long totalSize = 0;
if (!majorcompaction && !references) {
// we're doing a minor compaction, let's see what files are applicable
int start = 0;
double r = this.compactRatio;
/* Start at the oldest file and stop when you find the first file that
* meets compaction criteria:
* 从老的storefile到新的storefile进行遍历，停止的条件是当遇到一个storefile的
* 大小小于minCompactSize的时候，或者是小于后面maxFilesToCompact个storefile
* 大小的和乘以compactRatio（默认1.2）
*
* X <= minCompactSize || X <= SUM_ * compactRatio ==> 停止
* X > minCompactSize && x > SUM_ * compactRation ==> 继续扫描
* X > max(minCompactSize, SUM_ * compactRation) ==> 继续扫描
* (1) a recently-flushed, small file (i.e. <= minCompactSize)
* OR
* (2) within the compactRatio of sum(newer_files)
* Given normal skew, any newer files will also meet this criteria
*
* Additional Note:
* If fileSizes.size() >> maxFilesToCompact, we will recurse on
* compact(). Consider the oldest files first to avoid a
* situation where we always compact [end-threshold,end). Then, the
* last file becomes an aggregate of the previous compactions.
*/
/*
* 至少有compactionThreshold这么多个store files
* 至少满足停止条件（1）（2）的时候
* ==>
* 才能进行min compaction
*/
while(countOfFiles - start >= this.compactionThreshold &&
fileSizes[start] >
Math.max(minCompactSize, (long)(sumSize[start+1] * r))) {
++start;
}
// 确定我们一次min compaction最多只能有maxFilesToCompact个store file
int end = Math.min(countOfFiles, start + this.maxFilesToCompact);
// 包含在这次min compaction里面的store file总大小
totalSize = fileSizes[start]
+ ((start+1 < countOfFiles) ? sumSize[start+1] : 0);