forked from dolthub/go-mysql-server
/
sum.go
99 lines (79 loc) · 2.45 KB
/
sum.go
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// Copyright 2020-2021 Dolthub, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package aggregation
import (
"fmt"
"github.com/Sndav/go-mysql-server/sql"
"github.com/Sndav/go-mysql-server/sql/expression"
)
// Sum aggregation returns the sum of all values in the selected column.
// It implements the Aggregation interface.
type Sum struct {
expression.UnaryExpression
}
var _ sql.FunctionExpression = (*Sum)(nil)
// NewSum returns a new Sum node.
func NewSum(ctx *sql.Context, e sql.Expression) *Sum {
return &Sum{expression.UnaryExpression{Child: e}}
}
// FunctionName implements sql.FunctionExpression
func (m *Sum) FunctionName() string {
return "sum"
}
// Type returns the resultant type of the aggregation.
func (m *Sum) Type() sql.Type {
return sql.Float64
}
func (m *Sum) String() string {
return fmt.Sprintf("SUM(%s)", m.Child)
}
// WithChildren implements the Expression interface.
func (m *Sum) WithChildren(ctx *sql.Context, children ...sql.Expression) (sql.Expression, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(m, len(children), 1)
}
return NewSum(ctx, children[0]), nil
}
// NewBuffer creates a new buffer to compute the result.
func (m *Sum) NewBuffer() sql.Row {
return sql.NewRow(nil)
}
// Update implements the Aggregation interface.
func (m *Sum) Update(ctx *sql.Context, buffer, row sql.Row) error {
v, err := m.Child.Eval(ctx, row)
if err != nil {
return err
}
if v == nil {
return nil
}
val, err := sql.Float64.Convert(v)
if err != nil {
val = float64(0)
}
if buffer[0] == nil {
buffer[0] = float64(0)
}
buffer[0] = buffer[0].(float64) + val.(float64)
return nil
}
// Merge implements the Aggregation interface.
func (m *Sum) Merge(ctx *sql.Context, buffer, partial sql.Row) error {
return m.Update(ctx, buffer, partial)
}
// Eval implements the Aggregation interface.
func (m *Sum) Eval(ctx *sql.Context, buffer sql.Row) (interface{}, error) {
sum := buffer[0]
return sum, nil
}