload group and importance. The weighting goes as follows:

Classifier parameter Weight
USER 64
ROLE 32
WLM_LABEL 16
WLM_CONTEXT 8
START_TIME/END_TIME 4

Consider the following classifier configurations.

CREATE WORKLOAD CLASSIFIER classifierA
WITH (
    WORKLOAD_GROUP = 'wgDashboards',
    MEMBERNAME = 'userloginA',
    IMPORTANCE = HIGH,
    WLM_LABEL = 'salereport'
);

CREATE WORKLOAD CLASSIFIER classifierB
WITH (
    WORKLOAD_GROUP = 'wgUserQueries',
    MEMBERNAME = 'userloginA',
    IMPORTANCE = LOW,
    START_TIME = '18:00',
    END_TIME = '07:00'
);

The user userloginA is configured for both classifiers. If userloginA runs a query with a label equal to salesreport between 6PM and 7AM UTC, the request is classified to the wgDashboards workload group with HIGH importance. The expectation might be to classify the request to wgUserQueries with LOW importance for off-hours reporting, but the weighting of WLM_LABEL is higher than START_TIME/END_TIME. The weighting of classifierA is 80 (64 for the user, plus 16 for WLM_LABEL). The weighting of classifierB is 68 (64 for the user, 4 for START_TIME/END_TIME). In this case, you can add WLM_LABEL to classifierB.

For more information, see workload weighting.

Permissions

Requires CONTROL DATABASE permission.

Examples

The following example shows how to create a workload classifier named wgcELTRole. It uses the staticrc20 workload group, the user ELTRole, and sets the IMPORTANCE to ABOVE_NORMAL.

CREATE WORKLOAD CLASSIFIER wgcELTRole
WITH (
    WORKLOAD_GROUP = 'staticrc20',
    MEMBERNAME = 'ELTRole',
    IMPORTANCE = ABOVE_NORMAL
);

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