[Backport 2.14] [DOC] Add trim processor documentation

_ingest-pipelines/processors/trim.md

@@ -0,0 +1,165 @@
+---
+layout: default
+title: Trim
+parent: Ingest processors
+nav_order: 300
+---
+
+# Trim processor
+
+The `trim` processor is used to remove leading and trailing white space characters from a specified field.
+
+The following is the syntax for the `trim` processor:
+
+```json
+{
+  "trim": {
+    "field": "field_to_trim",
+    "target_field": "trimmed_field"
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Configuration parameters
+
+The following table lists the required and optional parameters for the `trim` processor.
+
+Parameter | Required/Optional | Description |
+|-----------|-----------|-----------|
+`field` | Required | The field containing the text to be trimmed.
+`target_field` | Required | The field in which the trimmed text is stored. If not specified, then the field is updated in-place.
+`ignore_missing` | Optional | Specifies whether the processor should ignore documents that do not contain the specified 
+field. If set to `true`, then the processor ignores missing values in the field and leaves the `target_field` unchanged. Default is `false`.
+`description` | Optional | A brief description of the processor.
+`if` | Optional | A condition for running the processor.
+`ignore_failure` | Optional | Specifies whether the processor continues execution even if it encounters an error. If set to `true`, then 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 pipeline named `trim_pipeline` that uses the `trim` processor to remove leading and trailing white space from the `raw_text` field and store the trimmed text in the `trimmed_text` field: 
+
+```json
+PUT _ingest/pipeline/trim_pipeline
+{
+  "description": "Trim leading and trailing white space",
+  "processors": [
+    {
+      "trim": {
+        "field": "raw_text",
+        "target_field": "trimmed_text"
+      }
+    }
+  ]
+}
+```
+{% 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/trim_pipeline/_simulate
+{
+  "docs": [
+    {
+      "_source": {
+        "raw_text": "   Hello, world!   "
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The following example response confirms that the pipeline is working as expected:
+
+```json
+{
+  "docs": [
+    {
+      "doc": {
+        "_index": "_index",
+        "_id": "_id",
+        "_source": {
+          "raw_text": "   Hello, world!   ",
+          "trimmed_text": "Hello, world!"
+        },
+        "_ingest": {
+          "timestamp": "2024-04-26T20:58:17.418006805Z"
+        }
+      }
+    }
+  ]
+}
+```
+
+### Step 3: Ingest a document 
+
+The following query ingests a document into an index named `testindex1`:
+
+```json
+PUT testindex1/_doc/1?pipeline=trim_pipeline
+{
+  "message": "   This is a test document.   "
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The request indexes the document into the index `testindex1` and indexes all documents with the `raw_text` field, which is processed by the `trim_pipeline`, to populate the `trimmed_text` field, as shown in the following response:
+
+```json
+  "_index": "testindex1",
+  "_id": "1",
+  "_version": 68,
+  "result": "updated",
+  "_shards": {
+    "total": 2,
+    "successful": 1,
+    "failed": 0
+  },
+  "_seq_no": 70,
+  "_primary_term": 47
+}
+```
+{% 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 %}
+
+The response includes the `trimmed_text` field with the leading and trailing white space removed:
+
+```json
+{
+  "_index": "testindex1",
+  "_id": "1",
+  "_version": 69,
+  "_seq_no": 71,
+  "_primary_term": 47,
+  "found": true,
+  "_source": {
+    "raw_text": "   This is a test document.   ",
+    "trimmed_text": "This is a test document."
+  }
+}
+```