Right, you got it.
You can change the maxVersions many times but that won't be persisted on
disk until a compaction rewrites that data. Scans will, however, always
be consistent with the current configuration.
In the implementation, Accumulo will instantiate the current iterators
for the minc or majc scope (depending on if it's a minor or major
compaction) and write the output of memory/files being compacted,
filtered/transformed by those iterators, back out to a single file.
z11373 wrote:
Thanks Josh for the answers. I just have one clarification from the answer
for #2.
So let say we set the max version to keep is default value (in this case is
1), then after few inserts with same key, and we change the max version to
3. Based on what you said, if the compaction occurs before we change to 3,
then we'll only see 1 row from scan (since all previous versions have been
deleted), is that correct?
If this is confirmed, then it looks like Accumulo is looking for that max
version to keep value while doing compaction, so that it knows how many of
previous versions need to be deleted, right?
Thanks,
Z
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