[Backport 2.18] add whitespace analyzer docs

_analyzers/whitespace.md

@@ -0,0 +1,86 @@
+---
+layout: default
+title: Whitespace analyzer
+nav_order: 60
+---
+
+# Whitespace analyzer
+
+The `whitespace` analyzer breaks text into tokens based only on white space characters (for example, spaces and tabs). It does not apply any transformations, such as lowercasing or removing stopwords, so the original case of the text is retained and punctuation is included as part of the tokens.
+
+## Example
+
+Use the following command to create an index named `my_whitespace_index` with a `whitespace` analyzer:
+
+```json
+PUT /my_whitespace_index
+{
+  "mappings": {
+    "properties": {
+      "my_field": {
+        "type": "text",
+        "analyzer": "whitespace"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Configuring a custom analyzer
+
+Use the following command to configure an index with a custom analyzer that is equivalent to a `whitespace` analyzer with an added `lowercase` character filter:
+
+```json
+PUT /my_custom_whitespace_index
+{
+  "settings": {
+    "analysis": {
+      "analyzer": {
+        "my_custom_whitespace_analyzer": {
+          "type": "custom",
+          "tokenizer": "whitespace",
+          "filter": ["lowercase"]
+        }
+      }
+    }
+  },
+  "mappings": {
+    "properties": {
+      "my_field": {
+        "type": "text",
+        "analyzer": "my_custom_whitespace_analyzer"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST /my_custom_whitespace_index/_analyze
+{
+  "analyzer": "my_custom_whitespace_analyzer",
+  "text": "The SLOW turtle swims away! 123"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {"token": "the","start_offset": 0,"end_offset": 3,"type": "word","position": 0},
+    {"token": "slow","start_offset": 4,"end_offset": 8,"type": "word","position": 1},
+    {"token": "turtle","start_offset": 9,"end_offset": 15,"type": "word","position": 2},
+    {"token": "swims","start_offset": 16,"end_offset": 21,"type": "word","position": 3},
+    {"token": "away!","start_offset": 22,"end_offset": 27,"type": "word","position": 4},
+    {"token": "123","start_offset": 28,"end_offset": 31,"type": "word","position": 5}
+  ]
+}
+```