Basic but working implementation of MySQL working copy

sno/sqlalchemy/create_engine.py

@@ -113,6 +113,30 @@ def _on_connect(psycopg2_conn, connection_record):
     return engine
 
 
+CANONICAL_MYSQL_SCHEME = "mysql"
+INTERNAL_MYSQL_SCHEME = "mysql+pymysql"
+
+
+def mysql_engine(msurl):
+    def _on_connect(mysql_conn, connection_record):
+        dbcur = mysql_conn.cursor()
+        dbcur.execute("SET time_zone='UTC';")
+        dbcur.execute("SET sql_mode = 'ANSI_QUOTES';")
+
+    url = urlsplit(msurl)
+    if url.scheme != CANONICAL_MYSQL_SCHEME:
+        raise ValueError("Expecting mysql://")
+    # url_query = _append_to_query(
+    #    url.query, {"Application Name": "sno"}
+    # )
+    msurl = urlunsplit([INTERNAL_MYSQL_SCHEME, url.netloc, url.path, url.query, ""])
+
+    engine = sqlalchemy.create_engine(msurl)
+    sqlalchemy.event.listen(engine, "connect", _on_connect)
+
+    return engine
+
+
 CANONICAL_SQL_SERVER_SCHEME = "mssql"
 INTERNAL_SQL_SERVER_SCHEME = "mssql+pyodbc"
 SQL_SERVER_INSTALL_DOC_URL = (

sno/sqlalchemy/upsert.py

@@ -67,6 +67,39 @@ def compile_upsert_postgresql(upsert_stmt, compiler, **kwargs):
     return compiler.process(insert_stmt)
 
 
+@compiles(Upsert, "mysql")
+def compile_upsert_mysql(upsert_stmt, compiler, **kwargs):
+    # See https://dev.mysql.com/doc/refman/8.0/en/insert-on-duplicate.html
+    preparer = compiler.preparer
+
+    def list_cols(col_names, prefix=""):
+        return ", ".join([prefix + c for c in col_names])
+
+    values = ", ".join(upsert_stmt.values(compiler))
+    table = preparer.format_table(upsert_stmt.table)
+    all_columns = [preparer.quote(c.name) for c in upsert_stmt.columns]
+    non_pk_columns = [preparer.quote(c.name) for c in upsert_stmt.non_pk_columns]
+
+    is_gte_version_8 = compiler.dialect.server_version_info[0] >= 8
+
+    if is_gte_version_8:
+        # Post 8.0 - don't use VALUES() again to refer to earlier VALUES.
+        # Instead, alias them. See https://dev.mysql.com/worklog/task/?id=13325
+        result = f"INSERT INTO {table} ({list_cols(all_columns)}) "
+        result += f" VALUES ({values}) AS SOURCE ({list_cols(all_columns)})"
+        result += " ON DUPLICATE KEY UPDATE "
+        result += ", ".join([f"{c} = SOURCE.{c}" for c in non_pk_columns])
+
+    else:
+        # Pre 8.0 - reuse VALUES to refer to earlier VALUES.
+        result = f"INSERT INTO {table} ({list_cols(all_columns)}) "
+        result += f" VALUES ({values})"
+        result += " ON DUPLICATE KEY UPDATE "
+        result += ", ".join([f"{c} = VALUES({c})" for c in non_pk_columns])  # 5.7
+
+    return result
+
+
 @compiles(Upsert, "mssql")
 def compile_upsert_mssql(upsert_stmt, compiler, **kwargs):
     # See https://docs.microsoft.com/sql/t-sql/statements/merge-transact-sql

sno/working_copy/__init__.py

@@ -9,6 +9,7 @@ class WorkingCopyType(Enum):
     GPKG = auto()
     POSTGIS = auto()
     SQL_SERVER = auto()
+    MYSQL = auto()
 
     @classmethod
     def from_location(cls, location, allow_invalid=False):
@@ -17,6 +18,8 @@ def from_location(cls, location, allow_invalid=False):
             return WorkingCopyType.POSTGIS
         elif location.startswith("mssql:"):
             return WorkingCopyType.SQL_SERVER
+        elif location.startswith("mysql:"):
+            return WorkingCopyType.MYSQL
         elif location.lower().endswith(".gpkg"):
             return WorkingCopyType.GPKG
         elif allow_invalid:
@@ -27,7 +30,8 @@ def from_location(cls, location, allow_invalid=False):
                 "Try one of:\n"
                 "  PATH.gpkg\n"
                 "  postgresql://[HOST]/DBNAME/DBSCHEMA\n"
-                "  mssql://[HOST]/DBNAME/DBSCHEMA"
+                "  mssql://[HOST]/DBNAME/DBSCHEMA\n"
+                "  mysql://[HOST]/DBNAME"
             )
 
     @property
@@ -44,6 +48,11 @@ def class_(self):
             from .sqlserver import WorkingCopy_SqlServer
 
             return WorkingCopy_SqlServer
+        elif self is WorkingCopyType.MYSQL:
+            from .mysql import WorkingCopy_MySql
+
+            return WorkingCopy_MySql
+
         raise RuntimeError("Invalid WorkingCopyType")