Merge pull request #284264 from gmndrg/main

Updates for field mappings - including index projections scenarios

Author: prmerger-automator[bot]

articles/search/search-indexer-field-mappings.md

@@ -11,7 +11,7 @@ ms.service: cognitive-search
 ms.custom:
   - ignite-2023
 ms.topic: how-to
-ms.date: 07/29/2024
+ms.date: 08/09/2024
 ---
 
 # Field mappings and transformations using Azure AI Search indexers
@@ -30,8 +30,8 @@ Field mappings apply to:
 
 + Physical data structures on both sides of the data path. Logical data structures created by skills reside only in memory. Use [outputFieldMappings](cognitive-search-output-field-mapping.md) to map in-memory nodes to output fields in a search index.
 
-+ Search indexes only. To populate a [knowledge store](knowledge-store-concept-intro.md), use [projections](knowledge-store-projections-examples.md) for data path configuration.
-
++ Parent AI Search indexes only. For "secondary" indexes with "child" documents or "chunks", refer to the [advanced field mapping scenarios](#advancedFieldMappingScenarios).
+  
 + Top-level search fields only, where the `targetFieldName` is either a simple field or a collection. A target field can't be a complex type.
 
 ## Supported scenarios
@@ -449,6 +449,27 @@ The field mapping needs to be specified as shown below.
 ]
  ```
 
+<a name="advancedFieldMappingScenarios"></a>
+## Advanced field mapping scenarios
+
+In scenarios where you have "one-to-many" document relationships, such as data chunking or splitting, follow these guidelines for mapping fields from parent documents to "child" documents (chunks):
+
+### 1. Skipping parent document indexing
+
+If you are skipping the indexing of parent documents (by setting `projectionMode` to `skipIndexingParentDocuments` in the skillset's `indexProjections`), use [index projections](index-projections-concept-intro.md) to map fields from the parent documents to the "child" documents.
+
+### 2. Indexing both parent and "child" documents
+
+If you are indexing both parent documents and "child" documents:
++ Use field mappings to map fields to the parent documents.
++ Use [index projections](index-projections-concept-intro.md) to map fields to the "child" documents.
+
+### 3. Mapping function-transformed values to parent and/or "child" documents
+
+If a field in the parent document requires a transformation (using the [mapping functions](#mappingFunctions) such as encoding) and needs to be mapped to the parent and/or "child" documents:
++ Apply the transformation using field mappings' [functions](#mappingFunctions) in the indexer.
++ Use [index projections](index-projections-concept-intro.md) in the skillset to map the transformed field to the "child" documents.
+
 ## See also
 
 + [Supported data types in Azure AI Search](/rest/api/searchservice/supported-data-types)