planner: notify skyline pruning of index statistics availability (pin…

…gcap#59110)

close pingcap#57948

pkg/planner/cardinality/selectivity_test.go

@@ -349,7 +349,7 @@ func TestNewIndexWithoutStats(t *testing.T) {
 	testKit := testkit.NewTestKit(t, store)
 	testKit.MustExec("use test")
 	testKit.MustExec("drop table if exists t")
-	testKit.MustExec("create table t(a int, b int, c int, index idxa(a))")
+	testKit.MustExec("create table t(a int, b int, c int, index idxa(a), index idxca(c,a))")
 	testKit.MustExec("set @@tidb_analyze_version=2")
 	testKit.MustExec("set @@global.tidb_enable_auto_analyze='OFF'")
 	testKit.MustExec("insert into t values (1, 1, 1)")
@@ -364,6 +364,11 @@ func TestNewIndexWithoutStats(t *testing.T) {
 	testKit.MustExec("create index idxab on t(a, b)")
 	// New index idxab should win due to having the most matching equal predicates - regardless of no statistics
 	testKit.MustQuery("explain format='brief' select * from t where a = 5 and b = 5").CheckContain("idxab(a, b)")
+	// New index idxab should win due to having the most predicates - regardless of no statistics
+	testKit.MustQuery("explain format='brief' select * from t where a > 5 and b > 5").CheckContain("idxab(a, b)")
+	testKit.MustQuery("explain format='brief' select * from t where a = 5 and b > 5 and c > 5").CheckContain("idxab(a, b)")
+	// New index idxab should NOT win because idxca has the same number of equals and has statistics
+	testKit.MustQuery("explain format='brief' select * from t where a = 5 and b > 5 and c = 5").CheckContain("idxca(c, a)")
 }
 
 func TestIssue57948(t *testing.T) {

pkg/planner/core/find_best_task.go

@@ -760,23 +760,23 @@ func compareCandidates(sctx base.PlanContext, statsTbl *statistics.Table, tableI
 		// has the same or higher number of equal/IN predicates.
 		if !lhsPseudo && globalResult >= 0 && sum >= 0 &&
 			lhs.path.EqOrInCondCount > 0 && lhs.path.EqOrInCondCount >= rhs.path.EqOrInCondCount {
-			return 1, false // left wins and has statistics
+			return 1, lhsPseudo // left wins and has statistics (lhsPseudo==false)
 		}
 		if !rhsPseudo && globalResult <= 0 && sum <= 0 &&
 			rhs.path.EqOrInCondCount > 0 && rhs.path.EqOrInCondCount >= lhs.path.EqOrInCondCount {
-			return -1, false // right wins and has statistics
+			return -1, rhsPseudo // right wins and has statistics (rhsPseudo==false)
 		}
 		if preferRange {
 			// keep an index without statistics if that index has more equal/IN predicates, AND:
 			// 1) there are at least 2 equal/INs
 			// 2) OR - it's a full index match for all index predicates
 			if lhsPseudo && lhs.path.EqOrInCondCount > rhs.path.EqOrInCondCount && globalResult >= 0 && sum >= 0 &&
 				(lhs.path.EqOrInCondCount > 1 || (lhs.path.EqOrInCondCount > 0 && len(lhs.indexCondsColMap) >= len(lhs.path.Index.Columns))) {
-				return 1, true // left wins and does NOT have statistics
+				return 1, lhsPseudo // left wins and does NOT have statistics (lhsPseudo==true)
 			}
 			if rhsPseudo && rhs.path.EqOrInCondCount > lhs.path.EqOrInCondCount && globalResult <= 0 && sum <= 0 &&
 				(rhs.path.EqOrInCondCount > 1 || (rhs.path.EqOrInCondCount > 0 && len(rhs.indexCondsColMap) >= len(rhs.path.Index.Columns))) {
-				return -1, true // right wins and does NOT have statistics
+				return -1, rhsPseudo // right wins and does NOT have statistics (rhsPseudo==true)
 			}
 		}
 	}
@@ -789,10 +789,10 @@ func compareCandidates(sctx base.PlanContext, statsTbl *statistics.Table, tableI
 		threshold := float64(fixcontrol.GetIntWithDefault(sctx.GetSessionVars().OptimizerFixControl, fixcontrol.Fix45132, 1000))
 		if threshold > 0 { // set it to 0 to disable this rule
 			if lhs.path.CountAfterAccess/rhs.path.CountAfterAccess > threshold {
-				return -1, false
+				return -1, rhsPseudo // right wins - also return whether it has statistics (pseudo) or not
 			}
 			if rhs.path.CountAfterAccess/lhs.path.CountAfterAccess > threshold {
-				return 1, false
+				return 1, lhsPseudo // left wins - also return whether it has statistics (pseudo) or not
 			}
 		}
 	}
@@ -805,18 +805,18 @@ func compareCandidates(sctx base.PlanContext, statsTbl *statistics.Table, tableI
 	// If `x` is not worse than `y` at all factors,
 	// and there exists one factor that `x` is better than `y`, then `x` is better than `y`.
 	if !comparable1 {
-		return 0, false
+		return 0, false // No winner (0). Do not return the pseudo result
 	}
 	if !comparable2 {
-		return 0, false
+		return 0, false // No winner (0). Do not return the pseudo result
 	}
 	if accessResult >= 0 && scanResult >= 0 && matchResult >= 0 && globalResult >= 0 && sum > 0 {
-		return 1, false
+		return 1, lhsPseudo // left wins - also return whether it has statistics (pseudo) or not
 	}
 	if accessResult <= 0 && scanResult <= 0 && matchResult <= 0 && globalResult <= 0 && sum < 0 {
-		return -1, false
+		return -1, rhsPseudo // right wins - also return whether it has statistics (pseudo) or not
 	}
-	return 0, false
+	return 0, false // No winner (0). Do not return the pseudo result
 }
 
 func isMatchProp(ds *logicalop.DataSource, path *util.AccessPath, prop *property.PhysicalProperty) bool {