SA14: Enable SQL compilation caching for CrateDialect and friends

This patch follows the documentation at [1] and adds the attributes
`supports_statement_cache`, `cache_ok` and `inherit_cache` to the
corresponding classes of `CrateDialect`, `UserDefinedType` and
`ColumnElement`.

The test suite thoroughly accepted this change of setting all attributes
to `True`, effectively fully supporting SQL compilation caching.

[1] https://docs.sqlalchemy.org/en/14/faq/performance.html

Author: amotl

src/crate/client/sqlalchemy/dialect.py

@@ -167,6 +167,7 @@ class CrateDialect(default.DefaultDialect):
     ddl_compiler = CrateDDLCompiler
     type_compiler = CrateTypeCompiler
     supports_native_boolean = True
+    supports_statement_cache = True
     colspecs = colspecs
     implicit_returning = True
 

src/crate/client/sqlalchemy/predicates/__init__.py

@@ -24,6 +24,7 @@
 
 
 class Match(ColumnElement):
+    inherit_cache = True
 
     def __init__(self, column, term, match_type=None, options=None):
         super(Match, self).__init__()

src/crate/client/sqlalchemy/types.py

@@ -132,6 +132,7 @@ def __eq__(self, other):
 
 
 class _Craty(sqltypes.UserDefinedType):
+    cache_ok = True
 
     class Comparator(sqltypes.TypeEngine.Comparator):
 
@@ -165,6 +166,7 @@ class Any(expression.ColumnElement):
 
     """
     __visit_name__ = 'any'
+    inherit_cache = True
 
     def __init__(self, left, right, operator=operators.eq):
         self.type = sqltypes.Boolean()
@@ -174,6 +176,7 @@ def __init__(self, left, right, operator=operators.eq):
 
 
 class _ObjectArray(sqltypes.UserDefinedType):
+    cache_ok = True
 
     class Comparator(sqltypes.TypeEngine.Comparator):
         def __getitem__(self, key):
@@ -222,6 +225,7 @@ def get_col_spec(self, **kws):
 
 
 class Geopoint(sqltypes.UserDefinedType):
+    cache_ok = True
 
     class Comparator(sqltypes.TypeEngine.Comparator):
 
@@ -247,6 +251,7 @@ def result_processor(self, dialect, coltype):
 
 
 class Geoshape(sqltypes.UserDefinedType):
+    cache_ok = True
 
     class Comparator(sqltypes.TypeEngine.Comparator):