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convert_tz.go
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convert_tz.go
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// Copyright 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"
gmstime "github.com/dolthub/go-mysql-server/internal/time"
"github.com/dolthub/go-mysql-server/sql"
"github.com/dolthub/go-mysql-server/sql/types"
)
type ConvertTz struct {
dt sql.Expression
fromTz sql.Expression
toTz sql.Expression
}
var _ sql.FunctionExpression = (*ConvertTz)(nil)
var _ sql.CollationCoercible = (*ConvertTz)(nil)
// NewConvertTz returns an implementation of the CONVERT_TZ() function.
func NewConvertTz(dt, fromTz, toTz sql.Expression) sql.Expression {
return &ConvertTz{
dt: dt,
fromTz: fromTz,
toTz: toTz,
}
}
// FunctionName implements sql.FunctionExpression
func (c *ConvertTz) FunctionName() string {
return "convert_tz"
}
// Description implements the sql.FunctionExpression interface.
func (c *ConvertTz) Description() string {
return "converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value."
}
// Resolved implements the sql.Expression interface.
func (c *ConvertTz) Resolved() bool {
return c.dt.Resolved() && c.fromTz.Resolved() && c.toTz.Resolved()
}
// String implements the sql.Expression interface.
func (c *ConvertTz) String() string {
return fmt.Sprintf("%s(%s,%s,%s)", c.FunctionName(), c.dt, c.fromTz, c.toTz)
}
// Type implements the sql.Expression interface.
func (c *ConvertTz) Type() sql.Type {
return types.DatetimeMaxPrecision
}
// CollationCoercibility implements the interface sql.CollationCoercible.
func (*ConvertTz) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
return sql.Collation_binary, 5
}
// IsNullable implements the sql.Expression interface.
func (c *ConvertTz) IsNullable() bool {
return true
}
// Eval implements the sql.Expression interface.
func (c *ConvertTz) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
from, err := c.fromTz.Eval(ctx, row)
if err != nil {
return nil, err
}
to, err := c.toTz.Eval(ctx, row)
if err != nil {
return nil, err
}
dt, err := c.dt.Eval(ctx, row)
if err != nil {
return nil, err
}
// If either the date, or the timezones/offsets are not correct types we return NULL.
datetime, err := types.DatetimeMaxPrecision.ConvertWithoutRangeCheck(dt)
if err != nil {
return nil, nil
}
fromStr, ok := from.(string)
if !ok {
return nil, nil
}
if fromStr == "SYSTEM" {
fromStr = gmstime.SystemTimezoneOffset()
}
toStr, ok := to.(string)
if !ok {
return nil, nil
}
if toStr == "SYSTEM" {
toStr = gmstime.SystemTimezoneOffset()
}
converted, success := gmstime.ConvertTimeZone(datetime, fromStr, toStr)
if !success {
return nil, nil
}
return types.DatetimeMaxPrecision.ConvertWithoutRangeCheck(converted)
}
// Children implements the sql.Expression interface.
func (c *ConvertTz) Children() []sql.Expression {
return []sql.Expression{c.dt, c.fromTz, c.toTz}
}
// WithChildren implements the sql.Expression interface.
func (c *ConvertTz) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 3 {
return nil, sql.ErrInvalidChildrenNumber.New(c, len(children), 3)
}
return NewConvertTz(children[0], children[1], children[2]), nil
}