【ETCD】【源码阅读】深入解析 ETCD 线性一致性读请求处理流程（四）

本篇来详细分析方法Range(ctx context.Context, key, end []byte, ro RangeOptions) (r *RangeResult, err error)具体实现了哪些功能及其作用。

一、完整代码

func (tr *storeTxnRead) rangeKeys(ctx context.Context, key, end []byte, curRev int64, ro RangeOptions) (*RangeResult, error) {
   
	rev := ro.Rev
	if rev > curRev {
   
		return &RangeResult{
   KVs: nil, Count: -1, Rev: curRev}, ErrFutureRev
	}
	if rev <= 0 {
   
		rev = curRev
	}
	if rev < tr.s.compactMainRev {
   
		return &RangeResult{
   KVs: nil, Count: -1, Rev: 0}, ErrCompacted
	}
	if ro.Count {
   
		total := tr.s.kvindex.CountRevisions(key, end, rev)
		tr.trace.Step("count revisions from in-memory index tree")
		return &RangeResult{
   KVs: nil, Count: total, Rev: curRev}, nil
	}
	revpairs, total := tr.s.kvindex.Revisions(key, end, rev, int(ro.Limit))
	tr.trace.Step("range keys from in-memory index tree")
	if len(revpairs) == 0 {
   
		return &RangeResult{
   KVs: nil, Count: total, Rev: curRev}, nil
	}

	limit := int(ro.Limit)
	if limit <= 0