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pgasync

svcfmtm edited this page Feb 25, 2024 · 2 revisions

Async Data Flow

To avoid some performance issues, all communication with the database is async using the asyncpg module. If using the async model in SQLAlchemy, it uses asyncpg as well. Performance wise, depending on the actual operation, asyncpg may be faster than psycopg2 or not.

Initialization

When using asyncpg, the init() method in a class cannot have any calls to an async routine. This is because it's a constructor. This then requires two steps to initialize a class. The first one constructs an instantiation of the class, the following line then calls connect, whichfrom then on is fully async.

Defining methods

Each class must have async in front of the def if it is to call any async code. Since this gets messy really fast, I just make all the defs async to avoid confusion. For example:

async def importDB(self, table: str, ):

Calling A Method

To call any async method, you need to prefix it with await. I think of it this way, async def puts the task on a list, and await pulls it out. Nice and simple. For example:

data = await self.tmdb.execute(sql)

If you get an error message about coroutines, that means you forgot the await keyword.

sys:1: RuntimeWarning: coroutine 'TmAdminManage.createTable' was never awaited

Threading

Originally this propject was using concurrent.futures for threading, but has switched entirely to the asynio module using asychronis tasks instead of threads since everything is designed to work together.

All the code is heavily threaded. Data is split into chunks based on the number of CPU cores. Then each chunk is then handed off to an async Task to process the data. Since the threading is buried deep in this API, it shouldn't be needed in most applications using the TM-Admin API will need to do threading at a higher level for any of the data flow.

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