introduce tokenizer modules

[nominatim.git] / nominatim / tokenizer / factory.py

diff --git a/nominatim/tokenizer/factory.py b/nominatim/tokenizer/factory.py
new file mode 100644 (file)
index 0000000..1079c93
--- /dev/null
+++ b/nominatim/tokenizer/factory.py
@@ -0,0 +1,84 @@
+"""
+Functions for creating a tokenizer or initialising the right one for an
+existing database.
+
+A tokenizer is something that is bound to the lifetime of a database. It
+can be choosen and configured before the intial import but then needs to
+be used consistently when querying and updating the database.
+
+This module provides the functions to create and configure a new tokenizer
+as well as instanciating the appropriate tokenizer for updating an existing
+database.
+
+A tokenizer usually also includes PHP code for querying. The appropriate PHP
+normalizer module is installed, when the tokenizer is created.
+"""
+import logging
+import importlib
+
+from ..errors import UsageError
+from ..db import properties
+from ..db.connection import connect
+
+LOG = logging.getLogger()
+
+def _import_tokenizer(name):
+    """ Load the tokenizer.py module from project directory.
+    """
+    try:
+        return importlib.import_module('nominatim.tokenizer.' + name + '_tokenizer')
+    except ModuleNotFoundError as exp:
+        LOG.fatal("No tokenizer named '%s' available. "
+                  "Check the setting of NOMINATIM_TOKENIZER.", name)
+        raise UsageError('Tokenizer not found') from exp
+
+
+def create_tokenizer(config):
+    """ Create a new tokenizer as defined by the given configuration.
+
+        The tokenizer data and code is copied into the 'tokenizer' directory
+        of the project directory and the tokenizer loaded from its new location.
+    """
+    # Create the directory for the tokenizer data
+    basedir = config.project_dir / 'tokenizer'
+    if not basedir.exists():
+        basedir.mkdir()
+    elif not basedir.is_dir():
+        LOG.fatal("Tokenizer directory '%s' cannot be created.", basedir)
+        raise UsageError("Tokenizer setup failed.")
+
+    tokenizer_module = _import_tokenizer(config.TOKENIZER)
+
+    tokenizer = tokenizer_module.create(config.get_libpq_dsn(), basedir)
+    tokenizer.init_new_db(config)
+
+    with connect(config.get_libpq_dsn()) as conn:
+        properties.set_property(conn, 'tokenizer', config.TOKENIZER)
+
+    return tokenizer
+
+
+def get_tokenizer_for_db(config):
+    """ Instantiate a tokenizer for an existing database.
+
+        The function looks up the appropriate tokenizer in the database
+        and initialises it.
+    """
+    basedir = config.project_dir / 'tokenizer'
+    if not basedir.is_dir():
+        LOG.fatal("Cannot find tokenizer data in '%s'.", basedir)
+        raise UsageError('Cannot initialize tokenizer.')
+
+    with connect(config.get_libpq_dsn()) as conn:
+        name = properties.get_property(conn, 'tokenizer')
+
+    if name is None:
+        LOG.fatal("Tokenizer was not set up properly. Database property missing.")
+        raise UsageError('Cannot initialize tokenizer.')
+
+    tokenizer_module = _import_tokenizer(name)
+
+    tokenizer = tokenizer_module.create(config.get_libpq_dsn(), basedir)
+    tokenizer.init_from_project()
+
+    return tokenizer