Datastore statistics

Firestore in Datastore mode (Datastore) maintains statistics about the data that you store in an application, such as how many entities there are, of what 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 one of the following ways:

  • On the Dashboard page.
  • On the Entities page, run a GQL query in the form of SELECT * FROM __Stat_Kind__.
  • Programmatically within the application by querying for specially named entities using the Datastore API. For more information about the Datastore API, see APIs & Reference.

Datastore uses kind names that begin and end with two underscores to identify special entities that provide statistics about your data. These are called statistics entities. For example, each app has one entity of the kind __Stat_Total__, which represents statistics about all of the entities in a Datastore mode database.

Statistics entities track information about your data and give you insights into your data usage. They are automatically created. 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)

Each entity belongs to a specific kind. Statistics kind indicates the category of statistics being collected or used. Use the kind to identify the purpose of a statistic, such as optimizing a query, improving performance, or data analysis.

Some statistic kinds also have additional properties listed in the List of statistics section of this document.

When the statistics system creates new statistic entities, it doesn't delete the previous statistic entities right away. The best way to get a consistent view of the statistics is to query for the statistic entity with the most recent timestamp, then use that timestamp value as a filter when you fetch other statistic entities.

The statistics system also creates statistics that are specific to each namespace. The kind names of namespace-specific statistics are prefixed with __Stat_Ns__, followed by the same suffixes as the kind names of statistics that apply to the whole application.

If an application doesn't use namespaces, the statistics system won't create namespace-specific statistics. You can only find namespace-specific statistics in the namespace that they're relevant to.

List of statistics

The following is a list of available statistics:

Statistic Stat Entity Kind Description
all entities __Stat_Total__
Namespace specific entry:
__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__
Note that __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.

For more information, see the Statistics limitations section of this document.
all entries in application defined indexes __Stat_Kind_CompositeIndex__
Namespace specific entry: __Stat_Ns_Kind_CompositeIndex__
 Entries in the composite index table; one stat entity for each kind of entity stored. Additional properties:

• index_id: the index ID.
• kind_name: the name of the kind represented (a string)
entities of a kind __Stat_Kind__
Namespace specific entry:
__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__
Namespace specific entry:
__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__
Namespace specific entry:
__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__
Namespace specific entry:
__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__
Namespace specific entry:
__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.

For more information, see the Statistics limitations section of this document.
properties with a name __Stat_PropertyName_Kind__
Namespace specific entry:
__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__
Namespace specific entry:
__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 the database.

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.

For more information, see the Statistics limitations section of this document.

Some statistics refer to 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"

Statistics limitations

Statistics have the following limitations:

  • The __Stat_PropertyType_Kind__ property and the __Stat_PropertyType_PropertyName_Kind__ property return property type metadata for array value types, and separately record the property type for each value in the array. For example, if an array property stores a list of strings, the property records the property type as STRING, while the actual property type is ARRAY<STRING>.
  • The __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 don't 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. Since queries across namespaces are not possible, any query for __Stat_Ns_Total__ entities will only ever produce at most a single record.

Statistics entities drop order

Applications with thousands of namespaces, kinds, or property names require a large number of statistics entities. To reduce the overhead of storing and updating the statistics, Firestore in Datastore mode databases progressively drop statistics entities according to the order listed later.

The summary statistics entities __Stat_Kind_CompositeIndex__, __Stat_PropertyType__, and __Stat_Total__ are never dropped.

Statistics entities are dropped in groups in the following default order:

  1. per-namespace, per-kind, and per-property statistics:

    • __Stat_Ns_PropertyName_Kind__
    • __Stat_Ns_PropertyType_PropertyName_Kind__

  2. per-kind and per-property statistics

    • __Stat_PropertyName_Kind__
    • __Stat_PropertyType_PropertyName_Kind__

  3. per-namespace statistics

    • __Stat_Namespace__
    • __Stat_Ns_Kind_CompositeIndex__
    • __Stat_Ns_PropertyType__
    • __Stat_Ns_Total__

Kind statistics entities have the following drop order:

  1. per-namespace, per-kind statistics

    • __Stat_Ns_Kind__
    • __Stat_Ns_Kind_IsRootEntity__
    • __Stat_Ns_Kind_NotRootEntity__
    • __Stat_Ns_PropertyType_Kind__

  2. per-kind statistics

    • __Stat_Kind__
    • __Stat_Kind_IsRootEntity__
    • __Stat_Kind_NotRootEntity__
    • __Stat_PropertyType_Kind__

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