port database setup function to python

[nominatim.git] / nominatim / db / connection.py

diff --git a/nominatim/db/connection.py b/nominatim/db/connection.py
index 8e75d7a271578f559d7015845d5cde867faa08cb..12f5f4e15f8c55b57c5fc68b93154942a9839c3c 100644 (file)
--- a/nominatim/db/connection.py
+++ b/nominatim/db/connection.py
@@ -1,12 +1,18 @@
 """
 Specialised connection and cursor functions.
 """
+import contextlib
 import logging
+import os
 
 import psycopg2
 import psycopg2.extensions
 import psycopg2.extras
 
+from ..errors import UsageError
+
+LOG = logging.getLogger()
+
 class _Cursor(psycopg2.extras.DictCursor):
     """ A cursor returning dict-like objects and providing specialised
         execution functions.
@@ -15,8 +21,7 @@ class _Cursor(psycopg2.extras.DictCursor):
     def execute(self, query, args=None): # pylint: disable=W0221
         """ Query execution that logs the SQL query when debugging is enabled.
         """
-        logger = logging.getLogger()
-        logger.debug(self.mogrify(query, args).decode('utf-8'))
+        LOG.debug(self.mogrify(query, args).decode('utf-8'))
 
         super().execute(query, args)
 
@@ -27,7 +32,7 @@ class _Cursor(psycopg2.extras.DictCursor):
         self.execute(sql, args)
 
         if self.rowcount != 1:
-            raise ValueError("Query did not return a single row.")
+            raise RuntimeError("Query did not return a single row.")
 
         return self.fetchone()[0]
 
@@ -42,17 +47,115 @@ class _Connection(psycopg2.extensions.connection):
         """
         return super().cursor(cursor_factory=cursor_factory, **kwargs)
 
+
     def table_exists(self, table):
         """ Check that a table with the given name exists in the database.
         """
         with self.cursor() as cur:
             num = cur.scalar("""SELECT count(*) FROM pg_tables
-                                WHERE tablename = %s""", (table, ))
+                                WHERE tablename = %s and schemaname = 'public'""", (table, ))
             return num == 1
 
 
+    def index_exists(self, index, table=None):
+        """ Check that an index with the given name exists in the database.
+            If table is not None then the index must relate to the given
+            table.
+        """
+        with self.cursor() as cur:
+            cur.execute("""SELECT tablename FROM pg_indexes
+                           WHERE indexname = %s and schemaname = 'public'""", (index, ))
+            if cur.rowcount == 0:
+                return False
+
+            if table is not None:
+                row = cur.fetchone()
+                return row[0] == table
+
+        return True
+
+
+    def server_version_tuple(self):
+        """ Return the server version as a tuple of (major, minor).
+            Converts correctly for pre-10 and post-10 PostgreSQL versions.
+        """
+        version = self.server_version
+        if version < 100000:
+            return (int(version / 10000), (version % 10000) / 100)
+
+        return (int(version / 10000), version % 10000)
+
+
+    def postgis_version_tuple(self):
+        """ Return the postgis version installed in the database as a
+            tuple of (major, minor). Assumes that the PostGIS extension
+            has been installed already.
+        """
+        with self.cursor() as cur:
+            version = cur.scalar('SELECT postgis_lib_version()')
+
+        return tuple((int(x) for x in version.split('.')[:2]))
+
+
 def connect(dsn):
     """ Open a connection to the database using the specialised connection
-        factory.
+        factory. The returned object may be used in conjunction with 'with'.
+        When used outside a context manager, use the `connection` attribute
+        to get the connection.
+    """
+    try:
+        conn = psycopg2.connect(dsn, connection_factory=_Connection)
+        ctxmgr = contextlib.closing(conn)
+        ctxmgr.connection = conn
+        return ctxmgr
+    except psycopg2.OperationalError as err:
+        raise UsageError("Cannot connect to database: {}".format(err)) from err
+
+
+# Translation from PG connection string parameters to PG environment variables.
+# Derived from https://www.postgresql.org/docs/current/libpq-envars.html.
+_PG_CONNECTION_STRINGS = {
+    'host': 'PGHOST',
+    'hostaddr': 'PGHOSTADDR',
+    'port': 'PGPORT',
+    'dbname': 'PGDATABASE',
+    'user': 'PGUSER',
+    'password': 'PGPASSWORD',
+    'passfile': 'PGPASSFILE',
+    'channel_binding': 'PGCHANNELBINDING',
+    'service': 'PGSERVICE',
+    'options': 'PGOPTIONS',
+    'application_name': 'PGAPPNAME',
+    'sslmode': 'PGSSLMODE',
+    'requiressl': 'PGREQUIRESSL',
+    'sslcompression': 'PGSSLCOMPRESSION',
+    'sslcert': 'PGSSLCERT',
+    'sslkey': 'PGSSLKEY',
+    'sslrootcert': 'PGSSLROOTCERT',
+    'sslcrl': 'PGSSLCRL',
+    'requirepeer': 'PGREQUIREPEER',
+    'ssl_min_protocol_version': 'PGSSLMINPROTOCOLVERSION',
+    'ssl_max_protocol_version': 'PGSSLMAXPROTOCOLVERSION',
+    'gssencmode': 'PGGSSENCMODE',
+    'krbsrvname': 'PGKRBSRVNAME',
+    'gsslib': 'PGGSSLIB',
+    'connect_timeout': 'PGCONNECT_TIMEOUT',
+    'target_session_attrs': 'PGTARGETSESSIONATTRS',
+}
+
+
+def get_pg_env(dsn, base_env=None):
+    """ Return a copy of `base_env` with the environment variables for
+        PostgresSQL set up from the given database connection string.
+        If `base_env` is None, then the OS environment is used as a base
+        environment.
     """
-    return psycopg2.connect(dsn, connection_factory=_Connection)
+    env = dict(base_env if base_env is not None else os.environ)
+
+    for param, value in psycopg2.extensions.parse_dsn(dsn).items():
+        if param in _PG_CONNECTION_STRINGS:
+            env[_PG_CONNECTION_STRINGS[param]] = value
+        else:
+            LOG.error("Unknown connection parameter '%s' ignored.", param)
+
+    return env