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From Robert Buck <>
Subject Newbie question: compaction and mvcc consistency?
Date Wed, 26 May 2010 18:37:18 GMT
Here is a newbie question for you that relates MVCC, compaction, and versioning.

I read that old versions of documents are cleaned up upon compaction.
I read that every b-tree root will point to a consistent snapshot of
the database.
I read that there could be readers reading three different versions
[of a document] at the same time [due to timing of reads vs writes].

So long as reader (i) is reading a document (r), if updates to the
document introduce an effective change from r->s, if after 's' has
been added the database were compacted, what would reader (i) see?
Would document (r) be pulled out from under reader (i) or would the
document remain until such time as the reader no longer refers to it?


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