Add DuckDB FlightSQL sample connector (ADBC)

samples/DuckDbFlightSQL/.vscode/settings.json

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+{
+  "powerquery.general.mode": "SDK",
+  "powerquery.sdk.test.settingsFiles": "./Tests/Settings",
+  "powerquery.sdk.defaultExtension": "${workspaceFolder}\\bin\\AnyCPU\\Debug\\DuckDb.mez",
+  "powerquery.sdk.defaultQueryFile": "${workspaceFolder}\\DuckDb.query.pq"
+}

samples/DuckDbFlightSQL/DuckDb.proj

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+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="Current" Sdk="Microsoft.Build.NoTargets/3.7.56" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <EnableLocalization>False</EnableLocalization>
+  </PropertyGroup>
+  <ItemGroup>
+    <MEZContent Include="DuckDb.pq" />
+    <MEZContent Include="FlightSqlAdbcConfig.pqm" />
+    <MEZContent Include="TypeInfo.pqm" />
+    <MEZContent Include="SqlGenerator.pqm" />
+    <MEZContent Include="SqlGeneratorCommon.pqm" />
+    <MEZContent Include="resources.resx" />
+  </ItemGroup>
+  <PropertyGroup>
+    <MezOutputDir>$(MSBuildProjectDirectory)\bin\AnyCPU\Debug\</MezOutputDir>
+    <MezStagingDir>$(MSBuildProjectDirectory)\obj\MEZ\</MezStagingDir>
+    <MezOutputPath>$(MezOutputDir)$(MSBuildProjectName).mez</MezOutputPath>
+  </PropertyGroup>
+  <Target Name="PackageMez" AfterTargets="Build" Inputs="@(MEZContent)" Outputs="$(MezOutputPath)">
+    <RemoveDir Directories="$(MezStagingDir)" />
+    <MakeDir Directories="$(MezStagingDir)" />
+    <Copy SourceFiles="@(MEZContent)" DestinationFolder="$(MezStagingDir)" />
+    <MakeDir Directories="$(MezOutputDir)" Condition="!Exists('$(MezOutputDir)')" />
+    <ZipDirectory SourceDirectory="$(MezStagingDir)" DestinationFile="$(MezOutputPath)" Overwrite="true" />
+    <Message Text="Created $(MezOutputPath)" Importance="high" />
+  </Target>
+</Project>

samples/DuckDbFlightSQL/DuckDb.query.pq

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+// Use this file to write queries to test your data connector.
+// Pressing Evaluate (or Ctrl+E) in VS Code will execute this query
+// against the extension defined in .vscode/settings.json.
+let
+    Source = DuckDb.Contents("localhost:31337", "Disabled")
+in
+    Source

samples/DuckDbFlightSQL/FlightSqlAdbcConfig.pqm

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+// FlightSqlAdbcConfig.pqm — ADBC driver configuration for DuckDb via FlightSQL.
+let
+    TypeInfo = Extension.LoadExpression("TypeInfo.pqm"),
+    FlightSqlAdbcConfig = [
+        Name = "FlightSqlAdbcDuckDb",
+        Folder = "FlightSQL",
+        File = "libadbc_driver_flightsql.dll",
+        DriverType = "Unmanaged",
+        EntryPoint = "FlightSqlDriverInit",
+        IdentifierQuoteChar = """",
+        CatalogNameSeparator = ".",
+        TableTypes = "BASE TABLE, VIEW",
+        SupportsCatalog = true,
+        SupportsSchema = true,
+        SupportedConnectionOptions = [
+            adbc.connection.catalog = false,
+            adbc.connection.db_schema = false
+        ],
+        TypeInfo = Table.SelectColumns(
+            TypeInfo,
+            {"Name", "SqlType", "Unsigned", "ColumnSize", "NumberPrecisionRadix", "LiteralPrefix", "LiteralSuffix"}
+        )
+    ],
+    Extension.LoadExpression = (name as text) =>
+        let
+            binary = Extension.Contents(name),
+            asText = Text.FromBinary(binary)
+        in
+            Expression.Evaluate(asText, #shared)
+in
+    FlightSqlAdbcConfig

samples/DuckDbFlightSQL/README.md

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+# DuckDb Connector (FlightSQL / ADBC)
+
+A sample Power Query M connector for **DuckDb** using the **FlightSQL** protocol via **ADBC** (Arrow Database Connectivity). Designed as a reference implementation for partners building FlightSQL-based connectors for Power BI.
+
+## Architecture
+
+Uses **`Adbc.Connection`** exclusively — no ODBC, `Adbc.Query`, or `Adbc.Database` needed.
+
+| Feature            | Implementation                                          |
+| ------------------ | ------------------------------------------------------- |
+| **Connection**     | `Adbc.Connection` via FlightSQL gRPC                    |
+| **Navigation**     | Database → Schema → Table via `information_schema`      |
+| **Query Folding**  | `SqlView.Generator` with DuckDb-specific `SqlGenerator` |
+| **Type Mapping**   | Full DuckDb coverage (BOOLEAN through STRUCT/MAP)       |
+| **Relationships**  | PK/FK detection via `information_schema` constraints    |
+| **Authentication** | Username/Password, Bearer Token, Anonymous              |
+| **DirectQuery**    | Supported                                               |
+| **Native Query**   | Supported with folding                                  |
+
+## FlightSQL ADBC Driver
+
+The FlightSQL ADBC driver (`libadbc_driver_flightsql.dll`) ships with both **Power Query SDK Tools** and **Power BI Desktop**. No separate driver installation is needed.
+
+`FlightSqlAdbcConfig.pqm` configures the driver by specifying:
+
+- **Driver location**: folder (`FlightSQL`), file name, and entry point (`FlightSqlDriverInit`)
+- **Metadata**: catalog/schema support, identifier quoting, supported table types (`BASE TABLE`, `VIEW`)
+- **Type mapping**: references `TypeInfo.pqm` for DuckDB-to-M type resolution
+
+The connector uses `Adbc.Connection` with `grpc://` (TLS disabled) or `grpc+tls://` (TLS enabled) URIs to establish the FlightSQL gRPC connection.
+
+## Files
+
+```text
+DuckDb/
+├── DuckDb.pq                    # Main connector entry point
+├── DuckDb.query.pq              # Evaluation query for SDK testing
+├── FlightSqlAdbcConfig.pqm      # ADBC driver configuration
+├── TypeInfo.pqm                 # DuckDb type → M type mapping
+├── SqlGenerator.pqm             # DuckDb SQL generator overrides
+├── SqlGeneratorCommon.pqm       # Shared Sql92 base infrastructure
+├── DuckDb.proj                  # Power Query SDK project file
+├── resources.resx               # Localized strings
+└── Tests/
+    ├── Credentials/             # Credential files for test authentication
+    ├── ParameterQueries/        # Parameter query definitions
+    ├── Settings/                # PQTest settings (Sanity, Standard, DatasourceSpecific)
+    ├── TestSuites/              # Test cases organized by category
+    │   ├── Setup/               # Docker setup, data loading, readme
+    │   ├── DatasourceSpecific/  # DuckDB-specific tests
+    │   └── PerfTests/           # Performance test queries
+    │   # Sanity & Standard tests use shared testframework/tests/TestSuites/
+    ├── RunDuckDbTestsWithVSCodeGuide.md   # VS Code test guide
+    └── RunDuckDbPerfTestsGuide.md         # Performance test guide
+```
+
+## Key Design Decisions
+
+### Adbc.Connection Only
+
+Simplest approach for FlightSQL — directly creates a connection, builds navigation via SQL metadata queries, and wires up `SqlView.Generator` for folding.
+
+### SQL Generator
+
+The query folding engine uses a three-layer override architecture:
+
+| Layer                | File                     | Role                                                                                              |
+| -------------------- | ------------------------ | ------------------------------------------------------------------------------------------------- |
+| **SQL92 Base**       | `SqlGeneratorCommon.pqm` | Shared infrastructure: type validation, AST helpers, 40+ function stubs, base SQL92 capabilities  |
+| **DuckDB Overrides** | `SqlGenerator.pqm`       | DuckDB dialect: 24 type facets, LIMIT/OFFSET syntax, function remapping, typed literal generation |
+| **Connector Wiring** | `DuckDb.pq`              | Creates `SqlView.Generator` instance, wires to `Adbc.Connection` via `GetData`                    |
+
+`SqlGenerator.pqm` loads the base via `Extension.LoadExpression()`, defines an override record, and calls `MergeOverrides("Sql92", Override, false)` to produce the final generator.
+
+**Key DuckDB overrides:**
+
+- **LIMIT/OFFSET**: Translates M's `Table.FirstN`/`Table.Skip` to `LIMIT n OFFSET m`
+- **Function remapping**: `TIMESTAMPADD`/`TIMESTAMPDIFF` to DuckDB's `date_add`/`date_diff`, `Text.PositionOf` to `INSTR`, `Text.StartsWith` to `starts_with`
+- **Typed literals**: `DATE '2023-01-01'`, `TIMESTAMP '...'`, `TIME '...'`, `CAST(value AS TYPE)` for numeric/string types
+- **Type facets**: 24 DuckDB types with `NativeTypeName`, precision, radix, and scale metadata
+- **Supported conversions**: Type casting rules (e.g., `BOOLEAN` to `VARCHAR`/`DECIMAL`/`BIGINT`)
+
+Partners building new ADBC connectors can use this as a template: copy `SqlGeneratorCommon.pqm` as-is, then create a dialect-specific `SqlGenerator.pqm` with overrides for their database's SQL syntax and type system.
+
+### Primary & Foreign Keys
+
+Queries `information_schema.table_constraints` + `key_column_usage` for PKs, applies them via `Type.ReplaceTableKeys`. Exposes `GetForeignKeys()` for FK discovery. Power BI uses these to auto-create relationships.
+
+## Supported Types
+
+BOOLEAN, TINYINT, SMALLINT, INTEGER, BIGINT, HUGEINT, FLOAT, DOUBLE, DECIMAL, DATE, TIME, TIMESTAMP, TIMESTAMP WITH TIME ZONE, VARCHAR, CHAR, BLOB, BINARY, UUID, JSON, INTERVAL, ARRAY, STRUCT, MAP
+
+## Testing
+
+Tests require a DuckDB FlightSQL server running locally. See [Test Data Setup](Tests/TestSuites/Setup/readme.md) for Docker container setup and data loading instructions.
+
+- [Running Tests with VS Code](Tests/RunDuckDbTestsWithVSCodeGuide.md) — recommended approach using Test Explorer
+- [Running Performance Tests](Tests/RunDuckDbPerfTestsGuide.md) — performance testing with PQPerf
+
+## Building
+
+```powershell
+dotnet build DuckDb.proj
+```