Add minimal SQLAlchemy 1.4 compatibility for CrateCompiler

> A major initiative in the 1.4 series is to approach the model of both
Core SQL statements as well as the ORM Query to allow for an efficient,
cacheable model of statement creation and compilation, where the
compilation step would be cached, based on a cache key generated by the
created statement object, which itself is newly created for each use.

While there is probably more to it, this patch tries to at least make
the CrateCompiler work with the new subsystem infrastructure.

src/crate/client/sqlalchemy/compiler.py

@@ -26,7 +26,7 @@
 from sqlalchemy.sql import crud
 from sqlalchemy.sql import compiler
 from .types import MutableDict
-from .sa_version import SA_1_1, SA_VERSION
+from .sa_version import SA_1_1, SA_1_4, SA_VERSION
 
 
 def rewrite_update(clauseelement, multiparams, params):
@@ -198,7 +198,20 @@ def visit_insert(self, insert_stmt, asfrom=False, **kw):
              "selectable": insert_stmt})
 
         self.isinsert = True
-        crud_params = crud._get_crud_params(self, insert_stmt, **kw)
+
+        if SA_VERSION >= SA_1_4:
+            # Minimal patch to be compatible with SQLAlchemy 1.4.
+            # For a more thorough implementation, please follow
+            # https://github.com/crate/crate-python/pull/391.
+            compile_state = insert_stmt._compile_state_factory(
+                insert_stmt, self, **kw
+            )
+            insert_stmt = compile_state.statement
+            crud_params = crud._get_crud_params(self, insert_stmt, compile_state, **kw)
+            _has_multi_parameters = compile_state._has_multi_parameters
+        else:
+            crud_params = crud._get_crud_params(self, insert_stmt, **kw)
+            _has_multi_parameters = insert_stmt._has_multi_parameters
 
         if not crud_params and \
                 not self.dialect.supports_default_values and \
@@ -207,7 +220,7 @@ def visit_insert(self, insert_stmt, asfrom=False, **kw):
                 "The '%s' dialect with current database version settings does "
                 "not support empty inserts." % self.dialect.name)
 
-        if insert_stmt._has_multi_parameters:
+        if _has_multi_parameters:
             if not self.dialect.supports_multivalues_insert:
                 raise NotImplementedError(
                     "The '%s' dialect with current database "
@@ -262,7 +275,7 @@ def visit_insert(self, insert_stmt, asfrom=False, **kw):
             text += " (%s)" % self.process(self._insert_from_select, **kw)
         elif not crud_params and supports_default_values:
             text += " DEFAULT VALUES"
-        elif insert_stmt._has_multi_parameters:
+        elif _has_multi_parameters:
             text += " VALUES %s" % (
                 ", ".join(
                     "(%s)" % (
@@ -294,7 +307,16 @@ def visit_update(self, update_stmt, **kw):
 
         self.isupdate = True
 
-        extra_froms = update_stmt._extra_froms
+        if SA_VERSION >= SA_1_4:
+            # Minimal patch to be compatible with SQLAlchemy 1.4.
+            # For a more thorough implementation, please follow
+            # https://github.com/crate/crate-python/pull/391.
+            compile_state = update_stmt._compile_state_factory(
+                update_stmt, compiler, **kw
+            )
+            extra_froms = compile_state._extra_froms
+        else:
+            extra_froms = update_stmt._extra_froms
 
         text = 'UPDATE '
 
@@ -351,10 +373,21 @@ def visit_update(self, update_stmt, **kw):
             if extra_from_text:
                 text += " " + extra_from_text
 
-        if update_stmt._whereclause is not None:
-            t = self.process(update_stmt._whereclause)
-            if t:
-                text += " WHERE " + t
+        if SA_VERSION >= SA_1_4:
+            # Minimal patch to be compatible with SQLAlchemy 1.4.
+            # For a more thorough implementation, please follow
+            # https://github.com/crate/crate-python/pull/391.
+            if update_stmt._where_criteria:
+                t = self._generate_delimited_and_list(
+                    update_stmt._where_criteria, **kw
+                )
+                if t:
+                    text += " WHERE " + t
+        else:
+            if update_stmt._whereclause is not None:
+                t = self.process(update_stmt._whereclause)
+                if t:
+                    text += " WHERE " + t
 
         limit_clause = self.update_limit_clause(update_stmt)
         if limit_clause:
@@ -384,20 +417,33 @@ def _get_crud_params(compiler, stmt, **kw):
                                                 required=True))
                     for c in stmt.table.columns]
 
-        if stmt._has_multi_parameters:
-            stmt_parameters = stmt.parameters[0]
-        else:
-            stmt_parameters = stmt.parameters
-
         # getters - these are normally just column.key,
         # but in the case of mysql multi-table update, the rules for
         # .key must conditionally take tablename into account
-        if SA_VERSION >= SA_1_1:
+        if SA_VERSION >= SA_1_4:
+            # Minimal patch to be compatible with SQLAlchemy 1.4.
+            # For a more thorough implementation, please follow
+            # https://github.com/crate/crate-python/pull/391.
+            compile_state = stmt._compile_state_factory(
+                stmt, compiler, **kw
+            )
+            stmt = compile_state.statement
+            _column_as_key, _getattr_col_key, _col_bind_name = \
+                crud._key_getters_for_crud_column(compiler, stmt, compile_state)
+            _has_multi_parameters = compile_state._has_multi_parameters
+        elif SA_VERSION >= SA_1_1:
             _column_as_key, _getattr_col_key, _col_bind_name = \
                 crud._key_getters_for_crud_column(compiler, stmt)
+            _has_multi_parameters = stmt._has_multi_parameters
         else:
             _column_as_key, _getattr_col_key, _col_bind_name = \
                 crud._key_getters_for_crud_column(compiler)
+            _has_multi_parameters = stmt._has_multi_parameters
+
+        if _has_multi_parameters:
+            stmt_parameters = stmt.parameters[0]
+        else:
+            stmt_parameters = stmt.parameters
 
         # if we have statement parameters - set defaults in the
         # compiled params

src/crate/client/sqlalchemy/sa_version.py

@@ -25,3 +25,4 @@
 SA_VERSION = V(sa.__version__)
 
 SA_1_1 = V('1.1a0')
+SA_1_4 = V('1.4.0b1')