Can tqdm be used with Database Reads?

问题

While reading large relations from a SQL database to a pandas dataframe, it would be nice to have a progress bar, because the number of tuples is known statically and the I/O rate could be estimated. It looks like the tqdm module has a function tqdm_pandas which will report progress on mapping functions over columns, but by default calling it does not have the effect of reporting progress on I/O like this. Is it possible to use tqdm to make a progress bar on a call to pd.read_sql?

回答1:

Edit: Answer may be misleading - chunksize has no effect on database side of the operation. See comments below.

You could use the chunksize parameter to do something like this:

chunks = pd.read_sql('SELECT * FROM table', con=conn, chunksize=100)

df = pd.DataFrame()
for chunk in tqdm(chunks):
    df = pd.concat([df, chunk])

I think this would use less memory as well.

来源：https://stackoverflow.com/questions/40282478/can-tqdm-be-used-with-database-reads