[Backport 2.18] add simple analyzer docs

_analyzers/simple.md

@@ -0,0 +1,98 @@
+---
+layout: default
+title: Simple analyzer
+nav_order: 50
+---
+
+# Simple analyzer
+
+The `simple` analyzer is a very basic analyzer that breaks text into terms at non-letter characters and lowercases the terms. Unlike the `standard` analyzer, the `simple` analyzer treats everything except for alphabetic characters as delimiters, meaning that it does not recognize numbers, punctuation, or special characters as part of the tokens.
+
+## Example 
+
+Use the following command to create an index named `my_simple_index` with a `simple` analyzer:
+
+```json
+PUT /my_simple_index
+{
+  "mappings": {
+    "properties": {
+      "my_field": {
+        "type": "text",
+        "analyzer": "simple"
+      }
+    }
+  }
+}
+```
+{% 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 `simple` analyzer with an added `html_strip` character filter:
+
+```json
+PUT /my_custom_simple_index
+{
+  "settings": {
+    "analysis": {
+      "char_filter": {
+        "html_strip": {
+          "type": "html_strip"
+        }
+      },
+      "tokenizer": {
+        "my_lowercase_tokenizer": {
+          "type": "lowercase"
+        }
+      },
+      "analyzer": {
+        "my_custom_simple_analyzer": {
+          "type": "custom",
+          "char_filter": ["html_strip"],
+          "tokenizer": "my_lowercase_tokenizer",
+          "filter": ["lowercase"]
+        }
+      }
+    }
+  },
+  "mappings": {
+    "properties": {
+      "my_field": {
+        "type": "text",
+        "analyzer": "my_custom_simple_analyzer"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST /my_custom_simple_index/_analyze
+{
+  "analyzer": "my_custom_simple_analyzer",
+  "text": "<p>The slow turtle swims over to dogs &copy; 2024!</p>"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {"token": "the","start_offset": 3,"end_offset": 6,"type": "word","position": 0},
+    {"token": "slow","start_offset": 7,"end_offset": 11,"type": "word","position": 1},
+    {"token": "turtle","start_offset": 12,"end_offset": 18,"type": "word","position": 2},
+    {"token": "swims","start_offset": 19,"end_offset": 24,"type": "word","position": 3},
+    {"token": "over","start_offset": 25,"end_offset": 29,"type": "word","position": 4},
+    {"token": "to","start_offset": 30,"end_offset": 32,"type": "word","position": 5},
+    {"token": "dogs","start_offset": 33,"end_offset": 37,"type": "word","position": 6}
+  ]
+}
+```