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version.go
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version.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/dolthub/go-mysql-server/sql"
"github.com/dolthub/go-mysql-server/sql/types"
)
const mysqlVersion = "8.0.11"
// Version is a function that returns server version.
type Version string
func (f Version) IsNonDeterministic() bool {
// Just means that the value can change over time, i.e. on an upgrade
return true
}
var _ sql.FunctionExpression = (Version)("")
var _ sql.CollationCoercible = (Version)("")
// NewVersion creates a new Version UDF.
func NewVersion(versionPostfix string) func(...sql.Expression) (sql.Expression, error) {
return func(...sql.Expression) (sql.Expression, error) {
return Version(versionPostfix), nil
}
}
// FunctionName implements sql.FunctionExpression
func (f Version) FunctionName() string {
return "version"
}
// Description implements sql.FunctionExpression
func (f Version) Description() string {
return "returns a string that indicates the SQL server version."
}
// Type implements the Expression interface.
func (f Version) Type() sql.Type { return types.LongText }
// CollationCoercibility implements the interface sql.CollationCoercible.
func (Version) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
return sql.Collation_utf8mb3_general_ci, 3
}
// IsNullable implements the Expression interface.
func (f Version) IsNullable() bool {
return false
}
func (f Version) String() string {
return fmt.Sprintf("%s()", f.FunctionName())
}
// WithChildren implements the Expression interface.
func (f Version) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 0 {
return nil, sql.ErrInvalidChildrenNumber.New(f, len(children), 0)
}
return f, nil
}
// Resolved implements the Expression interface.
func (f Version) Resolved() bool {
return true
}
// Children implements the Expression interface.
func (f Version) Children() []sql.Expression { return nil }
// Eval implements the Expression interface.
func (f Version) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
if f == "" {
return mysqlVersion, nil
}
return fmt.Sprintf("%s-%s", mysqlVersion, string(f)), nil
}