vtgate sql: consolidate common code

Some boiler-plate behaviors were accumulating in each builder.
They've now been consolidated under builderCommon.

Signed-off-by: Sugu Sougoumarane <ssougou@gmail.com>

go/vt/vtgate/planbuilder/builder.go

@@ -107,6 +107,50 @@ type builder interface {
 	Primitive() engine.Primitive
 }
 
+// builderCommon implements some common functionality of builders.
+// Make sure to override in case behavior needs to be changed.
+type builderCommon struct {
+	order int
+	input builder
+}
+
+func (bc *builderCommon) Order() int {
+	return bc.order
+}
+
+func (bc *builderCommon) Reorder(order int) {
+	bc.input.Reorder(order)
+	bc.order = bc.input.Order() + 1
+}
+
+func (bc *builderCommon) First() builder {
+	return bc.input.First()
+}
+
+func (bc *builderCommon) ResultColumns() []*resultColumn {
+	return bc.input.ResultColumns()
+}
+
+func (bc *builderCommon) SetUpperLimit(count *sqlparser.SQLVal) {
+	bc.input.SetUpperLimit(count)
+}
+
+func (bc *builderCommon) PushMisc(sel *sqlparser.Select) {
+	bc.input.PushMisc(sel)
+}
+
+func (bc *builderCommon) Wireup(bldr builder, jt *jointab) error {
+	return bc.input.Wireup(bldr, jt)
+}
+
+func (bc *builderCommon) SupplyVar(from, to int, col *sqlparser.ColName, varname string) {
+	bc.input.SupplyVar(from, to, col, varname)
+}
+
+func (bc *builderCommon) SupplyCol(col *sqlparser.ColName) (rc *resultColumn, colnum int) {
+	return bc.input.SupplyCol(col)
+}
+
 // ContextVSchema defines the interface for this package to fetch
 // info about tables.
 type ContextVSchema interface {

go/vt/vtgate/planbuilder/limit.go

@@ -32,48 +32,24 @@ var _ builder = (*limit)(nil)
 // operation. Since a limit is the final operation
 // of a SELECT, most pushes are not applicable.
 type limit struct {
-	order         int
-	resultColumns []*resultColumn
-	input         builder
+	builderCommon
 	elimit *engine.Limit
 }
 
 // newLimit builds a new limit.
 func newLimit(bldr builder) *limit {
 	return &limit{
-		resultColumns: bldr.ResultColumns(),
-		input:         bldr,
+		builderCommon: builderCommon{input: bldr},
 		elimit:        &engine.Limit{},
 	}
 }
 
-// Order satisfies the builder interface.
-func (l *limit) Order() int {
-	return l.order
-}
-
-// Reorder satisfies the builder interface.
-func (l *limit) Reorder(order int) {
-	l.input.Reorder(order)
-	l.order = l.input.Order() + 1
-}
-
 // Primitive satisfies the builder interface.
 func (l *limit) Primitive() engine.Primitive {
 	l.elimit.Input = l.input.Primitive()
 	return l.elimit
 }
 
-// First satisfies the builder interface.
-func (l *limit) First() builder {
-	return l.input.First()
-}
-
-// ResultColumns satisfies the builder interface.
-func (l *limit) ResultColumns() []*resultColumn {
-	return l.resultColumns
-}
-
 // PushFilter satisfies the builder interface.
 func (l *limit) PushFilter(_ *primitiveBuilder, _ sqlparser.Expr, whereType string, _ builder) error {
 	return errors.New("limit.PushFilter: unreachable")
@@ -136,23 +112,3 @@ func (l *limit) SetLimit(limit *sqlparser.Limit) error {
 // In the future, we may have to honor this call for subqueries.
 func (l *limit) SetUpperLimit(count *sqlparser.SQLVal) {
 }
-
-// PushMisc satisfies the builder interface.
-func (l *limit) PushMisc(sel *sqlparser.Select) {
-	l.input.PushMisc(sel)
-}
-
-// Wireup satisfies the builder interface.
-func (l *limit) Wireup(bldr builder, jt *jointab) error {
-	return l.input.Wireup(bldr, jt)
-}
-
-// SupplyVar satisfies the builder interface.
-func (l *limit) SupplyVar(from, to int, col *sqlparser.ColName, varname string) {
-	l.input.SupplyVar(from, to, col, varname)
-}
-
-// SupplyCol satisfies the builder interface.
-func (l *limit) SupplyCol(col *sqlparser.ColName) (rc *resultColumn, colnum int) {
-	panic("BUG: nothing should depend on LIMIT")
-}

go/vt/vtgate/planbuilder/memory_sort.go

@@ -32,17 +32,16 @@ var _ builder = (*memorySort)(nil)
 // operation. Since a limit is the final operation
 // of a SELECT, most pushes are not applicable.
 type memorySort struct {
-	order         int
+	builderCommon
 	resultColumns []*resultColumn
-	input         builder
 	eMemorySort   *engine.MemorySort
 }
 
 // newMemorySort builds a new memorySort.
 func newMemorySort(bldr builder, orderBy sqlparser.OrderBy) (*memorySort, error) {
 	ms := &memorySort{
+		builderCommon: builderCommon{input: bldr},
 		resultColumns: bldr.ResultColumns(),
-		input:         bldr,
 		eMemorySort:   &engine.MemorySort{},
 	}
 	for _, order := range orderBy {
@@ -78,28 +77,12 @@ func newMemorySort(bldr builder, orderBy sqlparser.OrderBy) (*memorySort, error)
 	return ms, nil
 }
 
-// Order satisfies the builder interface.
-func (ms *memorySort) Order() int {
-	return ms.order
-}
-
-// Reorder satisfies the builder interface.
-func (ms *memorySort) Reorder(order int) {
-	ms.input.Reorder(order)
-	ms.order = ms.input.Order() + 1
-}
-
 // Primitive satisfies the builder interface.
 func (ms *memorySort) Primitive() engine.Primitive {
 	ms.eMemorySort.Input = ms.input.Primitive()
 	return ms.eMemorySort
 }
 
-// First satisfies the builder interface.
-func (ms *memorySort) First() builder {
-	return ms.input.First()
-}
-
 // ResultColumns satisfies the builder interface.
 func (ms *memorySort) ResultColumns() []*resultColumn {
 	return ms.resultColumns
@@ -141,23 +124,3 @@ func (ms *memorySort) SetLimit(limit *sqlparser.Limit) error {
 func (ms *memorySort) SetUpperLimit(count *sqlparser.SQLVal) {
 	ms.eMemorySort.UpperLimit, _ = sqlparser.NewPlanValue(count)
 }
-
-// PushMisc satisfies the builder interface.
-func (ms *memorySort) PushMisc(sel *sqlparser.Select) {
-	ms.input.PushMisc(sel)
-}
-
-// Wireup satisfies the builder interface.
-func (ms *memorySort) Wireup(bldr builder, jt *jointab) error {
-	return ms.input.Wireup(bldr, jt)
-}
-
-// SupplyVar satisfies the builder interface.
-func (ms *memorySort) SupplyVar(from, to int, col *sqlparser.ColName, varname string) {
-	ms.input.SupplyVar(from, to, col, varname)
-}
-
-// SupplyCol satisfies the builder interface.
-func (ms *memorySort) SupplyCol(col *sqlparser.ColName) (rc *resultColumn, colnum int) {
-	panic("BUG: nothing should depend on ORDER BY")
-}

go/vt/vtgate/planbuilder/merge_sort.go

@@ -33,43 +33,21 @@ var _ builder = (*mergeSort)(nil)
 // Since ORDER BY happens near the end of the SQL processing,
 // most functions of this primitive are unreachable.
 type mergeSort struct {
-	order int
-	input *route
+	builderCommon
 }
 
 // newMergeSort builds a new mergeSort.
 func newMergeSort(rb *route) *mergeSort {
 	return &mergeSort{
-		input: rb,
+		builderCommon: builderCommon{input: rb},
 	}
 }
 
-// Order satisfies the builder interface.
-func (ms *mergeSort) Order() int {
-	return ms.order
-}
-
-// Reorder satisfies the builder interface.
-func (ms *mergeSort) Reorder(order int) {
-	ms.input.Reorder(order)
-	ms.order = ms.input.Order() + 1
-}
-
 // Primitive satisfies the builder interface.
 func (ms *mergeSort) Primitive() engine.Primitive {
 	return ms.input.Primitive()
 }
 
-// First satisfies the builder interface.
-func (ms *mergeSort) First() builder {
-	return ms.input.First()
-}
-
-// ResultColumns satisfies the builder interface.
-func (ms *mergeSort) ResultColumns() []*resultColumn {
-	return ms.input.ResultColumns()
-}
-
 // PushFilter satisfies the builder interface.
 func (ms *mergeSort) PushFilter(pb *primitiveBuilder, expr sqlparser.Expr, whereType string, origin builder) error {
 	return ms.input.PushFilter(pb, expr, whereType, origin)
@@ -96,28 +74,3 @@ func (ms *mergeSort) PushGroupBy(groupBy sqlparser.GroupBy) error {
 func (ms *mergeSort) PushOrderBy(orderBy sqlparser.OrderBy) (builder, error) {
 	return nil, errors.New("mergeSort.PushOrderBy: unreachable")
 }
-
-// SetUpperLimit satisfies the builder interface.
-func (ms *mergeSort) SetUpperLimit(count *sqlparser.SQLVal) {
-	ms.input.SetUpperLimit(count)
-}
-
-// PushMisc satisfies the builder interface.
-func (ms *mergeSort) PushMisc(sel *sqlparser.Select) {
-	ms.input.PushMisc(sel)
-}
-
-// Wireup satisfies the builder interface.
-func (ms *mergeSort) Wireup(bldr builder, jt *jointab) error {
-	return ms.input.Wireup(bldr, jt)
-}
-
-// SupplyVar satisfies the builder interface.
-func (ms *mergeSort) SupplyVar(from, to int, col *sqlparser.ColName, varname string) {
-	ms.input.SupplyVar(from, to, col, varname)
-}
-
-// SupplyCol satisfies the builder interface.
-func (ms *mergeSort) SupplyCol(col *sqlparser.ColName) (rc *resultColumn, colnum int) {
-	return ms.input.SupplyCol(col)
-}

go/vt/vtgate/planbuilder/subquery.go

@@ -36,16 +36,15 @@ var _ builder = (*subquery)(nil)
 // clause, because a route is more versatile than
 // a subquery.
 type subquery struct {
-	order         int
+	builderCommon
 	resultColumns []*resultColumn
-	input         builder
 	esubquery     *engine.Subquery
 }
 
 // newSubquery builds a new subquery.
 func newSubquery(alias sqlparser.TableIdent, bldr builder) (*subquery, *symtab, error) {
 	sq := &subquery{
-		input:     bldr,
+		builderCommon: builderCommon{input: bldr},
 		esubquery:     &engine.Subquery{},
 	}
 
@@ -69,17 +68,6 @@ func newSubquery(alias sqlparser.TableIdent, bldr builder) (*subquery, *symtab,
 	return sq, st, nil
 }
 
-// Order satisfies the builder interface.
-func (sq *subquery) Order() int {
-	return sq.order
-}
-
-// Reorder satisfies the builder interface.
-func (sq *subquery) Reorder(order int) {
-	sq.input.Reorder(order)
-	sq.order = sq.input.Order() + 1
-}
-
 // Primitive satisfies the builder interface.
 func (sq *subquery) Primitive() engine.Primitive {
 	sq.esubquery.Subquery = sq.input.Primitive()
@@ -140,29 +128,6 @@ func (sq *subquery) PushOrderBy(orderBy sqlparser.OrderBy) (builder, error) {
 	return nil, errors.New("unsupported: order by on cross-shard subquery")
 }
 
-// SetUpperLimit satisfies the builder interface.
-// For now, the call is ignored because the
-// repercussions of pushing this limit down
-// into a subquery have not been studied yet.
-// We can consider doing it in the future.
-// TODO(sougou): this could be improved.
-func (sq *subquery) SetUpperLimit(_ *sqlparser.SQLVal) {
-}
-
-// PushMisc satisfies the builder interface.
-func (sq *subquery) PushMisc(sel *sqlparser.Select) {
-}
-
-// Wireup satisfies the builder interface.
-func (sq *subquery) Wireup(bldr builder, jt *jointab) error {
-	return sq.input.Wireup(bldr, jt)
-}
-
-// SupplyVar satisfies the builder interface.
-func (sq *subquery) SupplyVar(from, to int, col *sqlparser.ColName, varname string) {
-	sq.input.SupplyVar(from, to, col, varname)
-}
-
 // SupplyCol satisfies the builder interface.
 func (sq *subquery) SupplyCol(col *sqlparser.ColName) (rc *resultColumn, colnum int) {
 	c := col.Metadata.(*column)