Using mixin for optimizer_hints support

Author: RoderickJDunn

docs/intro.md

@@ -463,6 +463,8 @@ List of available abstract mixins:
 
 - `AbstractMixin_TimeTravel` - Only snowflake & bigquery
 
+- `AbstractMixin_OptimizerHints` - Only oracle & mysql
+
 More will be added in the future.
 
 Note that it's still possible to use user-defined mixins that aren't on this list.

sqeleton/abcs/database_types.py

@@ -201,10 +201,6 @@ def offset_limit(self, offset: Optional[int] = None, limit: Optional[int] = None
     def explain_as_text(self, query: str) -> str:
         "Provide SQL for explaining a query, returned as table(varchar)"
 
-    @abstractmethod
-    def optimizer_hints(self, hints: str) -> str:
-        "Provide SQL for enclosing optimizer hints"
-
     @abstractmethod
     def timestamp_value(self, t: datetime) -> str:
         "Provide SQL for the given timestamp value"

sqeleton/abcs/mixins.py

@@ -145,3 +145,15 @@ def time_travel(
 
         Must specify exactly one of `timestamp`, `offset` or `statement`.
         """
+
+class AbstractMixin_OptimizerHints(AbstractMixin):
+    @abstractmethod
+    def optimizer_hints(
+        self,
+        optimizer_hints: str
+    ) -> str:
+        """Creates a compatible optimizer_hints string
+
+        Parameters:
+            optimizer_hints - string of opimizer hints
+        """

sqeleton/databases/base.py

@@ -36,7 +36,12 @@
     Boolean,
 )
 from ..abcs.mixins import Compilable
-from ..abcs.mixins import AbstractMixin_Schema, AbstractMixin_RandomSample, AbstractMixin_NormalizeValue
+from ..abcs.mixins import (
+    AbstractMixin_Schema,
+    AbstractMixin_RandomSample,
+    AbstractMixin_NormalizeValue,
+    AbstractMixin_OptimizerHints
+) 
 from ..bound_exprs import bound_table
 
 logger = logging.getLogger("database")
@@ -134,6 +139,14 @@ def random_sample_ratio_approx(self, tbl: AbstractTable, ratio: float) -> Abstra
         return tbl.where(Random() < ratio)
 
 
+class Mixin_OptimizerHints(AbstractMixin_OptimizerHints):
+    def optimizer_hints(
+        self,
+        hints: str
+    ) -> str:
+        return f"/*+ {hints} */ "
+
+
 class BaseDialect(AbstractDialect):
     SUPPORTS_PRIMARY_KEY = False
     SUPPORTS_INDEXES = False
@@ -168,8 +181,6 @@ def current_timestamp(self) -> str:
     def explain_as_text(self, query: str) -> str:
         return f"EXPLAIN {query}"
 
-    def optimizer_hints(self, hints: str) -> str:
-        raise NotImplementedError(f"Optimizer hints not yet implemented in {self.__class__}")
 
     def _constant_value(self, v):
         if v is None:

sqeleton/databases/mysql.py

@@ -17,7 +17,7 @@
     AbstractMixin_Regex,
     AbstractMixin_RandomSample,
 )
-from .base import ThreadedDatabase, import_helper, ConnectError, BaseDialect, Compilable
+from .base import Mixin_OptimizerHints, ThreadedDatabase, import_helper, ConnectError, BaseDialect, Compilable
 from .base import MD5_HEXDIGITS, CHECKSUM_HEXDIGITS, TIMESTAMP_PRECISION_POS, Mixin_Schema, Mixin_RandomSample
 from ..queries.ast_classes import BinBoolOp
 
@@ -54,7 +54,7 @@ def test_regex(self, string: Compilable, pattern: Compilable) -> Compilable:
         return BinBoolOp("REGEXP", [string, pattern])
 
 
-class Dialect(BaseDialect, Mixin_Schema):
+class Dialect(BaseDialect, Mixin_Schema, Mixin_OptimizerHints):
     name = "MySQL"
     ROUNDS_ON_PREC_LOSS = True
     SUPPORTS_PRIMARY_KEY = True

sqeleton/databases/oracle.py

@@ -17,7 +17,7 @@
 from ..abcs.mixins import AbstractMixin_MD5, AbstractMixin_NormalizeValue, AbstractMixin_Schema
 from ..abcs import Compilable
 from ..queries import this, table, SKIP
-from .base import BaseDialect, ThreadedDatabase, import_helper, ConnectError, QueryError, Mixin_RandomSample
+from .base import BaseDialect, Mixin_OptimizerHints, ThreadedDatabase, import_helper, ConnectError, QueryError, Mixin_RandomSample
 from .base import TIMESTAMP_PRECISION_POS
 
 SESSION_TIME_ZONE = None  # Changed by the tests
@@ -72,7 +72,7 @@ def list_tables(self, table_schema: str, like: Compilable = None) -> Compilable:
         )
 
 
-class Dialect(BaseDialect, Mixin_Schema):
+class Dialect(BaseDialect, Mixin_Schema, Mixin_OptimizerHints):
     name = "Oracle"
     SUPPORTS_PRIMARY_KEY = True
     SUPPORTS_INDEXES = True
@@ -130,9 +130,6 @@ def constant_values(self, rows) -> str:
     def explain_as_text(self, query: str) -> str:
         raise NotImplementedError("Explain not yet implemented in Oracle")
 
-    def optimizer_hints(self, s: str):
-        return f"/*+ {s} */ "
-
     def parse_type(
         self,
         table_path: DbPath,