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sys.query_store_plan (Transact-SQL)

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Applies to: SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics

Contains information about each execution plan associated with a query.

Column name Data type Description
plan_id bigint Primary key.
query_id bigint Foreign key. Joins to sys.query_store_query (Transact-SQL).
plan_group_id bigint ID of the plan group. Cursor queries typically require multiple (populate and fetch) plans. Populate and fetch plans that are compiled together are in the same group.

0 means plan is not in a group.
engine_version nvarchar(32) Version of the engine used to compile the plan in 'major.minor.build.revision' format.
compatibility_level smallint Database compatibility level of the database referenced in the query.
query_plan_hash binary(8) MD5 hash of the individual plan.
query_plan nvarchar(max) Showplan XML for the query plan.
is_online_index_plan bit Plan was used during an online index build.
Note: Azure Synapse Analytics always returns zero (0).
is_trivial_plan bit Plan is a trivial plan (output in stage 0 of query optimizer).
Note: Azure Synapse Analytics always returns zero (0).
is_parallel_plan bit Plan is parallel.
Note: Azure Synapse Analytics always returns one (1).
is_forced_plan bit Plan is marked as forced when user executes stored procedure sys.sp_query_store_force_plan. Forcing mechanism does not guarantee that exactly this plan will be used for the query referenced by query_id. Plan forcing causes query to be compiled again and typically produces exactly the same or similar plan to the plan referenced by plan_id. If plan forcing does not succeed, force_failure_count is incremented and last_force_failure_reason is populated with the failure reason.
Note: Azure Synapse Analytics always returns zero (0).
is_natively_compiled bit Plan includes natively compiled memory optimized procedures. (0 = FALSE, 1 = TRUE).
Note: Azure Synapse Analytics always returns zero (0).
force_failure_count bigint Number of times that forcing this plan has failed. It can be incremented only when the query is recompiled (not on every execution). It is reset to 0 every time is_plan_forced is changed from FALSE to TRUE.
Note: Azure Synapse Analytics always returns zero (0).
last_force_failure_reason int Reason why plan forcing failed.

0: no failure, otherwise error number of the error that caused the forcing to fail

8637: ONLINE_INDEX_BUILD

8675: OPTIMIZATION_REPLAY_FAILED

8683: INVALID_STARJOIN

8684: TIME_OUT

8689: NO_DB

8690: HINT_CONFLICT

8691: SETOPT_CONFLICT

8694: DQ_NO_FORCING_SUPPORTED

8698: NO_PLAN

8712: NO_INDEX

8713: VIEW_COMPILE_FAILED

<other value>: GENERAL_FAILURE
Note: Azure Synapse Analytics always returns zero (0).
last_force_failure_reason_desc nvarchar(128) Textual description of last_force_failure_reason.

ONLINE_INDEX_BUILD: query tries to modify data while target table has an index that is being built online

OPTIMIZATION_REPLAY_FAILED: The optimization replay script failed to execute.

INVALID_STARJOIN: plan contains invalid StarJoin specification

TIME_OUT: Optimizer exceeded number of allowed operations while searching for plan specified by forced plan

NO_DB: A database specified in the plan does not exist

HINT_CONFLICT: Query cannot be compiled because plan conflicts with a query hint

DQ_NO_FORCING_SUPPORTED: Cannot execute query because plan conflicts with use of distributed query or full-text operations.

NO_PLAN: Query processor could not produce query plan because forced plan could not be verified to be valid for the query

NO_INDEX: Index specified in plan no longer exists

VIEW_COMPILE_FAILED: Could not force query plan because of a problem in an indexed view referenced in the plan

GENERAL_FAILURE: general forcing error (not covered with other reasons)
Note: Azure Synapse Analytics always returns NONE.
count_compiles bigint Plan compilation statistics.
initial_compile_start_time datetimeoffset Plan compilation statistics.
last_compile_start_time datetimeoffset Plan compilation statistics.
last_execution_time datetimeoffset Last execution time refers to the last end time of the query/plan.
avg_compile_duration float Plan compilation statistics, in microseconds. Divide by 1000000 to get seconds.
last_compile_duration bigint Plan compilation statistics, in microseconds. Divide by 1000000 to get seconds.
plan_forcing_type int Plan forcing type.

0: NONE

1: MANUAL

2: AUTO
plan_forcing_type_desc nvarchar(60) Text description of plan_forcing_type.

NONE: No plan forcing

MANUAL: Plan forced by user

AUTO: Plan forced by automatic tuning.
has_compile_replay_script bit Applies to: SQL Server (Starting with SQL Server 2022 (16.x))

Indicates whether the plan has an optimization replay script associated with it:

0 = No optimization replay script (none or even invalid).

1 = optimization replay script recorded.

Not applicable to Azure Synapse Analytics.
is_optimized_plan_forcing_disabled bit Applies to: SQL Server (Starting with SQL Server 2022 (16.x))

Indicates whether optimized plan forcing was disabled for the plan:

0 = disabled.

1 = not disabled.

Not applicable to Azure Synapse Analytics.
plan_type int Applies to: SQL Server (Starting with SQL Server 2022 (16.x))

Plan type.

0: Compiled Plan

1: Dispatcher Plan

2: Query Variant Plan

Not applicable to Azure Synapse Analytics.
plan_type_desc nvarchar(120) Applies to: SQL Server (Starting with SQL Server 2022 (16.x))

Text description of the plan type.

Compiled Plan: Indicates that the plan is a non-parameter sensitive plan optimized plan

Dispatcher Plan: Indicates that the plan is a parameter sensitive plan optimized dispatcher plan

Query Variant Plan: Indicates that the plan is a parameter sensitive plan optimized query variant plan

Not applicable to Azure Synapse Analytics.

Remarks

More than one plan can be forced when Query Store for secondary replicas is enabled.

In Azure Synapse Analytics, using columns has_compile_replay_script, is_optimized_plan_forcing_disabled, plan_type, plan_type_desc will result in an Invalid Column Name error as they are not supported. See Example B for an example of how to use sys.query_store_plan in Azure Synapse Analytics .

Plan forcing limitations

Query Store has a mechanism to enforce Query Optimizer to use certain execution plan. However, there are some limitations that can prevent a plan to be enforced.

First, if the plan contains following constructions:

  • Insert bulk statement.
  • Reference to an external table
  • Distributed query or full-text operations
  • Use of Global queries
  • Dynamic or keyset cursors
  • Invalid star join specification

Note

Azure SQL Database and SQL Server 2019 and later build versions support plan forcing for static and fast forward cursors.

Second, when objects that plan relies on, are no longer available:

  • Database (if Database, where plan originated, does not exist anymore)
  • Index (no longer there or disabled)

Finally, problems with the plan itself:

  • Not legal for query
  • Query Optimizer exceeded number of allowed operations
  • Incorrectly formed plan XML

Permissions

Requires the VIEW DATABASE STATE permission.

Examples

A. Find the reason SQL Server couldn't force a plan via QDS

Pay attention to the last_force_failure_reason_desc and force_failure_count columns:

SELECT TOP 1000
      p.query_id
       , p.plan_id
       , p.last_force_failure_reason_desc
       , p.force_failure_count
       , p.last_compile_start_time
       , p.last_execution_time
       , q.last_bind_duration
       , q.query_parameterization_type_desc
       , q.context_settings_id
       , c.set_options
       , c.status
    FROM sys.query_store_plan p
    JOIN sys.query_store_query q ON p.query_id = q.query_id
       JOIN sys.query_context_settings c ON c.context_settings_id = q.context_settings_id
       LEFT JOIN sys.query_store_query_text t ON q.query_text_id = t.query_text_id
    WHERE p.is_forced_plan = 1 and p.last_force_failure_reason != 0;

B. Query to view query plan results in Azure Synapse Analytics

Use the following sample query to find the 100 most recent execution plans in the Query Store in Azure Synapse Analytics.

SELECT TOP 100
      plan_id
      ,query_id
      ,plan_group_id
      ,engine_version
      ,compatibility_level
      ,query_plan_hash
      ,query_plan
      ,is_online_index_plan
      ,is_trivial_plan
      ,is_parallel_plan
      ,is_forced_plan
      ,is_natively_compiled
      ,force_failure_count
      ,last_force_failure_reason
      ,last_force_failure_reason_desc
      ,count_compiles
      ,initial_compile_start_time
      ,last_compile_start_time
      ,last_execution_time
      ,avg_compile_duration
      ,last_compile_duration
      ,plan_forcing_type
      ,plan_forcing_type_desc
  FROM sys.query_store_plan
  ORDER BY last_execution_time DESC;

Next steps

Learn more about Query Store and related concepts in the following articles: