Automatic LIMIT clause

I'm currently evaluating ClickHouse, a new open source columnar RDBMS for "big data" and other analytics / data warehouse applications. One of the first thing I installed was of course its JDBC Driver to use it with DbVis.

But the DB and its JDBC driver really take throughput seriously: without a LIMIT clause, a SELECT will take forever, because the engine is preparing to stream GBs of data at you.

Unfortunately I could not find a way to configure DbVis so that it passes the row limit (Max Rows in the status bar) to the engine, in the form of a LIMIT clause at the end of the query.

I'm currently working around the issue by leaving Max Rows to -1 and writing LIMIT by hand in the Filter bar, but it's not as convenient.

Does DbVis provide an option to translate Max Rows into a LIMIT clause? If not, can you add it as a feature request? I see somebody else inquired about it 4 years ago for another DB, but I can't tell if anything has been done about it.

Hi Tobia,

As per the JDBC specification, the Statement#setMaxRows() method is the way to limit the number of rows a statement should return. It is up to the driver implementation to translate this into something the database supports, e.g. adding a LIMIT clause. I therefore urge you to ask the JDBC driver vendor to handle this in Statement#setMaxRows().

That said, we know of a few drivers with this problem and have an open ticket to see if we can work-around this at least for the special case of the query used by the Data tab. I'll add your vote.

Best Regards,

Hans

You are right of course. I've opened an issue on their GitHub repo (and will probably contribute a patch if nobody else solves it.)

Thanks