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https://issues.apache.org/jira/browse/CASSANDRA-847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12842152#action_12842152
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Jonathan Ellis commented on CASSANDRA-847:
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> I've always considered the Iterator interface to be super-weak for IO. There
> is no support for exception handling, and hasNext() is dangerous (when you
> begin chaining iterators that are returning lazy objects like IteratingRow)
> because it usually involves seeks.
Typed exceptions are a misfeature anyway, so that's a non-issue.
hasNext won't seek any more than a clunkier manual interface. either way you
need to (a) design your format so you don't have to do random i/o and (b)
buffer to avoid seeks when switching between different objects, and that is
what we do.
the old iterator-based compaction for instance never does more seeks than
another interface would given the same buffer sizes.
> Make the reading half of compactions memory-efficient
> -----------------------------------------------------
>
> Key: CASSANDRA-847
> URL: https://issues.apache.org/jira/browse/CASSANDRA-847
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Stu Hood
> Priority: Critical
> Fix For: 0.7
>
> Attachments:
> 0001-Add-structures-that-were-important-to-the-SSTableSca.patch,
> 0002-Implement-most-of-the-new-SSTableScanner-interface.patch,
> 0003-Rename-RowIndexedReader-specific-test.patch,
> 0004-Improve-Scanner-tests-and-separate-SuperCF-handling-.patch,
> 0005-Add-Scanner-interface-and-a-Filtered-implementation-.patch,
> 0006-Add-support-for-compaction-of-super-CFs-and-some-tes.patch
>
>
> This issue is the next on the road to finally fixing CASSANDRA-16. To make
> compactions memory efficient, we have to be able to perform the compaction
> process on the smallest possible chunks that might intersect and contend
> one-another, meaning that we need a better abstraction for reading from
> SSTables.
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