DOCSP-49568 Find Slow Queries with Profiler (#11900) (#12236)

Author: kennethdyer

content/manual/manual/source/administration/query.txt

@@ -54,6 +54,14 @@ For more information, see :ref:`indexes`.
 Tasks
 -----
 
+Troubleshooting
+~~~~~~~~~~~~~~~
+
+- :ref:`manual-find-slow-queries-with-database-profiler`
+
+Solutions
+~~~~~~~~~
+
 - :ref:`manual-create-an-index`
 
 Details
@@ -160,7 +168,7 @@ help you identify specific index usage issues, such as:
 
 Learn More
 ----------
-- :ref:`query-profiler`
+- :ref:`Atlas Query Profiler <query-profiler>`
 
 - :ref:`profiler`
 

content/manual/manual/source/tutorial/find-slow-queries-with-database-profiler.txt

@@ -0,0 +1,217 @@
+.. meta::
+   :description: Manage the database profiler to collect detailed information on database commands, affecting performance and disk use when enabled.
+
+.. contents:: On this page
+   :local:
+   :backlinks: none
+   :depth: 1
+   :class: singlecol
+
+.. _manual-find-slow-queries-with-database-profiler:
+
+=================
+Find Slow Queries
+=================
+
+MongoDB includes the :ref:`database-profiler`, which can
+identify slow queries and help you determine how to improve
+query performance.
+
+About This Task
+---------------
+
+Performance, Storage, and Security
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This task uses the database profiler to identify slow queries on
+a running :program:`mongod` instance. When enabled, the database
+profiler can affect performance and disk usage and expose
+unencrypted query data.
+
+.. warning::
+
+   Consider the performance, storage, and security implications
+   before using the database profiler on a production
+   deployment.
+
+Atlas Query Profiler
+~~~~~~~~~~~~~~~~~~~~
+
+Atlas users can take advantage of the Atlas Query Profiler to
+identify slow queries with the convenience of visualization
+through a scatterplot chart.
+
+For more information, see :ref:`query-profiler`.
+
+Slow Queries
+~~~~~~~~~~~~
+
+A slow query is one that takes longer than a specified amount of
+time to run. For this task, the slow query threshold is set to
+100 milliseconds.
+
+In some use cases, you may require queries run faster. In
+others, you may need to raise the threshold to focus only on
+those queries that are the slowest.
+
+Choose a slow query threshold that reflects your specific
+application and database needs.
+
+Context
+~~~~~~~
+
+When enabled, the database profiler monitors queries at a
+database-level only. If you need the profiler to monitor slow
+queries on multiple databases, run the
+:method:`db.setProfilingLevel` method on each database.
+
+Sharded Clusters
+~~~~~~~~~~~~~~~~
+
+The database profiler is not available through
+:program:`mongos`.
+
+Steps
+-----
+
+.. procedure::
+   :style: normal
+
+   .. step:: Enable the database profiler.
+
+      To enable the database profiler to monitor slow queries,
+      use the :method:`db.setProfilingLevel` method:
+
+      .. io-code-block:: 
+
+         .. input::
+            :language: js
+
+            db.setProfilingLevel(1, 100)
+
+         .. output::
+            :language: js
+
+            { was: 0, slowms: 1, sampleRate: 1, ok: 1}
+
+      This sets the profiling level to ``1``, which monitors for
+      slow queries, and defines a query as slow if it takes
+      longer than 100 milliseconds to run.
+
+   .. step:: Check for slow queries.
+
+      To list any slow queries found by the database profiler,
+      query the :data:`system.profile <<database>.system.profile>`
+      collection for relevant data:
+
+      .. io-code-block:: 
+
+         .. input::
+            :language: js
+
+            db.system.profile.find( { },
+               {
+                  command: 1,
+                  millis: 1,
+                  docsExamined: 1,
+                  keysExamined: 1,
+                  nreturned: 1
+               }
+            ).sort( { ts: -1 } )
+
+         .. output::
+            :language: js
+
+            [
+               {
+                  command: {
+                     find: 'people',
+                     filter: { age: { '$gt': 35 } },
+                     lsid: { id: UUID('ae3e9932-0a78-47ab-b741-01dd3bfb3563') },
+                     '$db': 'contacts'
+                  },
+                  keysExamined: 0,
+                  docsExamined: 100000,
+                  nreturned: 40,
+                  millis: 143
+               }
+            ]
+
+      The command provides a list of slow queries observed by
+      the database profiler. 
+
+      The projection filters the return documents to include
+      information that you may find useful in determining what
+      caused the query to run slow.
+
+      - If ``keysExamined`` is ``0``, it indicates that an index
+        was not used by the query. To solve this, :ref:`create
+        an index <manual-create-an-index>` on the collection.
+
+      - If an index was used and ``docsExamined`` is much larger
+        than ``nreturned``, it indicates an ineffectual index.
+        You may need to update the index or create a new one on
+        a field or fields used by the query filter.
+
+      - If ``keysExamined`` is high and ``docsExamined`` is low,
+        it indicates effective index use.
+
+   .. step:: Disable the database profiler.
+
+      To ensure that the database profiler does not further
+      disrupt performance, disable it when it's no longer
+      needed:
+
+      .. io-code-block:: 
+
+         .. input::
+            :language: javascript
+
+            db.setProfilingLevel(0)
+
+         .. output::
+            :language: javascript
+
+            { was: 1, slowms: 1, sampleRate: 1, ok: 1}
+
+Examples
+--------
+
+Ignore Indexes
+~~~~~~~~~~~~~~
+
+To evaluate performance on a collection with an index, you can
+set the query to ignore indexes using the :method:`hint( {
+$natural: 1 } ) <cursor.hint>` method.
+
+.. code-block:: javascript
+
+   db.listingsAndReviews.find( {
+      $or: [
+         { "address.market": "Berlin" },
+         { "review_scores.review_scores_cleanliness": { $lt: 5 } }
+      ],
+      $where: function () {
+         return this.amenities && this.amenities.length > 15;
+      } 
+   } ).sort( { description: 1 } ).hint( { $natural: 1 } );
+
+You may find this useful in cases where you want to compare how
+queries perform with a collection scan to that of an index scan.
+
+Next Steps
+----------
+
+- :ref:`manual-create-an-index`
+ 
+Learn More
+----------
+
+- :ref:`query-performance`
+
+- :ref:`Atlas Query Profiler <query-profiler>`
+
+- :ref:`database-profiler`
+
+- :ref:`indexes`
+

content/manual/manual/source/tutorial/manage-the-database-profiler.txt

@@ -526,3 +526,4 @@ For more information, see :doc:`/tutorial/perform-maintence-on-replica-set-membe
    :hidden:
 
    Output </reference/database-profiler>
+   Find Slow Queries </tutorial/find-slow-queries-with-database-profiler>

content/manual/v6.0/source/administration/query.txt

@@ -54,6 +54,14 @@ For more information, see :ref:`indexes`.
 Tasks
 -----
 
+Troubleshooting
+~~~~~~~~~~~~~~~
+
+- :ref:`manual-find-slow-queries-with-database-profiler`
+
+Solutions
+~~~~~~~~~
+
 - :ref:`manual-create-an-index`
 
 Details
@@ -160,7 +168,7 @@ help you identify specific index usage issues, such as:
 
 Learn More
 ----------
-- :ref:`query-profiler`
+- :ref:`Atlas Query Profiler <query-profiler>`
 
 - :ref:`profiler`