sqlite-utils index-foreign-keys / db.index_foreign_keys()

Closes #33

sqlite_utils/cli.py

@@ -217,6 +217,20 @@ def add_foreign_key(path, table, column, other_table, other_column):
         raise click.ClickException(e)
 
 
+@cli.command(name="index-foreign-keys")
+@click.argument(
+    "path",
+    type=click.Path(exists=True, file_okay=True, dir_okay=False, allow_dash=False),
+    required=True,
+)
+def index_foreign_keys(path):
+    """
+    Ensure every foreign key column has an index on it.
+    """
+    db = sqlite_utils.Database(path)
+    db.index_foreign_keys()
+
+
 @cli.command(name="create-index")
 @click.argument(
     "path",

sqlite_utils/db.py

@@ -315,6 +315,16 @@ class Database:
         # can see the newly created foreign key.
         self.vacuum()
 
+    def index_foreign_keys(self):
+        for table_name in self.table_names():
+            table = self[table_name]
+            existing_indexes = {
+                i.columns[0] for i in table.indexes if len(i.columns) == 1
+            }
+            for fk in table.foreign_keys:
+                if fk.column not in existing_indexes:
+                    table.create_index([fk.column])
+
     def vacuum(self):
         self.conn.execute("VACUUM;")