Collapse build_sql into _fetch (#953)

This was getting so short that it made sense to go back from whence it came.

beets/dbcore/db.py

@@ -24,7 +24,7 @@ import collections
 
 import beets
 from beets.util.functemplate import Template
-from .query import MatchQuery, build_sql
+from .query import MatchQuery, NullSort
 from .types import BASE_TYPE
 
 
@@ -745,19 +745,30 @@ class Database(object):
 
     # Querying.
 
-    def _fetch(self, model_cls, query, sort_order=None):
+    def _fetch(self, model_cls, query, sort=None):
         """Fetch the objects of type `model_cls` matching the given
         query. The query may be given as a string, string sequence, a
-        Query object, or None (to fetch everything). If provided,
-       `sort_order` is either a SQLite ORDER BY clause for sorting or a
-        Sort object.
+        Query object, or None (to fetch everything). `sort` is an
+        optional Sort object.
         """
-        sql, subvals, query, sort = build_sql(model_cls, query, sort_order)
+        where, subvals = query.clause()
+        sort = sort or NullSort()
+        order_by = sort.order_clause()
+
+        sql = ("SELECT * FROM {0} WHERE {1} {2}").format(
+            model_cls._table,
+            where or '1',
+            "ORDER BY {0}".format(order_by) if order_by else '',
+        )
 
         with self.transaction() as tx:
             rows = tx.query(sql, subvals)
 
-        return Results(model_cls, rows, self, query, sort)
+        return Results(
+            model_cls, rows, self,
+            None if where else query,  # Slow query component.
+            sort if sort.is_slow() else None,  # Slow sort component.
+        )
 
     def _get(self, model_cls, id):
         """Get a Model object by its id or None if the id does not

beets/dbcore/query.py

@@ -655,31 +655,3 @@ class NullSort(Sort):
 
     def __nonzero__(self):
         return False
-
-
-def build_sql(model_cls, query, sort):
-    """ Generate a sql statement (and the values that must be injected into it)
-    from a query, sort and a model class. Query and sort objects are returned
-    only for slow query and slow sort operation.
-    """
-    where, subvals = query.clause()
-    if where is not None:
-        query = None
-
-    if not sort:
-        sort_order = ""
-        sort = None
-    elif isinstance(sort, Sort):
-        order_clause = sort.order_clause()
-        sort_order = "ORDER BY {0}".format(order_clause) \
-            if order_clause else ""
-        if not sort.is_slow():
-            sort = None
-
-    sql = ("SELECT * FROM {table} WHERE {query_clause} {sort_order}").format(
-        table=model_cls._table,
-        query_clause=where or '1',
-        sort_order=sort_order,
-    )
-
-    return sql, subvals, query, sort