misc code clean up

Author: angelamayxie

sql/analyzer/costed_index_scan.go

@@ -617,7 +617,7 @@ func (c *indexCoster) updateBest(s sql.Statistic, hist []sql.HistogramBucket, fd
 		{
 			// if no unique keys, prefer equality over ranges
 			bestConst, bestIsNull := c.getConstAndNullFilters(c.bestFilters)
-			cmpConst, cmpIsNull := c.getConstAndNullFilters(c.bestFilters)
+			cmpConst, cmpIsNull := c.getConstAndNullFilters(filters)
 			if cmpConst.Len() > bestConst.Len() {
 				update = true
 				return

sql/memo/memo.go

@@ -400,14 +400,13 @@ func (m *Memo) OptimizeRoot() error {
 // the same subgroup dependencies. After finding the best implementation
 // for a particular group, we fix the best plan for that group and recurse
 // into its parents.
-// TODO: we should not have to cost every plan, sometimes there is a provably
+// TODO: we should not have to cost every plan, sometimes there is a probably
 // best case implementation
 func (m *Memo) optimizeMemoGroup(grp *ExprGroup) error {
 	if grp.Done {
 		return nil
 	}
 
-	var err error
 	n := grp.First
 	if _, ok := n.(SourceRel); ok {
 		// We should order the search bottom-up so that physical operators
@@ -425,7 +424,7 @@ func (m *Memo) optimizeMemoGroup(grp *ExprGroup) error {
 	for n != nil {
 		var cost float64
 		for _, g := range n.Children() {
-			err = m.optimizeMemoGroup(g)
+			err := m.optimizeMemoGroup(g)
 			if err != nil {
 				return err
 			}
@@ -437,15 +436,13 @@ func (m *Memo) optimizeMemoGroup(grp *ExprGroup) error {
 		}
 
 		if grp.RelProps.Distinct.IsHash() {
-			var dCost float64
 			if sortedInputs(n) {
 				n.SetDistinct(SortedDistinctOp)
 			} else {
 				n.SetDistinct(HashDistinctOp)
 				d := &Distinct{Child: grp}
-				dCost = float64(statsForRel(m.Ctx, d).RowCount())
+				relCost += float64(statsForRel(m.Ctx, d).RowCount())
 			}
-			relCost += dCost
 		} else {
 			n.SetDistinct(NoDistinctOp)
 		}
@@ -457,9 +454,6 @@ func (m *Memo) optimizeMemoGroup(grp *ExprGroup) error {
 	}
 
 	grp.Done = true
-	if err != nil {
-		return err
-	}
 	return nil
 }
 

sql/rowexec/ddl_iters.go

@@ -2366,9 +2366,6 @@ func (b *BaseBuilder) executeAlterAutoInc(ctx *sql.Context, n *plan.AlterAutoInc
 	if !ok {
 		return plan.ErrInsertIntoNotSupported.New()
 	}
-	if err != nil {
-		return err
-	}
 
 	autoTbl, ok := insertable.(sql.AutoIncrementTable)
 	if !ok {