basic connection methods

Author: vgvoleg

ydb_dbapi/connection.py

@@ -1,15 +1,54 @@
+from typing import (
+    Any,
+    Optional,
+)
+
+import ydb
+
+
 class Connection:
-    def __init__(self):
-        pass
+    def __init__(
+        self,
+        host: str = "",
+        port: str = "",
+        database: str = "",
+        **conn_kwargs: Any,
+    ):
+        self.endpoint = f"grpc://{host}:{port}"
+        self.database = database
+        self.conn_kwargs = conn_kwargs
+        self.credentials = self.conn_kwargs.pop("credentials", None)
+        self.table_path_prefix = self.conn_kwargs.pop(
+            "ydb_table_path_prefix", ""
+        )
+
+        self.session_pool: ydb.aio.QuerySessionPool = None
+        self.session: ydb.aio.QuerySession = None
+        self.tx_context: Optional[ydb.QueryTxContext] = None
+        self.tx_mode: ydb.BaseQueryTxMode = ydb.QuerySerializableReadWrite()
 
     def cursor(self):
         pass
 
+    async def begin(self):
+        self.tx_context = None
+        self.session = await self.session_pool.acquire()
+        self.tx_context = self.session.transaction(self.tx_mode)
+        await self.tx_context.begin()
+
     async def commit(self):
-        pass
+        if self.tx_context and self.tx_context.tx_id:
+            await self.tx_context.commit()
+            await self.session_pool.release(self.session)
+            self.session = None
+            self.tx_context = None
 
     async def rollback(self):
-        pass
+        if self.tx_context and self.tx_context.tx_id:
+            await self.tx_context.rollback()
+            await self.session_pool.release(self.session)
+            self.session = None
+            self.tx_context = None
 
     async def close(self):
         pass