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

     1  // Copyright 2024 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  	"github.com/dolthub/go-mysql-server/sql"
    19  	"github.com/dolthub/go-mysql-server/sql/types"
    20  )
    21  
    22  // Space implements the sql function "space" which returns a string with the number of spaces specified by the argument
    23  type Space struct {
    24  	*UnaryFunc
    25  }
    26  
    27  var _ sql.FunctionExpression = (*Space)(nil)
    28  var _ sql.CollationCoercible = (*Space)(nil)
    29  
    30  func NewSpace(arg sql.Expression) sql.Expression {
    31  	return &Space{NewUnaryFunc(arg, "SPACE", types.LongText)}
    32  }
    33  
    34  // Description implements sql.FunctionExpression
    35  func (s *Space) Description() string {
    36  	return "return a string of the specified number of spaces."
    37  }
    38  
    39  // CollationCoercibility implements the interface sql.CollationCoercible.
    40  func (s *Space) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    41  	return sql.Collation_binary, 5
    42  }
    43  
    44  // Eval implements the sql.Expression interface
    45  func (s *Space) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
    46  	val, err := s.EvalChild(ctx, row)
    47  	if err != nil {
    48  		return nil, err
    49  	}
    50  
    51  	if val == nil {
    52  		return nil, nil
    53  	}
    54  
    55  	// TODO: better truncate integer handling
    56  	v, _, err := types.Int64.Convert(val)
    57  	if err != nil {
    58  		ctx.Warn(1292, "Truncated incorrect INTEGER value: '%v'", val)
    59  		v = int64(0)
    60  	}
    61  
    62  	num := int(v.(int64))
    63  	if num < 0 {
    64  		num = 0
    65  	}
    66  
    67  	res := ""
    68  	for i := 0; i < num; i++ {
    69  		res += " "
    70  	}
    71  	return res, nil
    72  }
    73  
    74  // WithChildren implements the sql.Expression interface
    75  func (s *Space) WithChildren(children ...sql.Expression) (sql.Expression, error) {
    76  	if len(children) != 1 {
    77  		return nil, sql.ErrInvalidChildrenNumber.New(s, len(children), 1)
    78  	}
    79  	return NewSpace(children[0]), nil
    80  }