Hacky extension point for aggregate function determination

sql/planbuilder/aggregates.go

@@ -95,9 +95,8 @@ func (b *Builder) buildGroupingCols(fromScope, projScope *scope, groupby ast.Gro
 	// 3) an index into selects
 	// 4) a simple non-aggregate expression
 	groupings := make([]sql.Expression, 0)
-	if fromScope.groupBy == nil {
-		fromScope.initGroupBy()
-	}
+	fromScope.initGroupBy()
+
 	g := fromScope.groupBy
 	for _, e := range groupby {
 		var col scopeColumn
@@ -194,9 +193,7 @@ func (b *Builder) buildAggregation(fromScope, projScope *scope, groupingCols []s
 	// - grouping cols projection
 	// - aggregate expressions
 	// - output projection
-	if fromScope.groupBy == nil {
-		fromScope.initGroupBy()
-	}
+	fromScope.initGroupBy()
 
 	group := fromScope.groupBy
 	outScope := group.outScope
@@ -257,7 +254,10 @@ func (b *Builder) buildAggregation(fromScope, projScope *scope, groupingCols []s
 	return outScope
 }
 
-func isAggregateFunc(name string) bool {
+// IsAggregateFunc is a hacky "extension point" to allow for other dialects to declare additional aggregate functions
+var IsAggregateFunc = IsMySQLAggregateFuncName
+
+func IsMySQLAggregateFuncName(name string) bool {
 	switch name {
 	case "avg", "bit_and", "bit_or", "bit_xor", "count",
 		"group_concat", "json_arrayagg", "json_objectagg",
@@ -278,111 +278,63 @@ func (b *Builder) buildAggregateFunc(inScope *scope, name string, e *ast.FuncExp
 		b.handleErr(err)
 	}
 
-	if inScope.groupBy == nil {
-		inScope.initGroupBy()
-	}
+	inScope.initGroupBy()
 	gb := inScope.groupBy
 
 	if strings.EqualFold(name, "count") {
 		if _, ok := e.Exprs[0].(*ast.StarExpr); ok {
-			var agg sql.Aggregation
-			if e.Distinct {
-				agg = aggregation.NewCountDistinct(expression.NewLiteral(1, types.Int64))
-			} else {
-				agg = aggregation.NewCount(expression.NewLiteral(1, types.Int64))
-			}
-			b.qFlags.Set(sql.QFlagCountStar)
-			aggName := strings.ToLower(agg.String())
-			gf := gb.getAggRef(aggName)
-			if gf != nil {
-				// if we've already computed use reference here
-				return gf
-			}
-
-			col := scopeColumn{col: strings.ToLower(agg.String()), scalar: agg, typ: agg.Type(), nullable: agg.IsNullable()}
-			id := gb.outScope.newColumn(col)
-			col.id = id
-
-			agg = agg.WithId(sql.ColumnId(id)).(sql.Aggregation)
-			gb.outScope.cols[len(gb.outScope.cols)-1].scalar = agg
-			col.scalar = agg
-
-			gb.addAggStr(col)
-			return col.scalarGf()
+			return b.buildCountStarAggregate(e, gb)
 		}
 	}
 
 	if strings.EqualFold(name, "jsonarray") {
 		// TODO we don't have any tests for this
 		if _, ok := e.Exprs[0].(*ast.StarExpr); ok {
-			var agg sql.Aggregation
-			agg = aggregation.NewJsonArray(expression.NewLiteral(expression.NewStar(), types.Int64))
-			b.qFlags.Set(sql.QFlagStar)
-
-			//if e.Distinct {
-			//	agg = plan.NewDistinct(expression.NewLiteral(1, types.Int64))
-			//}
-			aggName := strings.ToLower(agg.String())
-			gf := gb.getAggRef(aggName)
-			if gf != nil {
-				// if we've already computed use reference here
-				return gf
-			}
-
-			col := scopeColumn{col: strings.ToLower(agg.String()), scalar: agg, typ: agg.Type(), nullable: agg.IsNullable()}
-			id := gb.outScope.newColumn(col)
-
-			agg = agg.WithId(sql.ColumnId(id)).(*aggregation.JsonArray)
-			gb.outScope.cols[len(gb.outScope.cols)-1].scalar = agg
-			col.scalar = agg
-
-			col.id = id
-			gb.addAggStr(col)
-			return col.scalarGf()
+			return b.buildJsonArrayStarAggregate(gb)
 		}
 	}
 
 	if strings.EqualFold(name, "any_value") {
 		b.qFlags.Set(sql.QFlagAnyAgg)
 	}
 
-	var args []sql.Expression
-	for _, arg := range e.Exprs {
-		e := b.selectExprToExpression(inScope, arg)
-		switch e := e.(type) {
-		case *expression.GetField:
-			if e.TableId() == 0 {
-				// TODO: not sure where this came from but it's not true
-				// aliases are not valid aggregate arguments, the alias must be masking a column
-				gf := b.selectExprToExpression(inScope.parent, arg)
-				var ok bool
-				e, ok = gf.(*expression.GetField)
-				if !ok || e.TableId() == 0 {
-					b.handleErr(fmt.Errorf("failed to resolve aggregate column argument: %s", gf))
-				}
-			}
-			args = append(args, e)
-			col := scopeColumn{tableId: e.TableID(), db: e.Database(), table: e.Table(), col: e.Name(), scalar: e, typ: e.Type(), nullable: e.IsNullable()}
-			gb.addInCol(col)
-		case *expression.Star:
-			err := sql.ErrStarUnsupported.New()
-			b.handleErr(err)
-		case *plan.Subquery:
-			args = append(args, e)
-			col := scopeColumn{col: e.QueryString, scalar: e, typ: e.Type()}
-			gb.addInCol(col)
-		default:
-			args = append(args, e)
-			col := scopeColumn{col: e.String(), scalar: e, typ: e.Type()}
-			gb.addInCol(col)
-		}
+	args := b.buildAggFunctionArgs(inScope, e, gb)
+	agg := b.newAggregation(e, name, args)
+
+	if name == "count" {
+		b.qFlags.Set(sql.QFlagCount)
 	}
 
+	aggType := agg.Type()
+	if name == "avg" || name == "sum" {
+		aggType = types.Float64
+	}
+
+	aggName := strings.ToLower(plan.AliasSubqueryString(agg))
+	if id, ok := gb.outScope.getExpr(aggName, true); ok {
+		// if we've already computed use reference here
+		gf := expression.NewGetFieldWithTable(int(id), 0, aggType, "", "", aggName, agg.IsNullable())
+		return gf
+	}
+
+	col := scopeColumn{col: aggName, scalar: agg, typ: aggType, nullable: agg.IsNullable()}
+	id := gb.outScope.newColumn(col)
+
+	agg = agg.WithId(sql.ColumnId(id)).(sql.Aggregation)
+	gb.outScope.cols[len(gb.outScope.cols)-1].scalar = agg
+	col.scalar = agg
+
+	col.id = id
+	gb.addAggStr(col)
+	return col.scalarGf()
+}
+
+// newAggregation creates a new aggregation function instanc from the arguments given
+func (b *Builder) newAggregation(e *ast.FuncExpr, name string, args []sql.Expression) sql.Aggregation {
 	var agg sql.Aggregation
 	if e.Distinct && name == "count" {
 		agg = aggregation.NewCountDistinct(args...)
 	} else {
-
 		// NOTE: Not all aggregate functions support DISTINCT. Fortunately, the vitess parser will throw
 		// errors for when DISTINCT is used on aggregate functions that don't support DISTINCT.
 		if e.Distinct {
@@ -412,39 +364,104 @@ func (b *Builder) buildAggregateFunc(inScope *scope, name string, e *ast.FuncExp
 			b.handleErr(err)
 		}
 	}
+	return agg
+}
 
-	if name == "count" {
-		b.qFlags.Set(sql.QFlagCount)
+// buildAggFunctionArgs builds the arguments for an aggregate function
+func (b *Builder) buildAggFunctionArgs(inScope *scope, e *ast.FuncExpr, gb *groupBy) []sql.Expression {
+	var args []sql.Expression
+	for _, arg := range e.Exprs {
+		e := b.selectExprToExpression(inScope, arg)
+		switch e := e.(type) {
+		case *expression.GetField:
+			if e.TableId() == 0 {
+				// TODO: not sure where this came from but it's not true
+				// aliases are not valid aggregate arguments, the alias must be masking a column
+				gf := b.selectExprToExpression(inScope.parent, arg)
+				var ok bool
+				e, ok = gf.(*expression.GetField)
+				if !ok || e.TableId() == 0 {
+					b.handleErr(fmt.Errorf("failed to resolve aggregate column argument: %s", gf))
+				}
+			}
+			args = append(args, e)
+			col := scopeColumn{tableId: e.TableID(), db: e.Database(), table: e.Table(), col: e.Name(), scalar: e, typ: e.Type(), nullable: e.IsNullable()}
+			gb.addInCol(col)
+		case *expression.Star:
+			err := sql.ErrStarUnsupported.New()
+			b.handleErr(err)
+		case *plan.Subquery:
+			args = append(args, e)
+			col := scopeColumn{col: e.QueryString, scalar: e, typ: e.Type()}
+			gb.addInCol(col)
+		default:
+			args = append(args, e)
+			col := scopeColumn{col: e.String(), scalar: e, typ: e.Type()}
+			gb.addInCol(col)
+		}
 	}
+	return args
+}
 
-	aggType := agg.Type()
-	if name == "avg" || name == "sum" {
-		aggType = types.Float64
+// buildJsonArrayStarAggregate builds a JSON_ARRAY(*) aggregate function
+func (b *Builder) buildJsonArrayStarAggregate(gb *groupBy) sql.Expression {
+	var agg sql.Aggregation
+	agg = aggregation.NewJsonArray(expression.NewLiteral(expression.NewStar(), types.Int64))
+	b.qFlags.Set(sql.QFlagStar)
+
+	// if e.Distinct {
+	//	agg = plan.NewDistinct(expression.NewLiteral(1, types.Int64))
+	// }
+	aggName := strings.ToLower(agg.String())
+	gf := gb.getAggRef(aggName)
+	if gf != nil {
+		// if we've already computed use reference here
+		return gf
 	}
 
-	aggName := strings.ToLower(plan.AliasSubqueryString(agg))
-	if id, ok := gb.outScope.getExpr(aggName, true); ok {
+	col := scopeColumn{col: strings.ToLower(agg.String()), scalar: agg, typ: agg.Type(), nullable: agg.IsNullable()}
+	id := gb.outScope.newColumn(col)
+
+	agg = agg.WithId(sql.ColumnId(id)).(*aggregation.JsonArray)
+	gb.outScope.cols[len(gb.outScope.cols)-1].scalar = agg
+	col.scalar = agg
+
+	col.id = id
+	gb.addAggStr(col)
+	return col.scalarGf()
+}
+
+// buildCountStarAggregate builds a COUNT(*) aggregate function
+func (b *Builder) buildCountStarAggregate(e *ast.FuncExpr, gb *groupBy) sql.Expression {
+	var agg sql.Aggregation
+	if e.Distinct {
+		agg = aggregation.NewCountDistinct(expression.NewLiteral(1, types.Int64))
+	} else {
+		agg = aggregation.NewCount(expression.NewLiteral(1, types.Int64))
+	}
+	b.qFlags.Set(sql.QFlagCountStar)
+	aggName := strings.ToLower(agg.String())
+	gf := gb.getAggRef(aggName)
+	if gf != nil {
 		// if we've already computed use reference here
-		gf := expression.NewGetFieldWithTable(int(id), 0, aggType, "", "", aggName, agg.IsNullable())
 		return gf
 	}
 
-	col := scopeColumn{col: aggName, scalar: agg, typ: aggType, nullable: agg.IsNullable()}
+	col := scopeColumn{col: strings.ToLower(agg.String()), scalar: agg, typ: agg.Type(), nullable: agg.IsNullable()}
 	id := gb.outScope.newColumn(col)
+	col.id = id
 
 	agg = agg.WithId(sql.ColumnId(id)).(sql.Aggregation)
 	gb.outScope.cols[len(gb.outScope.cols)-1].scalar = agg
 	col.scalar = agg
 
-	col.id = id
 	gb.addAggStr(col)
 	return col.scalarGf()
 }
 
+// buildGroupConcat builds a GROUP_CONCAT aggregate function
 func (b *Builder) buildGroupConcat(inScope *scope, e *ast.GroupConcatExpr) sql.Expression {
-	if inScope.groupBy == nil {
-		inScope.initGroupBy()
-	}
+	inScope.initGroupBy()
 	gb := inScope.groupBy
 
 	args := make([]sql.Expression, len(e.Exprs))
@@ -794,7 +811,7 @@ func (b *Builder) analyzeHaving(fromScope, projScope *scope, having *ast.Where)
 			return false, nil
 		case *ast.FuncExpr:
 			name := n.Name.Lowered()
-			if isAggregateFunc(name) {
+			if IsAggregateFunc(name) {
 				// record aggregate
 				// TODO: this should get projScope as well
 				_ = b.buildAggregateFunc(fromScope, name, n)
@@ -874,9 +891,7 @@ func (b *Builder) buildHaving(fromScope, projScope, outScope *scope, having *ast
 	if having == nil {
 		return
 	}
-	if fromScope.groupBy == nil {
-		fromScope.initGroupBy()
-	}
+	fromScope.initGroupBy()
 
 	havingScope := b.newScope()
 	if fromScope.parent != nil {

sql/planbuilder/scalar.go

@@ -153,7 +153,7 @@ func (b *Builder) buildScalar(inScope *scope, e ast.Expr) (ex sql.Expression) {
 			return b.buildNameConst(inScope, v)
 		} else if name == "icu_version" {
 			return expression.NewLiteral(icuVersion, types.MustCreateString(query.Type_VARCHAR, int64(len(icuVersion)), sql.Collation_Default))
-		} else if isAggregateFunc(name) && v.Over == nil {
+		} else if IsAggregateFunc(name) && v.Over == nil {
 			// TODO this assumes aggregate is in the same scope
 			// also need to avoid nested aggregates
 			return b.buildAggregateFunc(inScope, name, v)

sql/planbuilder/scope.go

@@ -224,7 +224,9 @@ func (s *scope) initProc() {
 // initGroupBy creates a container scope for aggregation
 // functions and function inputs.
 func (s *scope) initGroupBy() {
-	s.groupBy = &groupBy{outScope: s.replace()}
+	if s.groupBy == nil {
+		s.groupBy = &groupBy{outScope: s.replace()}
+	}
 }
 
 // pushSubquery creates a new scope with the subquery already initialized.

sql/planbuilder/show.go

@@ -614,7 +614,7 @@ func (b *Builder) buildAsOfExpr(inScope *scope, time ast.Expr) sql.Expression {
 		return expression.NewLiteral(v.String(), types.LongText)
 	case *ast.FuncExpr:
 		// todo(max): more specific validation for nested ASOF functions
-		if isWindowFunc(v.Name.Lowered()) || isAggregateFunc(v.Name.Lowered()) {
+		if isWindowFunc(v.Name.Lowered()) || IsAggregateFunc(v.Name.Lowered()) {
 			err := sql.ErrInvalidAsOfExpression.New(v)
 			b.handleErr(err)
 		}