DuckDB Sources

cargo install martin --locked --features=unstable-duckdb

Martin can serve vector tiles on the fly from GeoParquet files via DuckDB. Instead of incurring the overhead of serving them directly, we serve them as vector tiles.

DuckDB sources are only available via the configuration file. There is no CLI shorthand. Create a configuration file and start Martin with martin --config config.yaml. Once a DuckDB configuration exists, martin --config config.yaml --save-config resolved-config.yaml writes a copy with the resolved per-source defaults.

Run Martin with configuration file

# DuckDB / GeoParquet sources (requires --features=unstable-duckdb)
duckdb:
  # Connection pool size used by DuckDB sources unless overridden per-source. [default: 4]
  pool_size: 4
  # Optional DuckDB execution thread count for each connection.
  threads: 2
  # Optional DuckDB memory limit in megabytes for each connection.
  memory_limit_mb: 1024
  # Specify how bounds should be computed [default: quick]
  #
  # Options:
  # - `calc` compute geometry bounds on startup.
  # - `quick` same as 'calc', but the calculation will be aborted after 5 seconds.
  # - `skip` does not compute geometry bounds on startup.
  auto_bounds: quick
  sources:
    # Local GeoParquet file, published as source id `buildings`
    - geoparquet: /data/buildings.parquet
      layer_id: buildings
      geometry_column: geom
      srid: 4326
      minzoom: 0
      maxzoom: 14
      extent: 4096
      buffer: 64
      clip_geom: true
    # Remote GeoParquet over HTTP(S)
    - geoparquet: https://example.org/data/places.parquet
      layer_id: places
    # Remote GeoParquet in an object store, optionally a glob over many part files
    - geoparquet: s3://overturemaps-us-west-2/release/2026-08-19.0/theme=places/type=place/*.parquet
      layer_id: overture_places
      geometry_column: geometry
      srid: 4326

The top-level pool_size, threads, memory_limit_mb, and auto_bounds apply to every DuckDB source unless overridden on that source:

• pool_size - connection pool size per source (defaults to 4)
• threads - DuckDB thread count per connection. When unset, DuckDB uses its own default.
• memory_limit_mb - DuckDB memory limit in megabytes per connection.
• auto_bounds - how TileJSON bounds are computed (defaults to quick):
• quick - compute geometry bounds, but abort if it takes longer than 5 seconds
• calc - compute geometry bounds. The startup time may be significant.
• skip - do not compute bounds. TileJSON will omit bounds.

Each GeoParquet source supports:

• geoparquet
• a remote URL of the GeoParquet file (http, https, s3, gs, gcs, r2, az, azure, abfss and hf URLs). A remote URL may be a glob such as s3://bucket/prefix/*.parquet, which DuckDB expands into every matching part file.
• a local path or file:// URLs. Local paths must name a single file.
• layer_id - MVT source-layer and the base for the source id (defaults to the file or URL stem).
• geometry_column - geometry column name. Auto-detected when the file has exactly one geometry column.
• id_column - optional table column to use as the MVT feature id.
• srid - source SRID. Auto-detected via ST_CRS when omitted. Non-positive values are treated as unset.
• minzoom / maxzoom - optional zoom range advertised in TileJSON.
• extent - side length of the MVT tile coordinate grid each tile is encoded into (defaults to 4096, the value MapLibre assumes). Must be non-zero.
• buffer - clip margin kept around each tile edge, in tile units (defaults to 64). Increase it if you see seam artifacts on line caps/joins or polygon outlines near tile edges.
• clip_geom - controls if geometries should be clipped or encoded as is (defaults to true).

Per-source pool_size, threads, memory_limit_mb, and auto_bounds override the top-level values for that source.

Database sources

A database: entry names a DuckDB database file. The configuration parser accepts the auto_publish, tables, and macros blocks shown below, but does not interpret them yet. Database sources are not yet supported; Martin logs a warning and skips the entire entry.

# Keep serving the working GeoParquet sources when the database source is skipped.
on_invalid: warn
duckdb:
  pool_size: 4
  auto_bounds: quick
  sources:
    - database: /data/tiles.duckdb
      auto_publish:
        tables:
          from_schemas: autodetect
          source_id_format: "{table}"
          id_columns: [id, gid]
          extent: 4096
          buffer: 64
          clip_geom: true
      tables:
        roads:
          schema: main
          table: roads
          geometry_column: geom
          srid: 4326
          minzoom: 0
          maxzoom: 14
          properties:
            id: int4
            name: varchar

Without on_invalid: warn, the default abort policy stops Martin because the database entry cannot be resolved. Do not rely on any of the database source options above yet; they are included to show the accepted configuration shape only.

About GeoParquet

GeoParquet is a Parquet file with geospatial metadata.

Parquet is a columnar file format. GeoParquet adds a standard way to store geometry columns and CRS information inside that file.

Martin reads GeoParquet with DuckDB read_parquet, loads the DuckDB spatial extension, and generates MVT tiles on each request. Remote URLs also load the DuckDB httpfs extension.

Martin passes remote URLs to DuckDB unchanged and does not manage credentials for them. Public buckets work with no further configuration. Private ones need DuckDB's own credential configuration, such as the standard AWS environment variables.

You may want to visit these specs:

• GeoParquet
• Parquet
• DuckDB spatial