[Backport 2.11] [DOC]Add new dot expander processor doc

_ingest-pipelines/processors/dot-expander.md

@@ -0,0 +1,373 @@
+---
+layout: default
+title: Dot expander
+parent: Ingest processors
+nav_order: 65
+---
+
+# Dot expander 
+
+The `dot_expander` processor is a tool that helps you work with hierarchical data. It transforms fields containing dots into object fields, making them accessible to other processors in the pipeline. Without this transformation, fields with dots cannot be processed.
+
+The following is the syntax for the `dot_expander` processor:
+
+```json
+{
+  "dot_expander": {
+    "field": "field.to.expand" 
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Configuration parameters
+
+The following table lists the required and optional parameters for the `dot_expander` processor.
+
+Parameter | Required/Optional | Description |
+|-----------|-----------|-----------|
+`field`  | Required  | The field to be expanded into an object field. |
+`path` | Optional | This field is only required if the field to be expanded is nested within another object field. This is because the `field` parameter only recognizes leaf fields. |
+`description`  | Optional  | A brief description of the processor. |
+`if` | Optional | A condition for running the processor. |
+`ignore_failure` | Optional | If set to `true`, failures are ignored. Default is `false`. |
+`on_failure` | Optional | A list of processors to run if the processor fails. |
+`tag` | Optional | An identifier tag for the processor. Useful for debugging in order to distinguish between processors of the same type. |
+
+## Using the processor
+
+Follow these steps to use the processor in a pipeline.
+
+### Step 1: Create a pipeline
+
+The following query creates a `dot_expander` processor that will expand two fields named `user.address.city` and `user.address.state` into nested objects:
+
+```json
+PUT /_ingest/pipeline/dot-expander-pipeline
+{
+  "description": "Dot expander processor",
+  "processors": [
+    {
+      "dot_expander": {
+        "field": "user.address.city"
+      }
+    },
+    {
+      "dot_expander":{
+       "field": "user.address.state"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+### Step 2 (Optional): Test the pipeline
+
+It is recommended that you test your pipeline before you ingest documents.
+{: .tip}
+
+To test the pipeline, run the following query:
+
+```json
+POST _ingest/pipeline/dot-expander-pipeline/_simulate
+{
+  "docs": [
+    {
+      "_index": "testindex1",
+      "_id": "1",
+      "_source": {
+        "user.address.city": "New York",
+        "user.address.state": "NY"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The following example response confirms that the pipeline is working as expected:
+
+```json
+{
+  "docs": [
+    {
+      "doc": {
+        "_index": "testindex1",
+        "_id": "1",
+        "_source": {
+          "user": {
+            "address": {
+              "city": "New York",
+              "state": "NY"
+            }
+          }
+        },
+        "_ingest": {
+          "timestamp": "2024-01-17T01:32:56.501346717Z"
+        }
+      }
+    }
+  ]
+}
+```
+
+### Step 3: Ingest a document
+
+The following query ingests a document into an index named `testindex1`:
+
+```json
+PUT testindex1/_doc/1?pipeline=dot-expander-pipeline
+{
+  "user.address.city": "Denver",
+  "user.address.state": "CO"
+}
+```
+{% include copy-curl.html %}
+
+### Step 4 (Optional): Retrieve the document
+
+To retrieve the document, run the following query:
+
+```json
+GET testindex1/_doc/1
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The following response confirms that the specified fields were expanded into nested fields:
+
+```json
+{
+  "_index": "testindex1",
+  "_id": "1",
+  "_version": 1,
+  "_seq_no": 3,
+  "_primary_term": 1,
+  "found": true,
+  "_source": {
+    "user": {
+      "address": {
+        "city": "Denver",
+        "state": "CO"
+      }
+    }
+  }
+}
+```
+
+## The `path` parameter
+
+You can use the `path` parameter to specify the path to a dotted field within an object. For example, the following pipeline specifies the `address.city` field that is located within the `user` object: 
+
+```json
+PUT /_ingest/pipeline/dot-expander-pipeline
+{
+  "description": "Dot expander processor",
+  "processors": [
+    {
+      "dot_expander": {
+        "field": "address.city",
+        "path": "user"
+      }
+    },
+    {
+      "dot_expander":{
+       "field": "address.state",
+       "path": "user"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+You can simulate the pipeline as follows: 
+
+```json
+POST _ingest/pipeline/dot-expander-pipeline/_simulate
+{
+  "docs": [
+    {
+      "_index": "testindex1",
+      "_id": "1",
+      "_source": {
+        "user": {
+          "address.city": "New York",
+          "address.state": "NY"
+        }
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+The `dot_expander` processor transforms the document into the following structure:
+
+```json
+{
+  "user": {
+    "address": {
+      "city": "New York",
+      "state": "NY"
+    }
+  }
+}
+```
+
+## Field name conflicts
+
+If a field already exists with the same path as the path to which the `dot_expander` processor should expand the value, the processor merges the two values into an array.
+
+Consider the following pipeline that expands the field `user.name`:
+
+```json
+PUT /_ingest/pipeline/dot-expander-pipeline
+{
+  "description": "Dot expander processor",
+  "processors": [
+    {
+      "dot_expander": {
+        "field": "user.name"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+You can simulate the pipeline with a document containing two values with the exact same path `user.name`:
+
+```json
+POST _ingest/pipeline/dot-expander-pipeline/_simulate
+{
+  "docs": [
+    {
+      "_index": "testindex1",
+      "_id": "1",
+      "_source": {
+        "user.name": "John", 
+        "user": {
+          "name": "Steve"
+        }
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+The response confirms that the values were merged into an array:
+
+```json
+{
+  "docs": [
+    {
+      "doc": {
+        "_index": "testindex1",
+        "_id": "1",
+        "_source": {
+          "user": {
+            "name": [
+              "Steve",
+              "John"
+            ]
+          }
+        },
+        "_ingest": {
+          "timestamp": "2024-01-17T01:44:57.420220551Z"
+        }
+      }
+    }
+  ]
+}
+```
+
+If a field contains the same name but a different path, then the field needs to be renamed. For example, the following `_simulate` call returns a parse exception:
+
+```json
+POST _ingest/pipeline/dot-expander-pipeline/_simulate
+{
+  "docs": [
+    {
+      "_index": "testindex1",
+      "_id": "1",
+      "_source": {
+        "user": "John",
+        "user.name": "Steve"
+      }
+    }
+  ]
+}
+```
+
+To avoid the parse exception, first rename the field by using the `rename` processor:
+
+```json
+PUT /_ingest/pipeline/dot-expander-pipeline
+{
+  "processors" : [
+    {
+      "rename" : {
+        "field" : "user",
+        "target_field" : "user.name"
+      }
+    },
+    {
+      "dot_expander": {
+        "field": "user.name"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+Now you can simulate the pipeline:
+
+```json
+POST _ingest/pipeline/dot-expander-pipeline/_simulate
+{
+  "docs": [
+    {
+      "_index": "testindex1",
+      "_id": "1",
+      "_source": {
+        "user": "John",
+        "user.name": "Steve"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+The response confirms that the fields were merged:
+
+```json
+{
+  "docs": [
+    {
+      "doc": {
+        "_index": "testindex1",
+        "_id": "1",
+        "_source": {
+          "user": {
+            "name": [
+              "John",
+              "Steve"
+            ]
+          }
+        },
+        "_ingest": {
+          "timestamp": "2024-01-17T01:52:12.864432419Z"
+        }
+      }
+    }
+  ]
+}
+```