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executor: copy row data instead of refereeing chunk.Row in some window functions. (#11678) #11823

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merged 5 commits into from
Aug 22, 2019

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@sre-bot sre-bot commented Aug 22, 2019

cherry-pick #11678 to release-3.0


What problem does this PR solve?

Fixes #11614, and fixes #11626 .
If a chunk.Chunk reuse into a window function executor, it may break the internal memory reference in function RANK or PERCENT_RANK.

  1. Father calls chk := NewChunk()
  2. Father calls windowExecutor.Next(chk)
  3. The windowExecutor put column results into chk while refereeing the chunk.Row into PartialResult of function RANK or PERCENT_RANK.
  4. Father calls windowExecutor.Next(chk) again to collect next batch of result and reuses the same chk.
  5. chunk.Row refereced by PartialResult is broken when chk.Reset is called.
  • TODO: fix the other window functions which may lead this problem.

What is changed and how it works?

Change step 3 above, copy row data instead of refereeing chunk.Row in window functions which rely on data comparing.

Check List

Tests

  • Unit test

Code changes

  • None

Side effects

  • Possible performance regression
  • note: no func lag because it cannot be finished with old code.
name                                                           old time/op    new time/op    delta
WindowRows/(func:row_number,_ndv:10,_rows:1000)-12               65.7µs ± 9%    68.5µs ± 8%       ~     (p=0.523 n=3+3)
WindowRows/(func:row_number,_ndv:1000,_rows:1000)-12              131µs ± 2%     161µs ± 8%    +22.55%  (p=0.041 n=3+3)
WindowRows/(func:row_number,_ndv:10,_rows:100000)-12             5.98ms ± 1%    5.97ms ± 1%       ~     (p=0.784 n=3+3)
WindowRows/(func:row_number,_ndv:1000,_rows:100000)-12           6.19ms ± 2%    6.07ms ± 0%       ~     (p=0.173 n=3+3)
WindowFunctions/(func:row_number,_ndv:1000,_rows:100000)-12      6.07ms ± 2%    6.06ms ± 3%       ~     (p=0.942 n=3+3)
WindowFunctions/(func:rank,_ndv:1000,_rows:100000)-12            6.79ms ± 0%    9.61ms ± 1%    +41.60%  (p=0.000 n=3+3)
WindowFunctions/(func:dense_rank,_ndv:1000,_rows:100000)-12      6.81ms ± 1%    9.70ms ± 1%    +42.59%  (p=0.000 n=3+3)
WindowFunctions/(func:cume_dist,_ndv:1000,_rows:100000)-12       6.82ms ± 3%   10.09ms ± 1%    +47.99%  (p=0.000 n=3+3)
WindowFunctions/(func:percent_rank,_ndv:1000,_rows:100000)-12    6.86ms ± 1%    9.62ms ± 0%    +40.25%  (p=0.000 n=3+3)
WindowFunctions/(func:ntile,_ndv:1000,_rows:100000)-12           6.31ms ± 1%    6.17ms ± 1%       ~     (p=0.050 n=3+3)
WindowFunctions/(func:lead,_ndv:1000,_rows:100000)-12            8.04ms ± 1%   12.30ms ± 0%    +52.91%  (p=0.000 n=3+3)
WindowFunctions/(func:first_value,_ndv:1000,_rows:100000)-12     6.28ms ± 1%    6.44ms ± 0%       ~     (p=0.063 n=3+3)
WindowFunctions/(func:last_value,_ndv:1000,_rows:100000)-12      6.36ms ± 0%    6.40ms ± 1%       ~     (p=0.415 n=3+3)
WindowFunctions/(func:nth_value,_ndv:1000,_rows:100000)-12       6.48ms ± 1%    6.47ms ± 1%       ~     (p=0.871 n=3+3)

name                                                           old alloc/op   new alloc/op   delta
WindowRows/(func:row_number,_ndv:10,_rows:1000)-12               44.7kB ± 0%    44.7kB ± 0%       ~     (zero variance)
WindowRows/(func:row_number,_ndv:1000,_rows:1000)-12             81.0kB ± 1%    80.5kB ± 1%       ~     (p=0.523 n=3+3)
WindowRows/(func:row_number,_ndv:10,_rows:100000)-12              263kB ± 0%     263kB ± 0%       ~     (p=0.443 n=3+3)
WindowRows/(func:row_number,_ndv:1000,_rows:100000)-12            301kB ± 0%     299kB ± 1%       ~     (p=0.423 n=3+3)
WindowFunctions/(func:row_number,_ndv:1000,_rows:100000)-12       301kB ± 0%     301kB ± 0%       ~     (zero variance)
WindowFunctions/(func:rank,_ndv:1000,_rows:100000)-12             307kB ± 0%    6917kB ± 0%  +2155.27%  (p=0.000 n=3+3)
WindowFunctions/(func:dense_rank,_ndv:1000,_rows:100000)-12       306kB ± 0%    6921kB ± 0%  +2160.67%  (p=0.000 n=3+3)
WindowFunctions/(func:cume_dist,_ndv:1000,_rows:100000)-12        306kB ± 0%    6923kB ± 0%  +2161.01%  (p=0.000 n=3+3)
WindowFunctions/(func:percent_rank,_ndv:1000,_rows:100000)-12     306kB ± 0%    6929kB ± 0%  +2162.99%  (p=0.000 n=3+3)
WindowFunctions/(func:ntile,_ndv:1000,_rows:100000)-12            307kB ± 0%     301kB ± 0%     -1.95%  (p=0.000 n=3+3)
WindowFunctions/(func:lead,_ndv:1000,_rows:100000)-12             306kB ± 0%    5984kB ± 0%  +1857.22%  (p=0.000 n=3+3)
WindowFunctions/(func:first_value,_ndv:1000,_rows:100000)-12      301kB ± 0%     301kB ± 0%       ~     (zero variance)
WindowFunctions/(func:last_value,_ndv:1000,_rows:100000)-12       301kB ± 0%     301kB ± 0%       ~     (zero variance)
WindowFunctions/(func:nth_value,_ndv:1000,_rows:100000)-12        301kB ± 0%     301kB ± 0%       ~     (zero variance)

name                                                           old allocs/op  new allocs/op  delta
WindowRows/(func:row_number,_ndv:10,_rows:1000)-12                 74.0 ± 0%      74.0 ± 0%       ~     (zero variance)
WindowRows/(func:row_number,_ndv:1000,_rows:1000)-12                698 ± 3%       690 ± 1%       ~     (p=0.523 n=3+3)
WindowRows/(func:row_number,_ndv:10,_rows:100000)-12              1.94k ± 0%     1.94k ± 0%       ~     (p=1.000 n=3+3)
WindowRows/(func:row_number,_ndv:1000,_rows:100000)-12            3.00k ± 0%     3.00k ± 0%       ~     (p=0.423 n=3+3)
WindowFunctions/(func:row_number,_ndv:1000,_rows:100000)-12       3.00k ± 0%     3.00k ± 0%       ~     (zero variance)
WindowFunctions/(func:rank,_ndv:1000,_rows:100000)-12             3.01k ± 0%    23.81k ± 0%   +691.91%  (p=0.000 n=3+3)
WindowFunctions/(func:dense_rank,_ndv:1000,_rows:100000)-12       3.01k ± 0%    23.83k ± 0%   +692.33%  (p=0.000 n=3+3)
WindowFunctions/(func:cume_dist,_ndv:1000,_rows:100000)-12        3.01k ± 0%    23.83k ± 0%   +692.54%  (p=0.000 n=3+3)
WindowFunctions/(func:percent_rank,_ndv:1000,_rows:100000)-12     3.01k ± 0%    23.85k ± 0%   +693.17%  (p=0.000 n=3+3)
WindowFunctions/(func:ntile,_ndv:1000,_rows:100000)-12            3.01k ± 0%     3.00k ± 0%       ~     (zero variance)
WindowFunctions/(func:lead,_ndv:1000,_rows:100000)-12             3.01k ± 0%   111.01k ± 0%  +3591.58%  (p=0.000 n=3+3)
WindowFunctions/(func:first_value,_ndv:1000,_rows:100000)-12      3.00k ± 0%     3.00k ± 0%       ~     (zero variance)
WindowFunctions/(func:last_value,_ndv:1000,_rows:100000)-12       3.00k ± 0%     3.00k ± 0%       ~     (zero variance)
WindowFunctions/(func:nth_value,_ndv:1000,_rows:100000)-12        3.00k ± 0%     3.00k ± 0%       ~     (zero variance)

Related changes

  • Need to cherry-pick to the release branch

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sre-bot commented Aug 22, 2019

/run-all-tests

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LGTM

@zz-jason zz-jason added the status/LGT1 Indicates that a PR has LGTM 1. label Aug 22, 2019
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LGTM

@zz-jason zz-jason merged commit 2fcfc73 into pingcap:release-3.0 Aug 22, 2019
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