A misunderstanding literal errors
use filesort sort, literally an external sort.
Myth parrot
On Baidu more than we are not negative external sort that keyword and file it does not matter. Using a quick sort. But always felt impossible for so called filesort no reason, so check the next Quguan network.
Correct
Sure enough, I think that's only half are two positive solutions above all, use filesort are sorted in memory, but if the result set is too large to use an external memory will be used to sort. ( No matter what sort filesort are bottom with extra sorting, but faster than external memory sort sort that need to optimize sql friends ~ , here only explore filesort principle )
verification
Download Source mysql
Direct access github address https://github.com/mysql/mysql-server/ be downloaded or viewed directly
Quguan network can also be downloaded, and download mysql packages, not to say, just choose Operating System Source Code Select the final step in
View source
Initiate ~ ~ ~ ~ wave analysis by the Honorable Gangster (quietly tell you, I simply can not find the file in which to sort c ...)
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