MonetDBe-Python 可以使用 COPY 命令吗？

Question

I was having some trouble bulk-loading records to go faster than what cursor.executemany would allow. I hoped the bulk operations documented with regular MonetDB here might work, so I tried an export as a test. eg cursor.execute("COPY SELECT * FROM foo INTO '/file/path.csv'") . This doesn't raise an error unless the file already exists, but the resulting file is always 0 bytes. I tried the same with file STDOUT and it prints nothing.

Are these COPY commands meant to work on the embedded version?

Note: This is my first use of anything related to MonetDB. As a fan of SQLite and a not-super-impressed user of Amazon Redshift, this seemed like a neat project. Not sure if MonetDB/e is the same as MonetDBLite - the former seems more active lately?

Answer 1

Exporting data through a COPY INTO command should be possible in MonetDB/e, yes.

However, this feature is not working currently. I was able to reproduce your problem, ie the COPY INTO creates the file where the data should be exported to, but doesn't write the data. This does not happen with regular MonetDB.

Our team is notified of this issue, and we're looking into it. Thanks for the heads up!

PS: Regarding your doubt about MonetDB/e vs MonetDBLite: our team no long develops and maintains MonetDBLite. Both are embedded databases that use MonetDB as the core engine, but MonetDBLite is deprecated. After having learnt some do's and don'ts with MonetDBLite, our team is developing our next generation of embedded databases.

So for your embedded database needs, you should follow what's coming out of our MonetDB/e projects.

Answer 2

I've created a test for it at: https://github.com/MonetDBSolutions/monetdbe-examples/blob/CI/C/copy_into.c

Also filed a bug report over on GitHub: https://github.com/MonetDB/MonetDB/issues/7058

We're currently looking into this issue.