Add new gis.py module with spatialite helper methods

sqlite_utils/gis.py

@@ -0,0 +1,44 @@
+import os
+from .db import Database, Table
+
+SPATIALITE_PATHS = (
+    "/usr/lib/x86_64-linux-gnu/mod_spatialite.so",
+    "/usr/local/lib/mod_spatialite.dylib",
+)
+
+
+def find_spatialite() -> str:
+    for path in SPATIALITE_PATHS:
+        if os.path.exists(path):
+            return path
+    return None
+
+
+def init_spatialite(db: Database, path: str) -> None:
+    "Load spatialite extension for a database"
+    db.conn.enable_load_extension(True)
+    db.conn.load_extension(path)
+    # Initialize SpatiaLite if not yet initialized
+    if "spatial_ref_sys" in db.table_names():
+        return
+    db.conn.execute("select InitSpatialMetadata(1)")
+
+
+def add_geometry_column(
+    table: Table,
+    geometry_type: str,
+    column_name: str = "geometry",
+    srid: int = 4326,
+    coord_dimension: str = "XY",
+    not_null: bool = False,
+) -> None:
+    "Add a geometry column to a table"
+    table.db.conn.execute(
+        "SELECT AddGeometryColumn(?, ?, ?, ?, ?, ?);",
+        [table.name, column_name, srid, geometry_type, coord_dimension, int(not_null)],
+    )
+
+
+def create_spatial_index(table: Table, column_name: str = "geometry") -> None:
+    "Create a spatial index for a table and column"
+    table.db.conn.execute("select CreateSpatialIndex(?, ?)", [table.name, column_name])