[DOCS] Update ESQL metadata fields page (#129939)

* [DOCS] Update ESQL metadata fields page

**esql-metadata-fields.md:**
- restructured from bullet list to table format for metadata fields
- added `_index_mode` and `_source` fields to available metadata
- improved field descriptions (more detailed)
- added "usage and limitations" section
- reorganized examples into subsections with headers
- added `_score` sorting example
- added tip box linking to search documentation

* 🚙Drive by updates to search functions ref page

moved tutorial link into tip box at top
added cross-reference to search overview documentation
minor text flow improvements and punctuation fixes

* Fix id typo

* Apply suggestions from review

Co-authored-by: Bogdan Pintea <[email protected]>

Author: leemthompo

docs/reference/query-languages/esql/esql-metadata-fields.md

@@ -6,24 +6,40 @@ mapped_pages:
 
 # {{esql}} metadata fields [esql-metadata-fields]
 
+{{esql}} can access [metadata fields](/reference/elasticsearch/mapping-reference/document-metadata-fields.md).
 
-{{esql}} can access [metadata fields](/reference/elasticsearch/mapping-reference/document-metadata-fields.md). The currently supported ones are:
-
-* [`_index`](/reference/elasticsearch/mapping-reference/mapping-index-field.md): the index to which the document belongs. The field is of the type [keyword](/reference/elasticsearch/mapping-reference/keyword.md).
-* [`_id`](/reference/elasticsearch/mapping-reference/mapping-id-field.md): the source document’s ID. The field is of the type [keyword](/reference/elasticsearch/mapping-reference/keyword.md).
-* `_version`: the source document’s version. The field is of the type [long](/reference/elasticsearch/mapping-reference/number.md).
-* [`_ignored`](/reference/elasticsearch/mapping-reference/mapping-ignored-field.md): the ignored source document fields. The field is of the type [keyword](/reference/elasticsearch/mapping-reference/keyword.md).
-* `_score`: when enabled, the final score assigned to each row matching an ES|QL query. Scoring will be updated when using [full text search functions](/reference/query-languages/esql/functions-operators/search-functions.md).
-
-To enable the access to these fields, the [`FROM`](/reference/query-languages/esql/commands/source-commands.md#esql-from) source command needs to be provided with a dedicated directive:
+To access these fields, use the `METADATA` directive with the [`FROM`](/reference/query-languages/esql/commands/source-commands.md#esql-from) source command. For example:
 
 ```esql
 FROM index METADATA _index, _id
 ```
 
-Metadata fields are only available if the source of the data is an index. Consequently, `FROM` is the only source commands that supports the `METADATA` directive.
+## Available metadata fields
+
+The following metadata fields are available in {{esql}}:
+
+| Metadata field | Type | Description |
+|---------------|------|-------------|
+| [`_id`](/reference/elasticsearch/mapping-reference/mapping-id-field.md) | [keyword](/reference/elasticsearch/mapping-reference/keyword.md) | Unique document ID. |
+| [`_ignored`](/reference/elasticsearch/mapping-reference/mapping-ignored-field.md) | [keyword](/reference/elasticsearch/mapping-reference/keyword.md) | Names every field in a document that was ignored when the document was indexed. |
+| [`_index`](/reference/elasticsearch/mapping-reference/mapping-index-field.md) | [keyword](/reference/elasticsearch/mapping-reference/keyword.md) | Index name. |
+| `_index_mode` | [keyword](/reference/elasticsearch/mapping-reference/keyword.md) | [Index mode](/reference/elasticsearch/index-settings/index-modules.md#index-mode-setting). For example: `standard`, `lookup`, or `logsdb`. |
+| `_score` | [`float`](/reference/elasticsearch/mapping-reference/number.md) | Query relevance score (when enabled). Scores are updated when using [full text search functions](/reference/query-languages/esql/functions-operators/search-functions.md). |
+| [`_source`](/reference/elasticsearch/mapping-reference/mapping-source-field.md) | Special `_source` type | Original JSON document body passed at index time (or a reconstructed version if [synthetic `_source`](/reference/elasticsearch/mapping-reference/mapping-source-field.md#synthetic-source) is enabled). |
+| `_version` | [`long`](/reference/elasticsearch/mapping-reference/number.md) | Document version number |
+
+## Usage and limitations
+
+- Metadata fields are only available when the data source is an index
+- The `_source` type is not supported by functions
+- Only the `FROM` command supports the `METADATA` directive
+- Once enabled, metadata fields work like regular index fields
+
+## Examples
 
-Once enabled, these fields will be available to subsequent processing commands, just like other index fields:
+### Basic metadata usage
+
+Once enabled, metadata fields are available to subsequent processing commands, just like other index fields:
 
 ```esql
 FROM ul_logs, apps METADATA _index, _version
@@ -40,6 +56,8 @@ FROM ul_logs, apps METADATA _index, _version
 | 14 | apps | 1 | apps_14 |
 | 14 | ul_logs | 1 | ul_logs_14 |
 
+### Metadata fields and aggregations
+
 Similar to index fields, once an aggregation is performed, a metadata field will no longer be accessible to subsequent commands, unless used as a grouping field:
 
 ```esql
@@ -51,3 +69,15 @@ FROM employees METADATA _index, _id
 | --- | --- |
 | 10100 | employees |
 
+### Sort results by search score
+
+```esql
+FROM products METADATA _score
+| WHERE MATCH(description, "wireless headphones")
+| SORT _score DESC
+| KEEP name, description, _score
+```
+
+:::{tip}
+Refer to [{{esql}} for search](docs-content://solutions/search/esql-for-search.md#esql-for-search-scoring) for more information on relevance scoring and how to use `_score` in your queries.
+:::

docs/reference/query-languages/esql/functions-operators/search-functions.md

@@ -6,21 +6,27 @@ mapped_pages:
 
 # {{esql}} Search functions [esql-search-functions]
 
+:::{tip}
+Get started with {{esql}} for search use cases with
+our [hands-on tutorial](docs-content://solutions/search/esql-search-tutorial.md).
+
+For a high-level overview of search functionalities in {{esql}}, and to learn about relevance scoring, refer to [{{esql}} for search](docs-content://solutions/search/esql-for-search.md#esql-for-search-scoring).
+:::
+
+{{esql}} provides a set of functions for performing searching on text fields. 
+
 Use these functions
 for [full-text search](docs-content://solutions/search/full-text.md)
 and [semantic search](docs-content://solutions/search/semantic-search/semantic-search-semantic-text.md).
 
-Get started with {{esql}} for search use cases with
-our [hands-on tutorial](docs-content://solutions/search/esql-search-tutorial.md).
-
 Full text functions can be used to
 match [multivalued fields](/reference/query-languages/esql/esql-multivalued-fields.md).
 A multivalued field that contains a value that matches a full text query is
 considered to match the query.
 
 Full text functions are significantly more performant for text search use cases
 on large data sets than using pattern matching or regular expressions with
-`LIKE` or `RLIKE`
+`LIKE` or `RLIKE`.
 
 See [full text search limitations](/reference/query-languages/esql/limitations.md#esql-limitations-full-text-search)
 for information on the limitations of full text search.