planner: fix incorrect results when using a prefix index with OR condition (#21251)

util/ranger/detacher.go

@@ -317,6 +317,10 @@ func detachDNFCondAndBuildRangeForIndex(sctx sessionctx.Context, condition *expr
 		}
 	}
 
+	// Take prefix index into consideration.
+	if hasPrefix(lengths) {
+		fixPrefixColRange(totalRanges, lengths, newTpSlice)
+	}
 	totalRanges, err := UnionRanges(sc, totalRanges)
 	if err != nil {
 		return nil, nil, false, errors.Trace(err)

util/ranger/ranger_test.go

@@ -1200,6 +1200,42 @@ func (s *testRangerSuite) TestIndexStringIsTrueRange(c *C) {
 	}
 }
 
+func (s *testRangerSuite) TestPrefixIndexMultiColDNF(c *C) {
+	defer testleak.AfterTest(c)()
+	dom, store, err := newDomainStoreWithBootstrap(c)
+	defer func() {
+		dom.Close()
+		store.Close()
+	}()
+	c.Assert(err, IsNil)
+	testKit := testkit.NewTestKit(c, store)
+	testKit.MustExec("use test;")
+	testKit.MustExec("drop table if exists t2;")
+	testKit.MustExec("create table t2 (id int unsigned not null auto_increment primary key, t text, index(t(3)));")
+	testKit.MustExec("insert into t2 (t) values ('aaaa'),('a');")
+
+	var input []string
+	var output []struct {
+		SQL    string
+		Plan   []string
+		Result []string
+	}
+	s.testData.GetTestCases(c, &input, &output)
+	inputLen := len(input)
+	for i, tt := range input {
+		s.testData.OnRecord(func() {
+			output[i].SQL = tt
+			output[i].Plan = s.testData.ConvertRowsToStrings(testKit.MustQuery("explain " + tt).Rows())
+			output[i].Result = s.testData.ConvertRowsToStrings(testKit.MustQuery(tt).Rows())
+		})
+		testKit.MustQuery("explain " + tt).Check(testkit.Rows(output[i].Plan...))
+		testKit.MustQuery(tt).Check(testkit.Rows(output[i].Result...))
+		if i+1 == inputLen/2 {
+			testKit.MustExec("analyze table t2;")
+		}
+	}
+}
+
 func (s *testRangerSuite) TestIndexRangeForYear(c *C) {
 	defer testleak.AfterTest(c)()
 	dom, store, err := newDomainStoreWithBootstrap(c)

util/ranger/testdata/ranger_suite_in.json

@@ -17,5 +17,14 @@
       "explain select * from t0 where c0 and c0 in ('123','456','789')",
       "explain SELECT * FROM t0 WHERE ('a' != t0.c0) AND t0.c0;"
     ]
+  },
+  {
+    "name": "TestPrefixIndexMultiColDNF",
+    "cases": [
+      "select * from t2 where t='aaaa';",
+      "select * from t2 where t='aaaa' or t = 'a';",
+      "select * from t2 where t='aaaa';",
+      "select * from t2 where t='aaaa' or t = 'a';"
+    ]
   }
 ]

util/ranger/testdata/ranger_suite_out.json

@@ -86,5 +86,58 @@
         ]
       }
     ]
+  },
+  {
+    "Name": "TestPrefixIndexMultiColDNF",
+    "Cases": [
+      {
+        "SQL": "select * from t2 where t='aaaa';",
+        "Plan": [
+          "IndexLookUp_11 10.00 root  ",
+          "├─IndexRangeScan_8(Build) 10.00 cop[tikv] table:t2, index:t(t) range:[\"aaa\",\"aaa\"], keep order:false, stats:pseudo",
+          "└─Selection_10(Probe) 10.00 cop[tikv]  eq(test.t2.t, \"aaaa\")",
+          "  └─TableRowIDScan_9 10.00 cop[tikv] table:t2 keep order:false, stats:pseudo"
+        ],
+        "Result": [
+          "1 aaaa"
+        ]
+      },
+      {
+        "SQL": "select * from t2 where t='aaaa' or t = 'a';",
+        "Plan": [
+          "IndexLookUp_11 16.00 root  ",
+          "├─IndexRangeScan_8(Build) 20.00 cop[tikv] table:t2, index:t(t) range:[\"a\",\"a\"], [\"aaa\",\"aaa\"], keep order:false, stats:pseudo",
+          "└─Selection_10(Probe) 16.00 cop[tikv]  or(eq(test.t2.t, \"aaaa\"), eq(test.t2.t, \"a\"))",
+          "  └─TableRowIDScan_9 20.00 cop[tikv] table:t2 keep order:false, stats:pseudo"
+        ],
+        "Result": [
+          "1 aaaa",
+          "2 a"
+        ]
+      },
+      {
+        "SQL": "select * from t2 where t='aaaa';",
+        "Plan": [
+          "TableReader_7 1.00 root  data:Selection_6",
+          "└─Selection_6 1.00 cop[tikv]  eq(test.t2.t, \"aaaa\")",
+          "  └─TableRangeScan_5 2.00 cop[tikv] table:t2 range:[0,+inf], keep order:false"
+        ],
+        "Result": [
+          "1 aaaa"
+        ]
+      },
+      {
+        "SQL": "select * from t2 where t='aaaa' or t = 'a';",
+        "Plan": [
+          "TableReader_7 1.60 root  data:Selection_6",
+          "└─Selection_6 1.60 cop[tikv]  or(eq(test.t2.t, \"aaaa\"), eq(test.t2.t, \"a\"))",
+          "  └─TableRangeScan_5 2.00 cop[tikv] table:t2 range:[0,+inf], keep order:false"
+        ],
+        "Result": [
+          "1 aaaa",
+          "2 a"
+        ]
+      }
+    ]
   }
 ]