Make sure that PostgreSQLProvider.get_fields returns valid json schem… (#1312)

* Make sure that PostgreSQLProvider.get_fields returns valid json schema types

* Log warnings when postgres provider encounters unknown types

* Update postgresql.py

---------

Co-authored-by: Tom Kralidis <tomkralidis@gmail.com>

pygeoapi/provider/base.py

@@ -82,7 +82,9 @@ class BaseProvider:
         """
         Get provider field information (names, types)
 
-        :returns: dict of fields
+        Example response: {'field1': 'string', 'field2': 'number'}}
+
+        :returns: dict of field names and their associated JSON Schema typess
         """
 
         raise NotImplementedError()

pygeoapi/provider/postgresql.py

@@ -187,13 +187,37 @@ class PostgreSQLProvider(BaseProvider):
         """
         LOGGER.debug('Get available fields/properties')
 
-        fields = {}
-        for column in self.table_model.__table__.columns:
-            fields[str(column.name)] = {'type': str(column.type)}
+        # sql-schema only allows these types, so we need to map from sqlalchemy
+        # string, number, integer, object, array, boolean, null,
+        # https://json-schema.org/understanding-json-schema/reference/type.html
+        column_type_map = {
+            str: 'string',
+            float: 'number',
+            int: 'integer',
+            bool: 'boolean',
+        }
+        default_value = 'string'
 
-        fields.pop(self.geom)  # Exclude geometry column
+        def _column_type_to_json_schema_type(column_type):
+            try:
+                python_type = column_type.python_type
+            except NotImplementedError:
+                LOGGER.warning(f'Unsupported column type {column_type}')
+                return default_value
+            else:
+                try:
+                    return column_type_map[python_type]
+                except KeyError:
+                    LOGGER.warning(f'Unsupported column type {column_type}')
+                    return default_value
 
-        return fields
+        return {
+            str(column.name): {
+                'type': _column_type_to_json_schema_type(column.type)
+            }
+            for column in self.table_model.__table__.columns
+            if column.name != self.geom  # Exclude geometry column
+        }
 
     def get(self, identifier, crs_transform_spec=None, **kwargs):
         """

tests/test_postgresql_provider.py

@@ -308,18 +308,18 @@ def test_query_cql_properties_bbox_filters(config):
 def test_get_fields(config):
     # Arrange
     expected_fields = {
-        'blockage': {'type': 'VARCHAR(80)'},
-        'covered': {'type': 'VARCHAR(80)'},
-        'depth': {'type': 'VARCHAR(80)'},
-        'layer': {'type': 'VARCHAR(80)'},
-        'name': {'type': 'VARCHAR(80)'},
-        'natural': {'type': 'VARCHAR(80)'},
-        'osm_id': {'type': 'INTEGER'},
-        'tunnel': {'type': 'VARCHAR(80)'},
-        'water': {'type': 'VARCHAR(80)'},
-        'waterway': {'type': 'VARCHAR(80)'},
-        'width': {'type': 'VARCHAR(80)'},
-        'z_index': {'type': 'VARCHAR(80)'}
+        'blockage': {'type': 'string'},
+        'covered': {'type': 'string'},
+        'depth': {'type': 'string'},
+        'layer': {'type': 'string'},
+        'name': {'type': 'string'},
+        'natural': {'type': 'string'},
+        'osm_id': {'type': 'integer'},
+        'tunnel': {'type': 'string'},
+        'water': {'type': 'string'},
+        'waterway': {'type': 'string'},
+        'width': {'type': 'string'},
+        'z_index': {'type': 'string'}
     }
 
     # Act