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absval.go
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absval.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 function
import (
"fmt"
"github.com/shopspring/decimal"
"github.com/Rock-liyi/p2pdb-store/sql"
"github.com/Rock-liyi/p2pdb-store/sql/expression"
)
// AbsVal is a function that takes the absolute value of a number
type AbsVal struct {
expression.UnaryExpression
}
var _ sql.FunctionExpression = (*AbsVal)(nil)
// NewAbsVal creates a new AbsVal expression.
func NewAbsVal(e sql.Expression) sql.Expression {
return &AbsVal{expression.UnaryExpression{Child: e}}
}
// FunctionName implements sql.FunctionExpression
func (t *AbsVal) FunctionName() string {
return "abs"
}
// Description implements sql.FunctionExpression
func (t *AbsVal) Description() string {
return "returns the absolute value of an expression."
}
// Eval implements the Expression interface.
func (t *AbsVal) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
val, err := t.Child.Eval(ctx, row)
if err != nil {
return nil, err
}
if val == nil {
return nil, nil
}
// Fucking Golang
switch x := val.(type) {
case uint, uint64, uint32, uint16, uint8:
return x, nil
case int:
if x < 0 {
return -x, nil
} else {
return x, nil
}
case int64:
if x < 0 {
return -x, nil
} else {
return x, nil
}
case int32:
if x < 0 {
return -x, nil
} else {
return x, nil
}
case int16:
if x < 0 {
return -x, nil
} else {
return x, nil
}
case int8:
if x < 0 {
return -x, nil
} else {
return x, nil
}
case float64:
if x < 0 {
return -x, nil
} else {
return x, nil
}
case float32:
if x < 0 {
return -x, nil
} else {
return x, nil
}
case decimal.Decimal:
return x.Abs(), nil
}
return nil, nil
}
// String implements the fmt.Stringer interface.
func (t *AbsVal) String() string {
return fmt.Sprintf("ABS(%s)", t.Child.String())
}
// IsNullable implements the Expression interface.
func (t *AbsVal) IsNullable() bool {
return t.Child.IsNullable()
}
// WithChildren implements the Expression interface.
func (t *AbsVal) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(t, len(children), 1)
}
return NewAbsVal(children[0]), nil
}
// Type implements the Expression interface.
func (t *AbsVal) Type() sql.Type {
return t.Child.Type()
}