mirror of
https://github.com/simonw/sqlite-utils.git
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125 lines
4 KiB
Python
125 lines
4 KiB
Python
import os
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from .db import Database, Table
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SPATIALITE_PATHS = (
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"/usr/lib/x86_64-linux-gnu/mod_spatialite.so",
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"/usr/local/lib/mod_spatialite.dylib",
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)
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def find_spatialite() -> str:
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"""
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The ``find_spatialite()`` function searches for the `SpatiaLite <https://www.gaia-gis.it/fossil/libspatialite/index>`__ SQLite extension in some common places. It returns a string path to the location, or ``None`` if SpatiaLite was not found.
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You can use it in code like this:
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.. code-block:: python
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from sqlite_utils import Database
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from sqlite_utils.gis import find_spatialite
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db = Database("mydb.db")
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spatialite = find_spatialite()
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if spatialite:
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db.conn.enable_load_extension(True)
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db.conn.load_extension(spatialite)
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"""
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for path in SPATIALITE_PATHS:
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if os.path.exists(path):
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return path
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return None
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def init_spatialite(db: Database, path: str) -> None:
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"""
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The ``init_spatialite`` function will load and initalize the Spatialite extension.
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The ``path`` argument should be an absolute path to the compiled extension, which
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can be found using ``find_spatialite``.
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.. code-block:: python
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from sqlite_utils.gis import find_spatialite, init_spatialite
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db = Database("mydb.db")
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init_spatialite(db, find_spatialite())
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If you've installed Spatialite somewhere unexpected (for testing an alternate version, for example)
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you can pass in an absolute path:
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.. code-block:: python
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.. code-block:: python
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from sqlite_utils.gis import init_spatialite
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db = Database("mydb.db")
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init_spatialite(db, "./local/mod_spatialite.dylib")
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"""
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db.conn.enable_load_extension(True)
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db.conn.load_extension(path)
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# Initialize SpatiaLite if not yet initialized
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if "spatial_ref_sys" in db.table_names():
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return
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db.execute("select InitSpatialMetadata(1)")
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def add_geometry_column(
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table: Table,
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geometry_type: str,
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column_name: str = "geometry",
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srid: int = 4326,
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coord_dimension: str = "XY",
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not_null: bool = False,
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) -> None:
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"""
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In Spatialite, a geometry column can only be added to an existing table.
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To do so, use ``add_geometry_column``, passing in a :ref:`table <reference_db_table>`
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and geometry type.
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By default, this will add a nullable column called ``geometry`` using
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`SRID 4326 <https://spatialreference.org/ref/epsg/wgs-84/>`__. These can be customized using
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the ``column_name`` and ``srid`` arguments.
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.. code-block:: python
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from sqlite_utils.gis import find_spatialite, init_spatialite, add_geometry_column
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db = Database("mydb.db")
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init_spatialite(db, find_spatialite())
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# the table must exist before adding a geometry column
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db["locations"].create({"name": str})
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add_geometry_column(db["locations"], "POINT")
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"""
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table.db.execute(
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"SELECT AddGeometryColumn(?, ?, ?, ?, ?, ?);",
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[table.name, column_name, srid, geometry_type, coord_dimension, int(not_null)],
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)
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def create_spatial_index(table: Table, column_name: str = "geometry") -> None:
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"""
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A spatial index allows for significantly faster bounding box queries.
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To create on, use ``create_spatial_index`` with a :ref:`table <reference_db_table>`
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and the name of an existing geometry column.
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.. code-block:: python
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from sqlite_utils.gis import add_geometry_column, create_spatial_index
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# assuming Spatialite is loaded, create the table, add the column
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db["locations"].create({"name": str})
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add_geometry_column(db["locations"], "POINT", "geometry")
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# now we can index it
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create_spatial_index(db["locations"], "geometry")
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# the spatial index is a virtual table, which we can inspect
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print(db["idx_locations_geometry"].schema)
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# outputs:
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# CREATE VIRTUAL TABLE "idx_locations_geometry" USING rtree(pkid, xmin, xmax, ymin, ymax)
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"""
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table.db.execute("select CreateSpatialIndex(?, ?)", [table.name, column_name])
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