github.com/dolthub/go-mysql-server@v0.18.0/sql/expression/function/noarg_funcs.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  	"strings"
    19  
    20  	"github.com/dolthub/go-mysql-server/sql"
    21  )
    22  
    23  // NoArgFunc is a helper type to reduce boilerplate in functions that take no arguments. Implements most of
    24  // sql.FunctionExpression.
    25  type NoArgFunc struct {
    26  	Name    string
    27  	SQLType sql.Type
    28  }
    29  
    30  // FunctionName implements sql.FunctionExpression
    31  func (fn NoArgFunc) FunctionName() string {
    32  	return strings.ToLower(fn.Name)
    33  }
    34  
    35  // Type implements the Expression interface.
    36  func (fn NoArgFunc) Type() sql.Type { return fn.SQLType }
    37  
    38  func (fn NoArgFunc) String() string { return fn.FunctionName() + "()" }
    39  
    40  // IsNullable implements the Expression interface.
    41  func (fn NoArgFunc) IsNullable() bool { return false }
    42  
    43  // Resolved implements the Expression interface.
    44  func (fn NoArgFunc) Resolved() bool { return true }
    45  
    46  // Children implements the Expression interface.
    47  func (fn NoArgFunc) Children() []sql.Expression { return nil }
    48  
    49  // WithChildren implements the Expression interface.
    50  func NoArgFuncWithChildren(fn sql.Expression, children []sql.Expression) (sql.Expression, error) {
    51  	if len(children) != 0 {
    52  		return nil, sql.ErrInvalidChildrenNumber.New(fn, len(children), 0)
    53  	}
    54  	return fn, nil
    55  }