HStoreIndex, unique indexes on hstore keys

localized_fields/hstore_index.py

@@ -0,0 +1,130 @@
+from typing import List
+
+from django.db import models
+
+
+class HStoreIndex(models.Index):
+    """Allows creating a index on a specific HStore index.
+
+    Note: pieces of code in this class have been copied
+    from the base class. There was no way around this."""
+
+    def __init__(self, field: str, keys: List[str], unique: bool=False,
+                 name: str=''):
+        """Initializes a new instance of :see:HStoreIndex.
+
+        Arguments:
+            field:
+                Name of the hstore field for
+                which's keys to create a index for.
+
+            keys:
+                The name of the hstore keys to
+                create the index on.
+
+            unique:
+                Whether this index should
+                be marked as UNIQUE.
+
+            name:
+                The name of the index. If left
+                empty, one will be generated.
+        """
+
+        self.field = field
+        self.keys = keys
+        self.unique = unique
+
+        # this will eventually set self.name
+        super(HStoreIndex, self).__init__(
+            fields=[field],
+            name=name
+        )
+
+    def get_sql_create_template_values(self, model, schema_editor, using):
+        """Gets the values for the SQL template.
+
+        Arguments:
+            model:
+                The model this index applies to.
+
+            schema_editor:
+                The schema editor to modify the schema.
+
+            using:
+                Optional: "USING" statement.
+
+        Returns:
+            Dictionary of keys to pass into the SQL template.
+        """
+
+        fields = [model._meta.get_field(field_name) for field_name, order in self.fields_orders]
+        tablespace_sql = schema_editor._get_index_tablespace_sql(model, fields)
+        quote_name = schema_editor.quote_name
+
+        columns = [
+            '(%s->\'%s\')' % (self.field, key)
+            for key in self.keys
+        ]
+
+        return {
+            'table': quote_name(model._meta.db_table),
+            'name': quote_name(self.name),
+            'columns': ', '.join(columns),
+            'using': using,
+            'extra': tablespace_sql,
+        }
+
+    def create_sql(self, model, schema_editor, using=''):
+        """Gets the SQL to execute when creating the index.
+
+        Arguments:
+            model:
+                The model this index applies to.
+
+            schema_editor:
+                The schema editor to modify the schema.
+
+            using:
+                Optional: "USING" statement.
+
+        Returns:
+            SQL string to execute to create this index.
+        """
+
+        sql_create_index = schema_editor.sql_create_index
+        if self.unique:
+            sql_create_index = sql_create_index.replace('CREATE', 'CREATE UNIQUE')
+        sql_parameters = self.get_sql_create_template_values(model, schema_editor, using)
+        return sql_create_index % sql_parameters
+
+    def remove_sql(self, model, schema_editor):
+        """Gets the SQL to execute to remove this index.
+
+        Arguments:
+            model:
+                The model this index applies to.
+
+            schema_editor:
+                The schema editor to modify the schema.
+
+        Returns:
+            SQL string to execute to remove this index.
+        """
+        quote_name = schema_editor.quote_name
+        return schema_editor.sql_delete_index % {
+            'table': quote_name(model._meta.db_table),
+            'name': quote_name(self.name),
+        }
+
+    def deconstruct(self):
+        """Gets the values to pass to :see:__init__ when
+        re-creating this object."""
+
+        path = '%s.%s' % (self.__class__.__module__, self.__class__.__name__)
+        return (path, (), {
+            'field': self.field,
+            'keys': self.keys,
+            'unique': self.unique,
+            'name': self.name
+        })