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*: improve NULL count estimation for single column index (#9474) #9979

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merged 6 commits into from
Apr 2, 2019
Merged

*: improve NULL count estimation for single column index (#9474) #9979

merged 6 commits into from
Apr 2, 2019

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eurekaka
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@eurekaka eurekaka commented Apr 1, 2019

cherry-pick #9474

@eurekaka eurekaka added type/enhancement The issue or PR belongs to an enhancement. sig/planner SIG: Planner type/2.1 cherry-pick labels Apr 1, 2019
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zz-jason commented Apr 2, 2019

@eurekaka build failed:

planner/core/planbuilder.go:657:5: undefined: idxNames
make: *** [server] Error 2
script returned exit code 2

eurekaka
eurekaka commented Apr 2, 2019
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planner/core/cbo_test.go
@@ -278,7 +278,7 @@ func (s *testAnalyzeSuite) TestIndexRead(c *C) {
},
{
sql: "select count(*) from t where e > 1 group by b",
best: "IndexLookUp(Index(t.b)[[NULL,+inf]], Table(t)->Sel([gt(test.t.e, 1)]))->StreamAgg",
best: "TableReader(Table(t)->Sel([gt(test.t.e, 1)])->HashAgg)->HashAgg",
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For reviewers: before this PR, column b is not analyzed because of the existence of index on b, so estimated NDV of b is about 8000; after this PR, estimated NDV of b is 100 which is consistent with data, and the plan is changed due to this NDV change.

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eurekaka commented Apr 2, 2019

/run-all-tests tidb-test=release-2.1 tikv=release-2.1 pd=release-2.1

@eurekaka eurekaka requested review from alivxxx and zz-jason April 2, 2019 08:19
alivxxx
alivxxx reviewed Apr 2, 2019
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LGTM

@alivxxx alivxxx added the status/LGT1 Indicates that a PR has LGTM 1. label Apr 2, 2019
zz-jason
zz-jason approved these changes Apr 2, 2019
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LGTM

@zz-jason zz-jason added status/LGT2 Indicates that a PR has LGTM 2. and removed status/LGT1 Indicates that a PR has LGTM 1. labels Apr 2, 2019
@zz-jason zz-jason merged commit 59eb553 into pingcap:release-2.1 Apr 2, 2019
@eurekaka eurekaka deleted the pick_null_estimation_2.1 branch April 2, 2019 12:14
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@zz-jason zz-jason zz-jason approved these changes

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@eurekaka @zz-jason @alivxxx