Merge "Support DEFAULT VALUES and VALUES(DEFAULT) individually"

11 files changed, 64 insertions, 4 deletions

diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py
index f45d5ec91..c5113b054 100644
--- a/lib/sqlalchemy/dialects/mysql/base.py
+++ b/lib/sqlalchemy/dialects/mysql/base.py
@@ -2534,6 +2534,11 @@ class MySQLDialect(default.DefaultDialect):
     supports_for_update_of = False  # default for MySQL ...
     # ... may be updated to True for MySQL 8+ in initialize()
 
+    # MySQL doesn't support "DEFAULT VALUES" but *does* support
+    # "VALUES (DEFAULT)"
+    supports_default_values = False
+    supports_default_metavalue = True
+
     supports_sane_rowcount = True
     supports_sane_multi_rowcount = False
     supports_multivalues_insert = True
diff --git a/lib/sqlalchemy/dialects/oracle/base.py b/lib/sqlalchemy/dialects/oracle/base.py
index 6496c4f71..3e1f50fc8 100644
--- a/lib/sqlalchemy/dialects/oracle/base.py
+++ b/lib/sqlalchemy/dialects/oracle/base.py
@@ -1453,7 +1453,11 @@ class OracleDialect(default.DefaultDialect):
     requires_name_normalize = True
 
     supports_comments = True
+
+    # Oracle supports these syntaxes but I'm not able to get them
+    # to work with RETURNING which we usually need
     supports_default_values = False
+    supports_default_metavalue = True
     supports_empty_insert = False
 
     statement_compiler = OracleCompiler
diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index 3b419ed16..0e9968031 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -3079,6 +3079,9 @@ class PGDialect(default.DefaultDialect):
 
     supports_comments = True
     supports_default_values = True
+
+    supports_default_metavalue = True
+
     supports_empty_insert = False
     supports_multivalues_insert = True
     default_paramstyle = "pyformat"
diff --git a/lib/sqlalchemy/dialects/sqlite/base.py b/lib/sqlalchemy/dialects/sqlite/base.py
index 28901d028..0075b3876 100644
--- a/lib/sqlalchemy/dialects/sqlite/base.py
+++ b/lib/sqlalchemy/dialects/sqlite/base.py
@@ -1791,7 +1791,12 @@ class SQLiteDialect(default.DefaultDialect):
     supports_alter = False
     supports_unicode_statements = True
     supports_unicode_binds = True
+
+    # SQlite supports "DEFAULT VALUES" but *does not* support
+    # "VALUES (DEFAULT)"
     supports_default_values = True
+    supports_default_metavalue = False
+
     supports_empty_insert = False
     supports_cast = True
     supports_multivalues_insert = True
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 375a93a48..a917228ad 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -141,8 +141,18 @@ class DefaultDialect(interfaces.Dialect):
     supports_sane_multi_rowcount = True
     colspecs = {}
     default_paramstyle = "named"
+
     supports_default_values = False
+    """dialect supports INSERT... DEFAULT VALUES syntax"""
+
+    supports_default_metavalue = False
+    """dialect supports INSERT... VALUES (DEFAULT) syntax"""
+
+    # not sure if this is a real thing but the compiler will deliver it
+    # if this is the only flag enabled.
     supports_empty_insert = True
+    """dialect supports INSERT () VALUES ()"""
+
     supports_multivalues_insert = False
 
     supports_is_distinct_from = True
diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 8eefa10d1..0c701cb52 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -3480,6 +3480,7 @@ class SQLCompiler(Compiled):
         if (
             not crud_params
             and not self.dialect.supports_default_values
+            and not self.dialect.supports_default_metavalue
             and not self.dialect.supports_empty_insert
         ):
             raise exc.CompileError(
diff --git a/lib/sqlalchemy/sql/crud.py b/lib/sqlalchemy/sql/crud.py
index 174a1c131..5fa82bcd0 100644
--- a/lib/sqlalchemy/sql/crud.py
+++ b/lib/sqlalchemy/sql/crud.py
@@ -174,7 +174,11 @@ def _get_crud_params(compiler, stmt, compile_state, **kw):
         values = _extend_values_for_multiparams(
             compiler, stmt, compile_state, values, kw
         )
-    elif not values and compiler.for_executemany:
+    elif (
+        not values
+        and compiler.for_executemany
+        and compiler.dialect.supports_default_metavalue
+    ):
         # convert an "INSERT DEFAULT VALUES"
         # into INSERT (firstcol) VALUES (DEFAULT) which can be turned
         # into an in-place multi values.  This supports
diff --git a/lib/sqlalchemy/testing/assertions.py b/lib/sqlalchemy/testing/assertions.py
index 02137474b..9ff2f76eb 100644
--- a/lib/sqlalchemy/testing/assertions.py
+++ b/lib/sqlalchemy/testing/assertions.py
@@ -400,6 +400,7 @@ class AssertsCompiledSQL(object):
         use_default_dialect=False,
         allow_dialect_select=False,
         supports_default_values=True,
+        supports_default_metavalue=True,
         literal_binds=False,
         render_postcompile=False,
         schema_translate_map=None,
@@ -410,6 +411,7 @@ class AssertsCompiledSQL(object):
         if use_default_dialect:
             dialect = default.DefaultDialect()
             dialect.supports_default_values = supports_default_values
+            dialect.supports_default_metavalue = supports_default_metavalue
         elif allow_dialect_select:
             dialect = None
         else:
@@ -421,6 +423,7 @@ class AssertsCompiledSQL(object):
             elif dialect == "default":
                 dialect = default.DefaultDialect()
                 dialect.supports_default_values = supports_default_values
+                dialect.supports_default_metavalue = supports_default_metavalue
             elif dialect == "default_enhanced":
                 dialect = default.StrCompileDialect()
             elif isinstance(dialect, util.string_types):
diff --git a/lib/sqlalchemy/testing/assertsql.py b/lib/sqlalchemy/testing/assertsql.py
index 1bdd11585..98261a374 100644
--- a/lib/sqlalchemy/testing/assertsql.py
+++ b/lib/sqlalchemy/testing/assertsql.py
@@ -76,7 +76,11 @@ class CompiledSQL(SQLMatchRule):
 
     def _compile_dialect(self, execute_observed):
         if self.dialect == "default":
-            return DefaultDialect()
+            dialect = DefaultDialect()
+            # this is currently what tests are expecting
+            # dialect.supports_default_values = True
+            dialect.supports_default_metavalue = True
+            return dialect
         else:
             # ugh
             if self.dialect == "postgresql":
diff --git a/lib/sqlalchemy/testing/requirements.py b/lib/sqlalchemy/testing/requirements.py
index f82d5f065..8a70cc692 100644
--- a/lib/sqlalchemy/testing/requirements.py
+++ b/lib/sqlalchemy/testing/requirements.py
@@ -335,11 +335,19 @@ class SuiteRequirements(Requirements):
 
         return exclusions.only_if(
             lambda config: config.db.dialect.supports_empty_insert
-            or config.db.dialect.supports_default_values,
+            or config.db.dialect.supports_default_values
+            or config.db.dialect.supports_default_metavalue,
             "empty inserts not supported",
         )
 
     @property
+    def empty_inserts_executemany(self):
+        """target platform supports INSERT with no values, i.e.
+        INSERT DEFAULT VALUES or equivalent, within executemany()"""
+
+        return self.empty_inserts
+
+    @property
     def insert_from_select(self):
         """target platform supports INSERT from a SELECT."""
 
diff --git a/lib/sqlalchemy/testing/suite/test_insert.py b/lib/sqlalchemy/testing/suite/test_insert.py
index 35f3315c7..3c033a774 100644
--- a/lib/sqlalchemy/testing/suite/test_insert.py
+++ b/lib/sqlalchemy/testing/suite/test_insert.py
@@ -167,8 +167,21 @@ class InsertBehaviorTest(fixtures.TablesTest):
                 self.tables.autoinc_pk.c.id != None
             )
         )
+        eq_(len(r.all()), 1)
 
-        assert len(r.fetchall())
+    @requirements.empty_inserts_executemany
+    def test_empty_insert_multiple(self, connection):
+        r = connection.execute(self.tables.autoinc_pk.insert(), [{}, {}, {}])
+        assert r._soft_closed
+        assert not r.closed
+
+        r = connection.execute(
+            self.tables.autoinc_pk.select().where(
+                self.tables.autoinc_pk.c.id != None
+            )
+        )
+
+        eq_(len(r.all()), 3)
 
     @requirements.insert_from_select
     def test_insert_from_select_autoinc(self, connection):