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This API is supported for first-generation runtimes and can be used when upgrading to corresponding second-generation runtimes. If you are updating to the App Engine Java 11/17 runtime, refer to the migration guide to learn about your migration options for legacy bundled services.Datastore maintains statistics about the data stored for an application, such as how many entities there are of a given kind, or how much space is used by property values of a given type. You can view these statistics in the Google Cloud console, in the Dashboard page.
You can also access these values programmatically within the application by querying for specially named entities using the Datastore API. Each statistic is accessible as an entity whose kind name begins and ends with two underscores. For example, each app has exactly one entity of the kind __Stat_Total__ that represents statistics about all of the entities in Datastore in total. Each statistic entity has the following properties:
count, the number of items considered by the statistic (a long integer)bytes, the total size of the items for this statistic (a long integer)timestamp, the time of the most recent update to the statistic (a date-time value)Some statistic kinds also have additional properties, listed below.
A Java application can access statistic entities using the low-level API. For example:
When the statistics system creates new statistic entities, it does not delete the old ones right away. The best way to get a consistent view of the statistics is to query for the __Stat_Total__ entity with the most recent timestamp, then use that timestamp value as a filter when fetching other statistic entities.
The statistic entities are included in the calculated statistic values. Statistic entities take up space relative to the number of unique kinds and property names used by the application.
The statistics system will also create statistics specific to each namespace Note that if an application does not use Datastore namespaces then namespace specific statistics will not be created. Namespace specific stats are found in the namespace that they're specific to. The kind names for namespace specific stats are prefixed with __Stat_Ns_ and have the same corresponding suffix as application wide statistics kinds.
Applications with thousands of namespaces, kinds, or property names require a very large number of statistics entities. To keep the overhead of storing and updating the statistics reasonable, Datastore progressively drops statistics entities, in the following order:
__Stat_Ns_PropertyName_Kind__, __Stat_Ns_PropertyType_PropertyName_Kind____Stat_PropertyName_Kind__, __Stat_PropertyType_PropertyName_Kind____Stat_Ns_Kind__, __Stat_Ns_Kind_IsRootEntity__, __Stat_Ns_Kind_NotRootEntity__, __Stat_Ns_PropertyType_Kind____Stat_Kind__, __Stat_Kind_IsRootEntity__, __Stat_Kind_NotRootEntity__, __Stat_PropertyType_Kind____Stat_Namespace__, __Stat_Ns_Kind_CompositeIndex__, __Stat_Ns_PropertyType__, __Stat_Ns_Total__The summary statistics entities (__Stat_Kind_CompositeIndex__, __Stat_PropertyType__, __Stat_Total__) are never dropped.
The complete list of available statistics is as follows:
Statistic Stat Entity Kind Description all entities__Stat_Total__
__Stat_Ns_Total__ All entities. Additional properties:
• entity_bytes: The storage in the entities table measured in bytes.
builtin_index_bytes: The storage in built-in index entries measured in bytes.
builtin_index_count: the count of built-in index entries.
composite_index_bytes: The storage in composite index entries measured in bytes.
composite_index_count: The count of composite index entries. all entities in a namespace __Stat_Namespace__
__Stat_Namespace__ entities are created for each namespace encountered and are only found in the empty string namespace. All entities in a namespace.
• subject_namespace, the namespace represented (a string)
entity_bytes: The storage in the entities table measured in bytes.
builtin_index_bytes: The storage in built-in index entries measured in bytes.
builtin_index_count: the count of built-in index entries.
composite_index_bytes: The storage in composite index entries measured in bytes.
composite_index_count: The count of composite index entries. all entries in application defined indexes __Stat_Kind_CompositeIndex__
__Stat_Ns_Kind_CompositeIndex__
• index_id, the index id.
kind_name, the name of the kind represented (a string) entities of a kind __Stat_Kind__
__Stat_Ns_Kind__ Entities of a kind; one stat entity for each kind of entity stored. Additional properties:
• kind_name, the name of the kind represented (a string)
entity_bytes: The storage in the entities table measured in bytes.
builtin_index_bytes: The storage in built-in index entries measured in bytes.
builtin_index_count: the count of built-in index entries.
composite_index_bytes: The storage in composite index entries measured in bytes.
composite_index_count: The count of composite index entries. root entities of a kind __Stat_Kind_IsRootEntity__
__Stat_Ns_Kind_IsRootEntity__ Entities of a kind that are entity group root entities (have no ancestor parent); one stat entity for each kind of entity stored. Additional properties:
• kind_name, the name of the kind represented (a string)
entity_bytes: The storage in the entities table measured in bytes. non-root entities of a kind __Stat_Kind_NotRootEntity__
__Stat_Ns_Kind_NotRootEntity__ Entities of a kind that are not entity group root entities (have an ancestor parent); one stat entity for each kind of entity stored. Additional properties:
• kind_name, the name of the kind represented (a string)
entity_bytes: The storage in the entities table measured in bytes. properties of a type __Stat_PropertyType__
__Stat_Ns_PropertyType__ Properties of a value type across all entities; one stat entity per value type. Additional properties:
• property_type, the name of the value type (a string)
entity_bytes: The storage in the entities table measured in bytes.
builtin_index_bytes: The storage in built-in index entries measured in bytes.
builtin_index_count: the count of built-in index entries. properties of a type per kind __Stat_PropertyType_Kind__
__Stat_Ns_PropertyType_Kind__ Properties of a value type across entities of a given kind; one stat entity per combination of property type and kind. Additional properties:
• property_type, the name of the value type (a string)
kind_name, the name of the kind represented (a string)
entity_bytes: The storage in the entities table measured in bytes.
builtin_index_bytes: The storage in the built-in index measured in bytes.
builtin_index_count: the count of built-in index entries. properties with a name __Stat_PropertyName_Kind__
__Stat_Ns_PropertyName_Kind__ Properties with a given name across entities of a given kind; one stat entity per combination of unique property name and kind. Additional properties:
• property_name, the name of the property (a string)
kind_name, the name of the kind represented (a string)
entity_bytes: The storage in the entities table measured in bytes.
builtin_index_bytes: The storage in built-in index entries measured in bytes.
builtin_index_count: the count of built-in index entries. properties of a type and with a name __Stat_PropertyType_PropertyName_Kind__
__Stat_Ns_PropertyType_PropertyName_Kind__ Properties with a given name and of a given value type across entities of a given kind; one stat entity per combination of property name, value type and kind that exists in Datastore. Additional properties:
• property_type, the name of the value type (a string)
property_name, the name of the property (a string)
kind_name, the name of the kind represented (a string)
entity_bytes: The storage in the entities table measured in bytes.
builtin_index_bytes: The storage in built-in index entries measured in bytes.
builtin_index_count: the count of built-in index entries.
Some statistics refer to Datastore property value types by name, as strings. These names are as follows:
"Blob""BlobKey""Boolean""Category""Date/Time""Email""Float""GeoPt""IM""Integer""Key""Link""NULL""PhoneNumber""PostalAddress""Rating""ShortBlob""String""Text""User"__Stat_Namespace__ entities contain the same information found in __Stat_Ns_Total__ records. __Stat_Namespace__ entities are stored in the empty namespace and contain a subject_namespace field describing the namespace to which they belong. __Stat_Ns_Total__ records are stored in the namespace to which they refer, and thus do not contain a subject_namespace field. Hence, a query on kind __Stat_Namespace__ (from the empty string namespace) ordered descending by bytes will list the namespaces that consume the largest storage first. Because queries across namespaces are not possible, any query for __Stat_Ns_Total__ entities will only ever produce at most a single record.
Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2025-08-07 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-07 UTC."],[[["This API provides access to Datastore statistics, which track data like entity counts and property value sizes, for application analysis."],["Datastore statistics are represented as specially named entities, accessible via the Datastore API, with each statistic entity including properties like `count`, `bytes`, and `timestamp`."],["Statistics are organized into different categories, including total statistics, namespace-specific statistics, and statistics specific to kinds, properties, and their types."],["Datastore progressively drops less critical statistics entities (e.g., per-namespace, per-kind, per-property) to manage storage overhead, while summary statistics like `__Stat_Total__` are always retained."],["The `__Stat_Namespace__` and `__Stat_Ns_Total__` entities both contain similar information, however they differ in their storage location and the presence of the `subject_namespace` field."]]],[]]
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