DOCSP 24995 documenting performance degradation of bulk inserts (#5141) (#5286)

* DOCSP-24995 documenting performance degredation of bulk random insert

* DOCSP-24995 small wording changes

* DOCSP-24995 small wording changes

* DOCSP-24995 small wording changes

* DOCSP-24995 small wording changes

* DOCSP-24995 rephrase

* DOCSP-24995 rephrase

* DOCSP-24995 copy edits

* DOCSP-24995 copy edits

* DOCSP-24995 copy edits

* DOCSP-24995 copy edits

* DOCSP-24995 copy edits

* DOCSP-24995 tech edit

Author: ltran-mdb2

source/faq/indexes.txt

@@ -116,3 +116,8 @@ Write operations may require updates to indexes:
 
 Therefore, if your application is write-heavy, indexes might affect
 performance.
+
+How does random data impact index performance?
+----------------------------------------------
+
+.. include:: /includes/indexes/random-data-performance.rst

source/includes/indexes/random-data-performance.rst

@@ -0,0 +1,17 @@
+If an operation inserts a large amount of random data (for example,
+hashed indexes) on an indexed field, insert performance may decrease.
+Bulk inserts of random data create random index entries, which increase
+the size of the index. If the index reaches the size that requires each
+random insert to access a different index entry, the inserts result in a
+high rate of WiredTiger cache eviction and replacement. When this
+happens, the index is no longer fully in cache and is updated on disk,
+which decreases performance.
+
+To improve the performance of bulk inserts of random data on indexed
+fields, you can either: 
+
+- Drop the index, then recreate it after you insert the random data.
+- Insert the data into an empty unindexed collection.
+
+Creating the index after the bulk insert sorts the data in memory and
+performs an ordered insert on all indexes. 

source/reference/method/Bulk.insert.txt

@@ -49,6 +49,11 @@ Insert Inaccuracies
 
 .. |writeResult| replace:: :data:`BulkWriteResult.nInserted`
 
+Performance Consideration for Random Data
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. include:: /includes/indexes/random-data-performance.rst
+
 Example
 -------
 

source/reference/method/db.collection.insertMany.txt

@@ -173,6 +173,10 @@ Write Concerns and Transactions
 
 .. |operation| replace:: :method:`db.collection.insertMany()`
 
+Performance Consideration for Random Data
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. include:: /includes/indexes/random-data-performance.rst
 
 .. _insertMany-examples: