Add docs for Loki connector

docs/src/main/sphinx/connector.md

@@ -25,6 +25,7 @@ Ignite          <connector/ignite>
 JMX             <connector/jmx>
 Kafka           <connector/kafka>
 Kudu            <connector/kudu>
+Loki            <connector/loki>
 MariaDB         <connector/mariadb>
 Memory          <connector/memory>
 MongoDB         <connector/mongodb>

docs/src/main/sphinx/connector/loki.md

@@ -0,0 +1,71 @@
+# Loki connector
+
+```{raw} html
+<img src="../_static/img/loki.png" class="connector-logo">
+```
+
+The Loki connector allows querying log data stored in [Grafana
+Loki](https://grafana.com/oss/loki/). This document describes how to configure a
+catalog with the Loki connector to run SQL queries against Loki.
+
+## Requirements
+
+To connect to Loki, you need:
+
+- Loki 3.1.0 or higher.
+- Network access from the Trino coordinator and workers to Loki.
+  Port 3100 is the default port.
+
+## Configuration
+
+The connector can query log data in Loki. Create a catalog properties file that
+specifies the Loki connector by setting the `connector.name` to `loki`.
+
+For example, to access a database as the `example` catalog, create the file
+`etc/catalog/example.properties`.
+
+```text
+connector.name=loki
+loki.uri=http://loki.example.com:3100
+```
+
+The `loki.uri` property specifies the URI endpoint for the Loki server that
+Trino cluster nodes use to access the Loki APIs.
+
+The optional property `loki.query-timeout` defaults to `10s` and controls the
+[duration]() Trino waits for a result from Loki before the specific query
+request times out. A minimum of `1s` is required.
+
+(loki-type-mapping)=
+## Type mapping
+
+Because Trino and Loki each support types that the other does not, this
+connector [modifies some types](type-mapping-overview) when reading data.
+
+### Loki type to Trino type mapping
+
+The connector maps Loki types to the corresponding Trino types following
+this table:
+
+:::{list-table} Loki type to Trino type mapping
+:widths: 40, 60
+:header-rows: 1
+
+* - Loki type
+  - Trino type
+* - `tbd`
+  - `tbd`
+:::
+
+No other types are supported.
+
+(loki-sql-support)=
+## SQL support
+
+The connector provides read access to data and metadata in Loki. In addition to
+the [globally available](sql-globally-available) and [read
+operation](sql-read-operations) statements, the connector supports the following
+features:
+
+(loki-query-function)=
+#### `query_range(varchar) -> table`