planner: support using DNF to construct IndexMerge to access MVIndex (#…

…40471)

* fixup

* fixup

* fixup

planner/core/indexmerge_path.go

@@ -491,6 +491,75 @@ func (ds *DataSource) generateAndPruneIndexMergePath(indexMergeConds []expressio
 	return nil
 }
 
+// generateIndexMergeOnDNF4MVIndex generates IndexMerge paths for MVIndex upon DNF filters.
+/*
+	select * from t where ((1 member of (a) and b=1) or (2 member of (a) and b=2)) and (c > 10)
+		IndexMerge(OR)
+			IndexRangeScan(a, b, [1 1, 1 1])
+			IndexRangeScan(a, b, [2 2, 2 2])
+			Selection(c > 10)
+				TableRowIdScan(t)
+	Two limitations now:
+	1). all filters in the DNF have to be used as access-filters: ((1 member of (a)) or (2 member of (a)) or b > 10) cannot be used to access the MVIndex.
+	2). cannot support json_contains: (json_contains(a, '[1, 2]') or json_contains(a, '[3, 4]')) is not supported since a single IndexMerge cannot represent this SQL.
+*/
+func (ds *DataSource) generateIndexMergeOnDNF4MVIndex(normalPathCnt int, filters []expression.Expression) (mvIndexPaths []*util.AccessPath, err error) {
+	for idx := 0; idx < normalPathCnt; idx++ {
+		if ds.possibleAccessPaths[idx].IsTablePath() || ds.possibleAccessPaths[idx].Index == nil || !ds.possibleAccessPaths[idx].Index.MVIndex {
+			continue // not a MVIndex path
+		}
+
+		idxCols, ok := ds.prepareCols4MVIndex(ds.possibleAccessPaths[idx].Index)
+		if !ok {
+			continue
+		}
+
+		for current, filter := range filters {
+			sf, ok := filter.(*expression.ScalarFunction)
+			if !ok || sf.FuncName.L != ast.LogicOr {
+				continue
+			}
+			dnfFilters := expression.FlattenDNFConditions(sf) // [(1 member of (a) and b=1), (2 member of (a) and b=2)]
+
+			// build partial paths for each dnf filter
+			cannotFit := false
+			var partialPaths []*util.AccessPath
+			for _, dnfFilter := range dnfFilters {
+				mvIndexFilters := []expression.Expression{dnfFilter}
+				if sf, ok := dnfFilter.(*expression.ScalarFunction); ok && sf.FuncName.L == ast.LogicAnd {
+					mvIndexFilters = expression.FlattenCNFConditions(sf) // (1 member of (a) and b=1) --> [(1 member of (a)), b=1]
+				}
+
+				accessFilters, remainingFilters := ds.collectFilters4MVIndex(mvIndexFilters, idxCols)
+				if len(accessFilters) == 0 || len(remainingFilters) > 0 { // limitation 1
+					cannotFit = true
+					break
+				}
+				paths, isIntersection, ok, err := ds.buildPartialPaths4MVIndex(accessFilters, idxCols, ds.possibleAccessPaths[idx].Index)
+				if err != nil {
+					return nil, err
+				}
+				if isIntersection || !ok { // limitation 2
+					cannotFit = true
+					break
+				}
+				partialPaths = append(partialPaths, paths...)
+			}
+			if cannotFit {
+				continue
+			}
+
+			var remainingFilters []expression.Expression
+			remainingFilters = append(remainingFilters, filters[:current]...)
+			remainingFilters = append(remainingFilters, filters[current+1:]...)
+
+			indexMergePath := ds.buildPartialPathUp4MVIndex(partialPaths, false, remainingFilters)
+			mvIndexPaths = append(mvIndexPaths, indexMergePath)
+		}
+	}
+	return
+}
+
 // generateIndexMergeJSONMVIndexPath generates paths for (json_member_of / json_overlaps / json_contains) on multi-valued index.
 /*
 	1. select * from t where 1 member of (a)
@@ -511,6 +580,12 @@ func (ds *DataSource) generateAndPruneIndexMergePath(indexMergeConds []expressio
 			TableRowIdScan(t)
 */
 func (ds *DataSource) generateIndexMerge4MVIndex(normalPathCnt int, filters []expression.Expression) (mvIndexPaths []*util.AccessPath, err error) {
+	dnfMVIndexPaths, err := ds.generateIndexMergeOnDNF4MVIndex(normalPathCnt, filters)
+	if err != nil {
+		return nil, err
+	}
+	mvIndexPaths = append(mvIndexPaths, dnfMVIndexPaths...)
+
 	for idx := 0; idx < normalPathCnt; idx++ {
 		if ds.possibleAccessPaths[idx].IsTablePath() || ds.possibleAccessPaths[idx].Index == nil || !ds.possibleAccessPaths[idx].Index.MVIndex {
 			continue // not a MVIndex path
@@ -526,34 +601,45 @@ func (ds *DataSource) generateIndexMerge4MVIndex(normalPathCnt int, filters []ex
 			continue
 		}
 
-		partialPaths, isIntersection, err := ds.buildPartialPaths4MVIndex(accessFilters, idxCols, ds.possibleAccessPaths[idx].Index)
+		partialPaths, isIntersection, ok, err := ds.buildPartialPaths4MVIndex(accessFilters, idxCols, ds.possibleAccessPaths[idx].Index)
 		if err != nil {
 			return nil, err
 		}
-
-		indexMergePath := &util.AccessPath{PartialIndexPaths: partialPaths}
-		indexMergePath.IndexMergeIsIntersection = isIntersection
-		indexMergePath.TableFilters = remainingFilters
-
-		// TODO: use a naive estimation strategy here now for simplicity, make it more accurate.
-		minEstRows, maxEstRows := math.MaxFloat64, -1.0
-		for _, p := range indexMergePath.PartialIndexPaths {
-			minEstRows = math.Min(minEstRows, p.CountAfterAccess)
-			maxEstRows = math.Max(maxEstRows, p.CountAfterAccess)
-		}
-		if indexMergePath.IndexMergeIsIntersection {
-			indexMergePath.CountAfterAccess = minEstRows
-		} else {
-			indexMergePath.CountAfterAccess = maxEstRows
+		if !ok {
+			continue
 		}
 
-		mvIndexPaths = append(mvIndexPaths, indexMergePath)
+		mvIndexPaths = append(mvIndexPaths, ds.buildPartialPathUp4MVIndex(partialPaths, isIntersection, remainingFilters))
 	}
 	return
 }
 
+// buildPartialPathUp4MVIndex builds these partial paths up to a complete index merge path.
+func (ds *DataSource) buildPartialPathUp4MVIndex(partialPaths []*util.AccessPath, isIntersection bool, remainingFilters []expression.Expression) *util.AccessPath {
+	indexMergePath := &util.AccessPath{PartialIndexPaths: partialPaths}
+	indexMergePath.IndexMergeIsIntersection = isIntersection
+	indexMergePath.TableFilters = remainingFilters
+
+	// TODO: use a naive estimation strategy here now for simplicity, make it more accurate.
+	minEstRows, maxEstRows := math.MaxFloat64, -1.0
+	for _, p := range indexMergePath.PartialIndexPaths {
+		minEstRows = math.Min(minEstRows, p.CountAfterAccess)
+		maxEstRows = math.Max(maxEstRows, p.CountAfterAccess)
+	}
+	if indexMergePath.IndexMergeIsIntersection {
+		indexMergePath.CountAfterAccess = minEstRows
+	} else {
+		indexMergePath.CountAfterAccess = maxEstRows
+	}
+	return indexMergePath
+}
+
+// buildPartialPaths4MVIndex builds partial paths by using these accessFilters upon this MVIndex.
+// The accessFilters must be corresponding to these idxCols.
+// OK indicates whether it builds successfully. These partial paths should be ignored if ok==false.
 func (ds *DataSource) buildPartialPaths4MVIndex(accessFilters []expression.Expression,
-	idxCols []*expression.Column, mvIndex *model.IndexInfo) ([]*util.AccessPath, bool, error) {
+	idxCols []*expression.Column, mvIndex *model.IndexInfo) (
+	partialPaths []*util.AccessPath, isIntersection bool, ok bool, err error) {
 	var virColID = -1
 	for i := range idxCols {
 		if idxCols[i].VirtualExpr != nil {
@@ -562,39 +648,38 @@ func (ds *DataSource) buildPartialPaths4MVIndex(accessFilters []expression.Expre
 		}
 	}
 	if virColID == -1 { // unexpected, no vir-col on this MVIndex
-		return nil, false, nil
+		return nil, false, false, nil
 	}
 	if len(accessFilters) <= virColID { // no filter related to the vir-col, build a partial path directly.
 		partialPath, ok, err := ds.buildPartialPath4MVIndex(accessFilters, idxCols, mvIndex)
-		return []*util.AccessPath{partialPath}, ok, err
+		return []*util.AccessPath{partialPath}, false, ok, err
 	}
 
 	virCol := idxCols[virColID]
 	jsonType := virCol.GetType().ArrayType()
 	targetJSONPath, ok := unwrapJSONCast(virCol.VirtualExpr)
 	if !ok {
-		return nil, false, nil
+		return nil, false, false, nil
 	}
 
 	// extract values related to this vir-col, for example, extract [1, 2] from `json_contains(j, '[1, 2]')`
 	var virColVals []expression.Expression
-	var isIntersection bool
 	sf, ok := accessFilters[virColID].(*expression.ScalarFunction)
 	if !ok {
-		return nil, false, nil
+		return nil, false, false, nil
 	}
 	switch sf.FuncName.L {
 	case ast.JSONMemberOf: // (1 member of a->'$.zip')
 		v, ok := unwrapJSONCast(sf.GetArgs()[0]) // cast(1 as json) --> 1
 		if !ok {
-			return nil, false, nil
+			return nil, false, false, nil
 		}
 		virColVals = append(virColVals, v)
 	case ast.JSONContains: // (json_contains(a->'$.zip', '[1, 2, 3]')
 		isIntersection = true
 		virColVals, ok = jsonArrayExpr2Exprs(ds.ctx, sf.GetArgs()[1], jsonType)
 		if !ok {
-			return nil, false, nil
+			return nil, false, false, nil
 		}
 	case ast.JSONOverlaps: // (json_overlaps(a->'$.zip', '[1, 2, 3]')
 		var jsonPathIdx int
@@ -603,33 +688,32 @@ func (ds *DataSource) buildPartialPaths4MVIndex(accessFilters []expression.Expre
 		} else if sf.GetArgs()[1].Equal(ds.ctx, targetJSONPath) {
 			jsonPathIdx = 1 // (json_overlaps('[1, 2, 3]', a->'$.zip')
 		} else {
-			return nil, false, nil
+			return nil, false, false, nil
 		}
 		var ok bool
 		virColVals, ok = jsonArrayExpr2Exprs(ds.ctx, sf.GetArgs()[1-jsonPathIdx], jsonType)
 		if !ok {
-			return nil, false, nil
+			return nil, false, false, nil
 		}
 	default:
-		return nil, false, nil
+		return nil, false, false, nil
 	}
 
-	partialPaths := make([]*util.AccessPath, 0, len(virColVals))
 	for _, v := range virColVals {
 		// rewrite json functions to EQ to calculate range, `(1 member of j)` -> `j=1`.
 		eq, err := expression.NewFunction(ds.ctx, ast.EQ, types.NewFieldType(mysql.TypeTiny), virCol, v)
 		if err != nil {
-			return nil, false, err
+			return nil, false, false, err
 		}
 		accessFilters[virColID] = eq
 
 		partialPath, ok, err := ds.buildPartialPath4MVIndex(accessFilters, idxCols, mvIndex)
 		if !ok || err != nil {
-			return nil, ok, err
+			return nil, false, ok, err
 		}
 		partialPaths = append(partialPaths, partialPath)
 	}
-	return partialPaths, isIntersection, nil
+	return partialPaths, isIntersection, true, nil
 }
 
 // buildPartialPath4MVIndex builds a partial path on this MVIndex with these accessFilters.

planner/core/indexmerge_path_test.go

@@ -56,6 +56,34 @@ index j1((cast(j1 as signed array))))`)
 	}
 }
 
+func TestDNFOnMVIndex(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec(`create table t(a int, b int, c int, j json,
+index idx1((cast(j as signed array))),
+index idx2(a, b, (cast(j as signed array)), c))`)
+
+	var input []string
+	var output []struct {
+		SQL  string
+		Plan []string
+	}
+	planSuiteData := core.GetIndexMergeSuiteData()
+	planSuiteData.LoadTestCases(t, &input, &output)
+
+	for i, query := range input {
+		testdata.OnRecord(func() {
+			output[i].SQL = query
+		})
+		result := tk.MustQuery("explain format = 'brief' " + query)
+		testdata.OnRecord(func() {
+			output[i].Plan = testdata.ConvertRowsToStrings(result.Rows())
+		})
+		result.Check(testkit.Rows(output[i].Plan...))
+	}
+}
+
 func TestCompositeMVIndex(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)

planner/core/testdata/index_merge_suite_in.json

@@ -58,6 +58,19 @@
       "select /*+ use_index_merge(t, idx2) */ * from t where a=1"
     ]
   },
+  {
+    "name": "TestDNFOnMVIndex",
+    "cases": [
+      "select /*+ use_index_merge(t, idx1) */ * from t where (1 member of (j)) or (2 member of (j))",
+      "select /*+ use_index_merge(t, idx1) */ * from t where ((1 member of (j)) or (2 member of (j))) and (a > 10)",
+      "select /*+ use_index_merge(t, idx1) */ * from t where (json_overlaps(j, '[1, 2]')) or (json_overlaps(j, '[3, 4]'))",
+      "select /*+ use_index_merge(t, idx1) */ * from t where ((json_overlaps(j, '[1, 2]')) or (json_overlaps(j, '[3, 4]'))) and (a > 10)",
+      "select /*+ use_index_merge(t, idx1) */ * from t where (json_contains(j, '[1, 2]')) or (json_contains(j, '[3, 4]'))",
+      "select /*+ use_index_merge(t, idx2) */ * from t where (a=1 and b=2 and (3 member of (j))) or (a=11 and b=12 and (13 member of (j)))",
+      "select /*+ use_index_merge(t, idx2) */ * from t where (a=1 and b=2 and (3 member of (j))) or (a=11 and b=12 and (13 member of (j)) and c=14)",
+      "select /*+ use_index_merge(t, idx2) */ * from t where ((a=1 and b=2 and (3 member of (j))) or (a=11 and b=12 and (13 member of (j)))) and (c > 10)"
+    ]
+  },
   {
     "name": "TestMVIndexSelection",
     "cases": [