@@ -164,7 +164,7 @@ to support sharding:
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.. data:: config.changelog.what
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- Reflects the type of change recorded. Possible values include:
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+ The type of change recorded. Possible values include:
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- ``dropCollection``
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- ``dropCollection.start``
@@ -181,38 +181,48 @@ to support sharding:
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.. data:: config.changelog.details
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- A :term:`document` that contains additional details regarding
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+ A :term:`document` that contains additional details for
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the change. The structure of the :data:`~config.changelog.details`
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document depends on the type of change.
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.. data:: config.chunks
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.. include:: /includes/admonition-config-db-is-internal.rst
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- The :data:`~config.chunks` collection stores a document for each chunk in
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- the cluster. Consider the following example of a document for a
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- chunk named ``mydb.foo-a_\"cat\"``:
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+ The :data:`config.chunks` collection stores a document for each
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+ chunk in the cluster. The following example shows a document:
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.. code-block:: javascript
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{
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- "_id" : "mydb.foo-a_\"cat\"",
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- "lastmod" : Timestamp(2, 1),
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- "uuid": "c025d039-e626-435e-b2d2-c1d436038041",
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- "min" : {
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- "animal" : "cat"
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- },
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- "max" : {
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- "animal" : "dog"
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- },
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- "shard" : "shard0004",
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- "history" : [ { "validAfter" : Timestamp(1569368571, 27), "shard" : "shard0004" } ]
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+ _id: ObjectId('65a954c0de11596e08e7c1dc'),
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+ uuid: UUID('a4479215-a38d-478f-a82b-e5e95d455e55'),
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+ min: { a: Long('121204345') },
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+ max: { a: Long('993849349') },
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+ shard: 'shard01',
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+ lastmod: Timestamp({ t: 1, i: 0 }),
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+ history: [
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+ {
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+ validAfter: Timestamp({ t: 1705596095, i: 14 }),
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+ shard: 'shard01'
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+ }
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+ ]
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}
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- These documents store the range of values for the shard key that
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- describe the chunk in the ``min`` and ``max`` fields. Additionally
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- the ``shard`` field identifies the shard in the cluster that "owns"
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- the chunk.
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+ In the document:
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+
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+ - ``_id`` is the chunk identifier.
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+ - ``min`` and ``max`` are the range of values for the chunk's shard
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+ key.
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+ - ``shard`` is the name of the shard that stores the chunk in the
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+ cluster.
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+
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+ .. tip::
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+
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+ To find the chunks in a collection, retrieve the collection's
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+ ``uuid`` identifier from the :data:`config.collections`
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+ collection. Then, use ``uuid`` to retrieve the matching document
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+ with the same ``uuid`` from the ``config.chunks`` collection.
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.. data:: config.collections
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@@ -413,7 +423,7 @@ to support sharding:
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.. include:: /includes/admonition-config-db-is-internal.rst
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The :data:`~config.version` collection holds the current metadata version number. This
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- collection contains only one document. For example:
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+ collection contains only one document. For example:
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.. code-block:: javascript
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@@ -431,7 +441,7 @@ to support sharding:
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Collections to Support Sessions
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-------------------------------
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- Starting in MongoDB 3.6, the ``config`` database contains the
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+ The ``config`` database contains the
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*internal* collections to support :ref:`causally consistent sessions
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<sessions>` for standalones, replica sets, and sharded clusters and
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retryable writes and :ref:`transactions <transactions>` for
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