Tim Armstrong has posted comments on this change.

Change subject: IMPALA-3344: Simplify sorter and document/enforce invariants.
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Patch Set 7:

(7 comments)

Got partway through addressing the changes, but I was thinking that the 
complication in SortedRunMerger stems from the need_to_return() case. If 
resources are attached to the batches, we just need to make sure that resources 
are transferred if we get a 0-row batch.

We're planning to deprecate need_to_return and move to always explicitly 
transferring resources, so there isn't really much point to fixing this case.

How about I just document that deep_copy_input_ must be true if the 
BatchRunSupplierFn can return batches with the need_to_return flag set. Then I 
can add a DCHECK to assert this. I think then the resource management will be 
essentially correct.

http://gerrit.cloudera.org:8080/#/c/2826/7/be/src/runtime/sorted-run-merger.h
File be/src/runtime/sorted-run-merger.h:

Line 46: must
> I don't think 'must' makes sense
Done


Line 48: RunBatchSupplier
> Can we rename this to RunBatchSupplierFn? I find it confusing with BatchedR
Done


http://gerrit.cloudera.org:8080/#/c/2826/7/be/src/runtime/sorter.cc
File be/src/runtime/sorter.cc:

Line 66: Runs are either "initial runs" constructed from the sorter's input or 
"intermediate
       : /// runs" constructed by merging already-sorted runs. The input rows 
are materialized
       : /// into sort tuples in the initial runs using the expressions in
       : /// 'sort_tuple_slot_expr_ctxs_'.
> It feels like this should be woven in with the paragraph above it where we 
Done


Line 184: return
> Awkward verb conjugation throughout this sentence.
Done


Line 185: add
> adds
Done


Line 974: right
> right?
run. oops.


Line 993: TupleIterator
> what do you think about having a begin() and end() static constructor? (It 
Done


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Gerrit-MessageType: comment
Gerrit-Change-Id: I9c619e81fd1b8ac50e257172c8bce101a112b52a
Gerrit-PatchSet: 7
Gerrit-Project: Impala
Gerrit-Branch: cdh5-trunk
Gerrit-Owner: Tim Armstrong <[email protected]>
Gerrit-Reviewer: Dan Hecht <[email protected]>
Gerrit-Reviewer: Matthew Jacobs <[email protected]>
Gerrit-Reviewer: Tim Armstrong <[email protected]>
Gerrit-HasComments: Yes

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