Add Databricks dialect documentation (#291)

- New dialect page with connection config, table references, limitations, functions
- Add Databricks connection parameters to config.malloynb
- Add Databricks to database support page, sidebar, and connections page

Author: mtoy-googly-moogly

src/documentation/language/connections.malloynb

@@ -25,6 +25,10 @@ In the official Malloy connection implementations, the behavior is as follows:
 
 In BigQuery, the string passed to the `.table()` connection method can be a two- or three-segment path including the (optional) project ID, dataset ID, and table name, e.g. `bigquery.table('project-id.dataset-id.table-name')` or `bigquery.table('dataset-id.table-name')`. If the project ID is left off, the default project ID for the connection will be used, or else the system default if none is set on the connection.
 
+### Databricks
+
+In Databricks, the string passed to the `.table()` connection method can be a one-, two-, or three-segment path: `table`, `schema.table`, or `catalog.schema.table`. If the catalog or schema is omitted, the configured defaults (or workspace defaults) are used.
+
 ### DuckDB
 
 In DuckDB, the `.table()` method accepts the path (relative to the Malloy file) of CSV, JSON, or Parquet file containing the table data, e.g. `duckdb.table('data/users.csv')` or `duckdb.table('../../users.parquet')`. URLs to such files (or APIs) are also allowed: see [an example here](../patterns/apijson.malloynb).

src/documentation/language/dialect/databricks.malloynb

@@ -0,0 +1,67 @@
+>>>markdown
+# Databricks
+
+Databricks uses the [Databricks SQL Connector](https://docs.databricks.com/en/dev-tools/nodejs-sql-driver.html) to connect to Databricks SQL warehouses and clusters.
+
+## Connection Configuration
+
+In `malloy-config.json`:
+
+```json
+{
+  "connections": {
+    "databricks": {
+      "is": "databricks",
+      "host": "my-workspace.cloud.databricks.com",
+      "path": "/sql/1.0/warehouses/abc123",
+      "token": {"env": "DATABRICKS_TOKEN"}
+    }
+  }
+}
+```
+
+| Parameter | Type | Description |
+|---|---|---|
+| `host` | string | Databricks workspace hostname (e.g. `my-workspace.cloud.databricks.com`) |
+| `path` | string | SQL warehouse HTTP path (e.g. `/sql/1.0/warehouses/abc123`) |
+| `token` | secret | Personal access token (optional if using OAuth) |
+| `oauthClientId` | string | OAuth M2M client ID (optional) |
+| `oauthClientSecret` | secret | OAuth M2M client secret (optional) |
+| `defaultCatalog` | string | Default Unity Catalog name (optional) |
+| `defaultSchema` | string | Default schema name (optional) |
+| `setupSQL` | text | Connection setup SQL ([see configuration docs](../../setup/config.malloynb#setup-sql)) |
+
+Authentication is either **personal access token** (`token`) or **OAuth M2M** (`oauthClientId` + `oauthClientSecret`).
+
+## Table References
+
+The `.table()` method accepts a one-, two-, or three-segment path: `table`, `schema.table`, or `catalog.schema.table`. If the catalog or schema is omitted, the configured defaults (or workspace defaults) are used.
+
+```malloy
+source: flights is databricks.table('malloytest.flights')
+source: orders is databricks.table('my_catalog.analytics.orders')
+```
+
+## Limitations
+
+- **`string_agg` ordering**: Databricks does not support `ORDER BY` inside `COLLECT_LIST`/`COLLECT_SET`, so `string_agg` and `string_agg_distinct` do not support the `order_by` modifier.
+- **`TIMESTAMP_NTZ`**: Databricks' `TIMESTAMP_NTZ` (timestamp without timezone) maps to `sql native` in Malloy. Use explicit casting to `timestamp` when needed.
+
+# Functions
+
+## Useful Functions not in the database function library
+
+    string_agg_distinct
+
+## Database Functions
+
+Malloy code can, in addition to the [Malloy Standard Functions](../functions.malloynb), reference
+any of the listed functions here without needing to use [Raw SQL Functions](../functions.malloynb#raw-sql-functions).
+
+    string_agg
+    repeat
+    reverse
+
+# External Resources
+
+* [Databricks SQL Reference](https://docs.databricks.com/en/sql/language-manual/index.html)

src/documentation/setup/config.malloynb

@@ -58,6 +58,21 @@ The `is` field identifies the connection type. All other fields are type-specifi
 | `billingProjectId` | string | Billing project (if different) |
 | `setupSQL` | text | Connection setup SQL ([see below](#setup-sql)) |
 
+### `databricks` — Databricks
+
+| Parameter | Type | Description |
+|---|---|---|
+| `host` | string | Workspace hostname (e.g. `my-workspace.cloud.databricks.com`) |
+| `path` | string | SQL warehouse HTTP path (e.g. `/sql/1.0/warehouses/abc123`) |
+| `token` | secret | Personal access token (optional if using OAuth) |
+| `oauthClientId` | string | OAuth M2M client ID |
+| `oauthClientSecret` | secret | OAuth M2M client secret |
+| `defaultCatalog` | string | Default Unity Catalog name |
+| `defaultSchema` | string | Default schema name |
+| `setupSQL` | text | Connection setup SQL ([see below](#setup-sql)) |
+
+Authentication: provide either `token` or the `oauthClientId` + `oauthClientSecret` pair.
+
 ### `postgres` — PostgreSQL
 
 | Parameter | Type | Description |

src/documentation/setup/database_support.malloynb

@@ -10,6 +10,7 @@ Malloy connects to a variety of databases. This page provides an overview of sup
 | [DuckDB](../language/dialect/duckdb.malloynb) | `duckdb` | Built-in, no setup required. Reads Parquet, CSV, JSON files |
 | [MotherDuck](../language/dialect/duckdb.malloynb) | `duckdb` | Cloud-hosted DuckDB |
 | [BigQuery](../language/dialect/bigquery.malloynb) | `bigquery` | OAuth or service account authentication |
+| [Databricks](../language/dialect/databricks.malloynb) | `databricks` | Personal access token or OAuth M2M |
 | [Snowflake](../language/dialect/snowflake.malloynb) | `snowflake` | Password or RSA key authentication |
 | [PostgreSQL](../language/dialect/postgres.malloynb) | `postgres` | Standard credentials |
 | [MySQL](../language/dialect/mysql.malloynb) | `mysql` | Standard credentials |
@@ -74,6 +75,7 @@ Each database supports [Malloy Standard Functions](../language/functions.malloyn
 |----------|-------------------|
 | DuckDB | [DuckDB Functions](https://duckdb.org/docs/sql/functions/overview) |
 | BigQuery | [BigQuery Functions](https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators) |
+| Databricks | [Databricks Functions](https://docs.databricks.com/en/sql/language-manual/sql-ref-functions-builtin.html) |
 | Snowflake | [Snowflake Functions](https://docs.snowflake.com/en/sql-reference-functions) |
 | PostgreSQL | [PostgreSQL Functions](https://www.postgresql.org/docs/current/functions.html) |
 | MySQL | [MySQL Functions](https://dev.mysql.com/doc/refman/8.0/en/functions.html) |
@@ -90,6 +92,7 @@ Each database has unique capabilities and limitations. See the dialect documenta
 
 - [DuckDB](../language/dialect/duckdb.malloynb) - File-based queries, approximate counts, full bigint precision
 - [BigQuery](../language/dialect/bigquery.malloynb) - HyperLogLog, approximate counts, full bigint precision
+- [Databricks](../language/dialect/databricks.malloynb) - Unity Catalog, SQL warehouses, full bigint precision
 - [Snowflake](../language/dialect/snowflake.malloynb) - HyperLogLog, TOML credential file support, full bigint precision
 - [PostgreSQL](../language/dialect/postgres.malloynb) - String aggregation extensions, limited bigint precision
 - [MySQL](../language/dialect/mysql.malloynb) - Boolean type workarounds, full bigint precision

src/table_of_contents.json

@@ -218,6 +218,10 @@
               "title": "BigQuery",
               "link": "/language/dialect/bigquery.malloynb"
             },
+            {
+              "title": "Databricks",
+              "link": "/language/dialect/databricks.malloynb"
+            },
             {
               "title": "Presto / Trino",
               "link": "/language/dialect/presto-trino.malloynb"