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DOCS-8478: Size and Count accuracy in WT after unexpected shutdown #2712

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DOCS-8478: Size and Count accuracy in WT after unexpected shutdown #2712

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6 changes: 4 additions & 2 deletions source/includes/fact-unexpected-shutdown-accuracy.rst
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Expand Up @@ -6,8 +6,10 @@ The amount of drift depends on the number of insert, update, or delete
operations performed between the last :ref:`checkpoint
<storage-wiredtiger-checkpoints>` and the unclean shutdown. Checkpoints
usually occur every 60 seconds. However, :program:`mongod` instances running
with non-default :option:`syncDelay` settings may have more or less frequent
with non-default :option:`--syncdelay` settings may have more or less frequent
checkpoints.

Run :dbcommand:`validate` on each collection on the :program:`mongod` to
to restore the correct statistics after an unclean shutdown.
to restore the correct statistics after an unclean shutdown. If multiple
:program:`mongod` instances experienced an unclean shutdown, perform the
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Somewhat on the fence on this second sentence. Can remove if necessary

validation procedure on each :program:`mongod`.
17 changes: 11 additions & 6 deletions source/reference/command/count.txt
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Expand Up @@ -44,12 +44,17 @@ Behavior

.. include:: /includes/extracts/fact-count-on-sharded-clusters-cmd-count.rst

For MongoDB instances using the :doc:`WiredTiger </core/wiredtiger>`
storage engine, after an unclean shutdown, statistics on size and count
may off by up to 1000 documents as reported by :dbcommand:`collStats`,
:dbcommand:`dbStats`, :dbcommand:`count`. To restore the correct
statistics for the collection, run :dbcommand:`validate` on the
collection.
Accuracy after Unexpected Shutdown
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. |cmd| replace:: :dbcommand:`count`
.. |opt| replace:: count

.. include:: /includes/fact-unexpected-shutdown-accuracy.rst

.. note::
This loss of accuracy only applies to :dbcommand:`count`
operations that do *not* include a query document.

Examples
--------
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13 changes: 7 additions & 6 deletions source/reference/command/dbStats.txt
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Expand Up @@ -45,12 +45,13 @@ The time required to run the command depends on the total size of the
database. Because the command must touch all data files, the command
may take several seconds to run.

For MongoDB instances using the :doc:`WiredTiger </core/wiredtiger>`
storage engine, after an unclean shutdown, statistics on size and count
may off by up to 1000 documents as reported by :dbcommand:`collStats`,
:dbcommand:`dbStats`, :dbcommand:`count`. To restore the correct
statistics for the collection, run :dbcommand:`validate` on the
collection.
Accuracy after Unexpected Shutdown
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. |cmd| replace:: :dbcommand:`dbStats`
.. |opt| replace:: count and size

.. include:: /includes/fact-unexpected-shutdown-accuracy.rst

.. _dbstats-output:

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10 changes: 9 additions & 1 deletion source/reference/method/db.collection.stats.txt
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Expand Up @@ -49,10 +49,18 @@ by ``scale``.
.. note::

The scale factor rounds values to whole numbers.

Depending on the storage engine, the data returned may differ. For details on
the fields, see :ref:`output details <collStats-output>`.

Accuracy after Unexpected Shutdown
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. |cmd| replace:: :method:`db.collection.stats()`
.. |opt| replace:: count and size

.. include:: /includes/fact-unexpected-shutdown-accuracy.rst

Index Filter Behavior
~~~~~~~~~~~~~~~~~~~~~

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13 changes: 7 additions & 6 deletions source/reference/method/db.stats.txt
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Expand Up @@ -31,12 +31,13 @@ Description
Behavior
--------

For MongoDB instances using the :doc:`WiredTiger </core/wiredtiger>`
storage engine, after an unclean shutdown, statistics on size and count
may off by up to 1000 documents as reported by :dbcommand:`collStats`,
:dbcommand:`dbStats`, :dbcommand:`count`. To restore the correct
statistics for the collection, run :dbcommand:`validate` on the
collection.
Accuracy after Unexpected Shutdown
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. |cmd| replace:: :method:`db.stats`
.. |opt| replace:: count and size

.. include:: /includes/fact-unexpected-shutdown-accuracy.rst

Example
-------
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