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hard link #77

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yvxiang opened this issue Aug 24, 2015 · 4 comments
Closed

hard link #77

yvxiang opened this issue Aug 24, 2015 · 4 comments

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@yvxiang
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yvxiang commented Aug 24, 2015

我看到levelDB-split中分裂tablet时，对原sst文件做了硬链接操作，然后去构造manifest。dfs有没有必要支持硬链接？
@bluebore
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这个和 @xupeilin 讨论过，硬链接没有高效的实现，比如我要对一个db做硬链接，只能遍历所有文件，逐个处理。

@yvxiang
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yvxiang commented Aug 25, 2015

刚扫了一下目前tera中的实现，如果我没理解错的话，应该是找出splitkey，然后修改元数据表，但实际上leveldb并没有作改动？
而另一种方案是既修改tera中的元数据表，又修改leveldb中的manifest。
相对于第一种方案来讲，第二种方案的优势在于什么？因为也是相当于只修改的元数据，但是sst文件中的元数据并没有变化，查找某个kv对时，仍然先需要在整个sst文件的block元信息中进行查找（不知道这里我对leveldb的理解对不对……目前正在读其源码）

@bluebore
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没发现第二种有什么优势，既然修改元数据就可以了，就没必要修改manifest了
毕竟修改manifest这个操作，很难做到原子的

@yvxiang
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yvxiang commented Aug 25, 2015

了解~

@yvxiang yvxiang closed this as completed Aug 25, 2015
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@yvxiang @bluebore