Add remove_by_pattern ingest processor

_ingest-pipelines/processors/remove_by_pattern.md

@@ -0,0 +1,133 @@
+---
+layout: default
+title: Remove_by_pattern
+parent: Ingest processors
+nav_order: 225
+redirect_from:
+   - /api-reference/ingest-apis/processors/remove_by_pattern/
+---
+
+# Remove processor
+
+The `remove_by_pattern` processor is used to remove the root level fields from a document by the specified wildcard patterns. 
+
+## Syntax
+
+The following is the syntax for the `remove_by_pattern` processor: 
+
+```json
+{
+    "remove_by_pattern": {
+        "field_pattern": "field_name_prefix*"
+    }
+}
+```
+{% include copy-curl.html %}
+
+## Configuration parameters
+
+The following table lists the required and optional parameters for the `remove_by_pattern` processor.
+
+| Parameter  | Required/Optional  | Description  |
+|---|---|---|
+`field_pattern`  | Optional  | The fields match this pattern will be removed. All of the metadata fields like `_index`, `_version`, `_version_type`, and `_id` are ignored if they match the pattern. This option only supports the root level fields in the document. |
+`exclude_field_pattern`  | Optional  | The fields do not match this pattern will be removed. All of the metadata fields like `_index`, `_version`, `_version_type`, and `_id` are ignored if they don't match the pattern. This option only supports the root level fields in the document. The `field_pattern` and `exclude_field_pattern` options are mutually exclusive. |
+`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 errors. 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 pipeline, named `remove_fields_by_pattern`, that removes the fields which match the pattern `foo*` from a document: 
+
+```json
+PUT /_ingest/pipeline/remove_fields_by_pattern
+{
+  "description": "Pipeline that removes the fields by patterns.",
+  "processors": [
+    {
+      "remove_by_pattern": {
+        "field_pattern": "foo*"
+      }
+    }
+  ]
+}
+```
+{% 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/remove_fields_by_pattern/_simulate
+{
+  "docs": [
+    {
+      "_index": "testindex1",
+      "_id": "1",
+      "_source":{
+         "foo1": "foo1",
+         "foo2": "foo2",
+         "bar": "bar"
+      }
+    }
+  ]
+}
+```
+{% 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": {
+          "bar": "bar"
+        },
+        "_ingest": {
+          "timestamp": "2023-08-24T18:02:13.218986756Z"
+        }
+      }
+    }
+  ]
+}
+```
+
+**Step 3: Ingest a document**
+
+The following query ingests a document into an index named `testindex1`:
+
+```json
+PPUT testindex1/_doc/1?pipeline=remove_fields_by_pattern
+{
+  "foo1": "foo1",
+  "foo2": "foo2",
+  "bar": "bar"
+}
+```
+{% 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 %}