statistics: prioritize low selectivity indexes in ... (#20038) (#20154)

pingcap · Oct 3, 2020 · 928d9fa · 928d9fa
1 parent 81388ab
commit 928d9fa
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Showing 5 changed files with 99,430 additions and 3 deletions.
diff --git a/planner/core/cbo_test.go b/planner/core/cbo_test.go
@@ -805,6 +805,38 @@ func (s *testAnalyzeSuite) TestLimitCrossEstimation(c *C) {
 	}
 }
 
+func (s *testAnalyzeSuite) TestLowSelIndexGreedySearch(c *C) {
+	defer testleak.AfterTest(c)()
+	store, dom, err := newStoreWithBootstrap()
+	c.Assert(err, IsNil)
+	testKit := testkit.NewTestKit(c, store)
+	defer func() {
+		dom.Close()
+		store.Close()
+	}()
+	testKit.MustExec("use test")
+	testKit.MustExec("drop table if exists t")
+	testKit.MustExec("create table t (a varchar(32) default null, b varchar(10) default null, c varchar(12) default null, d varchar(32) default null, e bigint(10) default null, key idx1 (d,a), key idx2 (a,c), key idx3 (c,b), key idx4 (e))")
+	err = s.loadTableStats("analyzeSuiteTestLowSelIndexGreedySearchT.json", dom)
+	c.Assert(err, IsNil)
+	var input []string
+	var output []struct {
+		SQL  string
+		Plan []string
+	}
+	// The test purposes are:
+	// - index `idx2` runs much faster than `idx4` experimentally;
+	// - estimated row count of IndexLookUp should be 0;
+	s.testData.GetTestCases(c, &input, &output)
+	for i, tt := range input {
+		s.testData.OnRecord(func() {
+			output[i].SQL = tt
+			output[i].Plan = s.testData.ConvertRowsToStrings(testKit.MustQuery(tt).Rows())
+		})
+		testKit.MustQuery(tt).Check(testkit.Rows(output[i].Plan...))
+	}
+}
+
 func (s *testAnalyzeSuite) TestUpdateProjEliminate(c *C) {
 	store, dom, err := newStoreWithBootstrap()
 	c.Assert(err, IsNil)