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- PlanCache.getPlansByQuery()
PlanCache.getPlansByQuery()¶
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Definition¶
-
PlanCache.
getPlansByQuery
(<query>, <projection>, <sort>)¶ Deprecated since version 4.2.
Note
MongoDB 4.2 adds a new aggregation pipeline stage
$planCacheStats
that provides plan cache information for a collection.The
$planCacheStats
aggregation stage is preferred over the following methods and commands, which have been deprecated in 4.2:PlanCache.getPlansByQuery()
method/planCacheListPlans
command, andPlanCache.listQueryShapes()
method/planCacheListQueryShapes
command.
Displays the cached query plans for the specified query shape.
To help identify slow queries with the same query shape, starting in MongoDB 4.2, each query shape is associated with a queryHash. The
queryHash
is a hexadecimal string that represents a hash of the query shape and is dependent only on the query shape.Note
As with any hash function, two different query shapes may result in the same hash value. However, the occurrence of hash collisions between different query shapes is unlikely.
The query optimizer only caches the plans for those query shapes that can have more than one viable plan.
The method is only available from the
plan cache object
of a specific collection; i.e.The
PlanCache.getPlansByQuery()
method accepts the following parameters:Parameter Type Description query
document The query predicate of the query shape. Only the structure of the predicate, including the field names, are significant to the shape; the values in the query predicate are insignificant. projection
document Optional. The projection associated with the query shape. Required if specifying the sort
parameter.sort
document Optional. The sort associated with the query shape. Returns: Array of cached query plans for a query shape. To see the query shapes for which cached query plans exist, see List Query Shapes.
The
PlanCache.getPlansByQuery()
method returns the same output as theplanCacheListPlans
database command.
Required Access¶
On systems running with authorization
, a user must have access that
includes the planCacheRead
action.
Example¶
If a collection orders
has the following query shape:
The following operation displays the query plan cached for the shape: