Add sequence support for MariaDB 10.3+.

Added support for use of the :class:`.Sequence` construct with MariaDB 10.3
and greater, as this is now supported by this database.  The construct
integrates with the :class:`.Table` object in the same way that it does for
other databases like PostrgreSQL and Oracle; if is present on the integer
primary key "autoincrement" column, it is used to generate defaults.   For
backwards compatibility, to support a :class:`.Table` that has a
:class:`.Sequence` on it to support sequence only databases like Oracle,
while still not having the sequence fire off for MariaDB, the optional=True
flag should be set, which indicates the sequence should only be used to
generate the primary key if the target database offers no other option.

Fixes: #4976
Closes: #4996
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/4996
Pull-request-sha: cb2e1426ea0b6bc6c93dbe8f033a11df9d8c4915

Change-Id: I507bc405eee6cae2c5991345d0eac53a37fe7512

1 files changed, 25 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/requirements.py b/lib/sqlalchemy/testing/requirements.py
index 5b26ac72e..8bbb7ec45 100644
--- a/lib/sqlalchemy/testing/requirements.py
+++ b/lib/sqlalchemy/testing/requirements.py
@@ -431,6 +431,13 @@ class SuiteRequirements(Requirements):
         )
 
     @property
+    def no_sequences(self):
+        """the oppopsite of "sequences", DB does not support sequences at
+        all."""
+
+        return exclusions.NotPredicate(self.sequences)
+
+    @property
     def sequences_optional(self):
         """Target database supports sequences, but also optionally
         as a means of generating new PK values."""
@@ -444,6 +451,24 @@ class SuiteRequirements(Requirements):
         )
 
     @property
+    def supports_lastrowid(self):
+        """target database / driver supports cursor.lastrowid as a means
+        of retrieving the last inserted primary key value.
+
+        note that if the target DB supports sequences also, this is still
+        assumed to work.  This is a new use case brought on by MariaDB 10.3.
+
+        """
+        return exclusions.only_if(
+            [lambda config: config.db.dialect.postfetch_lastrowid]
+        )
+
+    @property
+    def no_lastrowid_support(self):
+        """the opposite of supports_lastrowid"""
+        return exclusions.NotPredicate(self.supports_lastrowid)
+
+    @property
     def reflects_pk_names(self):
         return exclusions.closed()