github.com/dolthub/go-mysql-server@v0.18.0/sql/expression/function/version.go (about)

     1  // Copyright 2020-2021 Dolthub, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package function
    16  
    17  import (
    18  	"fmt"
    19  
    20  	"github.com/dolthub/go-mysql-server/sql"
    21  	"github.com/dolthub/go-mysql-server/sql/types"
    22  )
    23  
    24  const mysqlVersion = "8.0.11"
    25  
    26  // Version is a function that returns server version.
    27  type Version string
    28  
    29  func (f Version) IsNonDeterministic() bool {
    30  	// Just means that the value can change over time, i.e. on an upgrade
    31  	return true
    32  }
    33  
    34  var _ sql.FunctionExpression = (Version)("")
    35  var _ sql.CollationCoercible = (Version)("")
    36  
    37  // NewVersion creates a new Version UDF.
    38  func NewVersion(versionPostfix string) func(...sql.Expression) (sql.Expression, error) {
    39  	return func(...sql.Expression) (sql.Expression, error) {
    40  		return Version(versionPostfix), nil
    41  	}
    42  }
    43  
    44  // FunctionName implements sql.FunctionExpression
    45  func (f Version) FunctionName() string {
    46  	return "version"
    47  }
    48  
    49  // Description implements sql.FunctionExpression
    50  func (f Version) Description() string {
    51  	return "returns a string that indicates the SQL server version."
    52  }
    53  
    54  // Type implements the Expression interface.
    55  func (f Version) Type() sql.Type { return types.LongText }
    56  
    57  // CollationCoercibility implements the interface sql.CollationCoercible.
    58  func (Version) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    59  	return sql.Collation_utf8mb3_general_ci, 3
    60  }
    61  
    62  // IsNullable implements the Expression interface.
    63  func (f Version) IsNullable() bool {
    64  	return false
    65  }
    66  
    67  func (f Version) String() string {
    68  	return fmt.Sprintf("%s()", f.FunctionName())
    69  }
    70  
    71  // WithChildren implements the Expression interface.
    72  func (f Version) WithChildren(children ...sql.Expression) (sql.Expression, error) {
    73  	if len(children) != 0 {
    74  		return nil, sql.ErrInvalidChildrenNumber.New(f, len(children), 0)
    75  	}
    76  	return f, nil
    77  }
    78  
    79  // Resolved implements the Expression interface.
    80  func (f Version) Resolved() bool {
    81  	return true
    82  }
    83  
    84  // Children implements the Expression interface.
    85  func (f Version) Children() []sql.Expression { return nil }
    86  
    87  // Eval implements the Expression interface.
    88  func (f Version) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
    89  	if f == "" {
    90  		return mysqlVersion, nil
    91  	}
    92  
    93  	return fmt.Sprintf("%s-%s", mysqlVersion, string(f)), nil
    94  }