Merge pull request #102632 from MarkHeff/adlsgen2folders

Add info about folder changes

Author: PRMerger9

articles/search/search-howto-index-azure-data-lake-storage.md

@@ -44,4 +44,11 @@ Indexing content in Data Lake Storage Gen2 is identical to indexing content in A
 
 Azure Data Lake Storage Gen2 implements an [access control model](https://docs.microsoft.com/azure/storage/blobs/data-lake-storage-access-control) that supports both Azure role-based access control (RBAC) and POSIX-like access control lists (ACLs). When indexing content from Data Lake Storage Gen2, Azure Cognitive Search will not extract the RBAC and ACL information from the content. As a result, this information will not be included in your Azure Cognitive Search index.
 
-If maintaining access control on each document in the index is important, it is up to the application developer to implement [security trimming](https://docs.microsoft.com/azure/search/search-security-trimming-for-azure-search).
+If maintaining access control on each document in the index is important, it is up to the application developer to implement [security trimming](https://docs.microsoft.com/azure/search/search-security-trimming-for-azure-search).
+
+## Change Detection
+
+The Data Lake Storage Gen2 indexer supports change detection. This means that when the indexer runs it only reindexes the changed blobs as determined by the blob's `LastModified` timestamp.
+
+> [!NOTE] 
+> Data Lake Storage Gen2 allows directories to be renamed. When a directory is renamed the timestamps for the blobs in that directory do not get updated. As a result, the indexer will not reindex those blobs. If you need the blobs in a directory to be reindexed after a directory rename because they now have new URLs, you will need to update the `LastModified` timestamp for all the blobs in the directory so that the indexer knows to reindex them during a future run.