use interface

Author: James Cor

sql/aggregates.go

@@ -115,7 +115,7 @@ type WindowFrame interface {
 	StartNFollowing() Expression
 	// EndNPreceding returns whether a frame end preceding Expression or nil
 	EndNPreceding() Expression
-	// EndNPreceding returns whether a frame end following Expression or nil
+	// EndNFollowing returns whether a frame end following Expression or nil
 	EndNFollowing() Expression
 }
 
@@ -135,3 +135,9 @@ type AggregationBuffer interface {
 type WindowAggregation interface {
 	WindowAdaptableExpression
 }
+
+// OrderedAggregation are aggregate functions that modify the current working row with additional result columns.
+type OrderedAggregation interface {
+	// OutputExpressions gets a list of return expressions.
+	OutputExpressions() []Expression
+}

sql/analyzer/fix_exec_indexes.go

@@ -18,8 +18,6 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/dolthub/go-mysql-server/sql/expression/function/aggregation"
-
 	"github.com/dolthub/go-mysql-server/sql"
 	"github.com/dolthub/go-mysql-server/sql/expression"
 	"github.com/dolthub/go-mysql-server/sql/plan"
@@ -583,19 +581,18 @@ func (s *idxScope) visitSelf(n sql.Node) error {
 			// default nodes can't see lateral join nodes, unless we're in lateral
 			// join and lateral scopes are promoted to parent status
 			for _, e := range ne.Expressions() {
-				// groupConcat is special as it appends results to outer scope row
-				// we need to account for this extra column in the rows when assigning indexes
-				// see gms/expression/function/aggregation/group_concat.go:groupConcatBuffer.Update()
-				if gc, isGc := e.(*aggregation.GroupConcat); isGc {
-					selExprs := gc.GetSelectExprs()
+				// OrderedAggregations are special as they append results to the outer scope row
+				// We need to account for this extra column in the rows when assigning indexes
+				// Example: gms/expression/function/aggregation/group_concat.go:groupConcatBuffer.Update()
+				if ordAgg, isOrdAgg := e.(sql.OrderedAggregation); isOrdAgg {
+					selExprs := ordAgg.OutputExpressions()
 					selScope := &idxScope{}
 					for _, expr := range selExprs {
 						selScope.columns = append(selScope.columns, expr.String())
 						if gf, isGf := expr.(*expression.GetField); isGf {
 							selScope.ids = append(selScope.ids, gf.Id())
 						}
 					}
-					scope = append(scope, selScope)
 				}
 				s.expressions = append(s.expressions, fixExprToScope(e, scope...))
 			}

sql/expression/function/aggregation/group_concat.go

@@ -40,6 +40,7 @@ type GroupConcat struct {
 var _ sql.FunctionExpression = &GroupConcat{}
 var _ sql.Aggregation = &GroupConcat{}
 var _ sql.WindowAdaptableExpression = (*GroupConcat)(nil)
+var _ sql.OrderedAggregation = (*GroupConcat)(nil)
 
 func NewEmptyGroupConcat() sql.Expression {
 	return &GroupConcat{}
@@ -229,9 +230,8 @@ func (g *GroupConcat) WithChildren(children ...sql.Expression) (sql.Expression,
 	return NewGroupConcat(g.distinct, g.sf.FromExpressions(orderByExpr...), g.separator, children[sortFieldMarker:], g.maxLen), nil
 }
 
-// GetSelectExprs returns the select expressions
-// TODO: just expose the member variable
-func (g *GroupConcat) GetSelectExprs() []sql.Expression {
+// OutputExpressions implements the OrderedAggregation interface.
+func (g *GroupConcat) OutputExpressions() []sql.Expression {
 	return g.selectExprs
 }