Re: What's the '--quick' meaning in mysqldump?

[Rick James]

Yeah, "quick" is a confusing option. Here's an explanation of the two methods that can be used for a SELECT. Note: mysqldump is effectively doing SELECTs to fetch the data.

Plan A:
Ask the server for all the rows, collect them in a buffer in mysqldump, then write them to the output file.

Plan B:
Ask the server for the rows a few at a time, as they arrive, write them to output.

Generally, you can't tell the difference between these two schemes.

For small, or even medium sized tables, it does not matter.

For tables with many millions of rows:
Plan A could run out of RAM.
Plan B would start writing sooner, but might (or might not) take longer to finish.

I think the confusion has to do with which part it "quick". A better term would be "stream" or "buffer" or something closer to what it is doing.