add lowercase tokenizer docs (#8497) (#8910)

* add lowercase tokenizer docs * Doc review * Apply suggestions from code review --------- (cherry picked from commit 68a8af5) Signed-off-by: Anton Rubin <[email protected]> Signed-off-by: Fanit Kolchina <[email protected]> Signed-off-by: kolchfa-aws <[email protected]> Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com> Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com> Co-authored-by: Fanit Kolchina <[email protected]> Co-authored-by: kolchfa-aws <[email protected]> Co-authored-by: Nathan Bower <[email protected]>
opensearch-project · Dec 9, 2024 · d8f6190 · d8f6190
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diff --git a/_analyzers/tokenizers/lowercase.md b/_analyzers/tokenizers/lowercase.md
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+---
+layout: default
+title: Lowercase
+parent: Tokenizers
+nav_order: 70
+---
+
+# Lowercase tokenizer
+
+The `lowercase` tokenizer breaks text into terms at white space and then lowercases all the terms. Functionally, this is identical to configuring a `letter` tokenizer with a `lowercase` token filter. However, using a `lowercase` tokenizer is more efficient because the tokenizer actions are performed in a single step.
+
+## Example usage
+
+The following example request creates a new index named `my-lowercase-index` and configures an analyzer with a `lowercase` tokenizer:
+
+```json
+PUT /my-lowercase-index
+{
+  "settings": {
+    "analysis": {
+      "tokenizer": {
+        "my_lowercase_tokenizer": {
+          "type": "lowercase"
+        }
+      },
+      "analyzer": {
+        "my_lowercase_analyzer": {
+          "type": "custom",
+          "tokenizer": "my_lowercase_tokenizer"
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST /my-lowercase-index/_analyze
+{
+  "analyzer": "my_lowercase_analyzer",
+  "text": "This is a Test. OpenSearch 123!"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "this",
+      "start_offset": 0,
+      "end_offset": 4,
+      "type": "word",
+      "position": 0
+    },
+    {
+      "token": "is",
+      "start_offset": 5,
+      "end_offset": 7,
+      "type": "word",
+      "position": 1
+    },
+    {
+      "token": "a",
+      "start_offset": 8,
+      "end_offset": 9,
+      "type": "word",
+      "position": 2
+    },
+    {
+      "token": "test",
+      "start_offset": 10,
+      "end_offset": 14,
+      "type": "word",
+      "position": 3
+    },
+    {
+      "token": "opensearch",
+      "start_offset": 16,
+      "end_offset": 26,
+      "type": "word",
+      "position": 4
+    }
+  ]
+}
+```