plan: prepare candidate index (pingcap#5809)

plan/logical_plans.go

@@ -282,12 +282,15 @@ type DataSource struct {
 	// pushedDownConds are the conditions that will be pushed down to coprocessor.
 	pushedDownConds []expression.Expression
 
+	// relevantIndices means the indices match the push down conditions
+	relevantIndices []bool
+
 	// statsAfterSelect is the statsInfo for dataSource and selection.
 	statsAfterSelect *statsInfo
 
 	statisticTable *statistics.Table
 
-	// availableIndices is used for storing result of avalableIndices function.
+	// availableIndices is used for storing result of availableIndices function.
 	availableIndices *avalableIndices
 }
 

plan/physical_plan_builder.go

@@ -201,7 +201,6 @@ func (ds *DataSource) convert2PhysicalPlan(prop *requiredProp) (task, error) {
 		return t, nil
 	}
 
-	// TODO: We have not checked if this table has a predicate. If not, we can only consider table scan.
 	indices := ds.availableIndices.indices
 	includeTableScan := ds.availableIndices.includeTableScan
 	t = invalidTask
@@ -212,7 +211,11 @@ func (ds *DataSource) convert2PhysicalPlan(prop *requiredProp) (task, error) {
 		}
 	}
 	if !includeTableScan || len(ds.pushedDownConds) > 0 || len(prop.cols) > 0 {
-		for _, idx := range indices {
+		for i, idx := range indices {
+			// TODO: We can also check if the prop matches the index columns.
+			if !ds.relevantIndices[i] && len(prop.cols) == 0 {
+				continue
+			}
 			idxTask, err := ds.convertToIndexScan(prop, idx)
 			if err != nil {
 				return nil, errors.Trace(err)

plan/property_cols_prune.go

@@ -20,11 +20,25 @@ import (
 func (ds *DataSource) preparePossibleProperties() (result [][]*expression.Column) {
 	indices := ds.availableIndices.indices
 	includeTS := ds.availableIndices.includeTableScan
+	ds.relevantIndices = make([]bool, len(indices))
 	if includeTS {
 		col := ds.getPKIsHandleCol()
 		if col != nil {
 			result = append(result, []*expression.Column{col})
 		}
+		cols := expression.ExtractColumnsFromExpressions(make([]*expression.Column, 0, 10), ds.pushedDownConds, nil)
+		for i, idx := range indices {
+			for _, col := range cols {
+				if col.ColName.L == idx.Columns[0].Name.L {
+					ds.relevantIndices[i] = true
+					break
+				}
+			}
+		}
+	} else {
+		for i := range ds.relevantIndices {
+			ds.relevantIndices[i] = true
+		}
 	}
 	for _, idx := range indices {
 		cols, _ := expression.IndexInfo2Cols(ds.schema.Columns, idx)
@@ -40,8 +54,8 @@ func (p *LogicalSelection) preparePossibleProperties() (result [][]*expression.C
 }
 
 func (p *baseLogicalPlan) preparePossibleProperties() [][]*expression.Column {
-	if len(p.children) > 0 {
-		p.children[0].preparePossibleProperties()
+	for _, ch := range p.children {
+		ch.preparePossibleProperties()
 	}
 	return nil
 }