github.com/dolthub/go-mysql-server@v0.18.0/sql/expression/function/concat_ws.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  	"strings"
    20  
    21  	"github.com/dolthub/go-mysql-server/sql"
    22  	"github.com/dolthub/go-mysql-server/sql/types"
    23  )
    24  
    25  // ConcatWithSeparator joins several strings together. The first argument is
    26  // the separator for the rest of the arguments. The separator is added between
    27  // the strings to be concatenated. The separator can be a string, as can the
    28  // rest of the arguments. If the separator is NULL, the result is NULL.
    29  type ConcatWithSeparator struct {
    30  	args []sql.Expression
    31  }
    32  
    33  var _ sql.FunctionExpression = (*ConcatWithSeparator)(nil)
    34  var _ sql.CollationCoercible = (*ConcatWithSeparator)(nil)
    35  
    36  // NewConcatWithSeparator creates a new NewConcatWithSeparator UDF.
    37  func NewConcatWithSeparator(args ...sql.Expression) (sql.Expression, error) {
    38  	if len(args) == 0 {
    39  		return nil, sql.ErrInvalidArgumentNumber.New("CONCAT_WS", "1 or more", 0)
    40  	}
    41  
    42  	return &ConcatWithSeparator{args}, nil
    43  }
    44  
    45  // FunctionName implements sql.FunctionExpression
    46  func (f *ConcatWithSeparator) FunctionName() string {
    47  	return "concat_ws"
    48  }
    49  
    50  // Description implements sql.FunctionExpression
    51  func (f *ConcatWithSeparator) Description() string {
    52  	return "concatenates any group of fields into a single string. The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments. If the separator is NULL, the result is NULL."
    53  }
    54  
    55  // Type implements the Expression interface.
    56  func (f *ConcatWithSeparator) Type() sql.Type { return types.LongText }
    57  
    58  // CollationCoercibility implements the interface sql.CollationCoercible.
    59  func (c *ConcatWithSeparator) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    60  	if len(c.args) == 0 {
    61  		return sql.Collation_binary, 6
    62  	}
    63  	collation, coercibility = sql.GetCoercibility(ctx, c.args[0])
    64  	for i := 1; i < len(c.args); i++ {
    65  		nextCollation, nextCoercibility := sql.GetCoercibility(ctx, c.args[i])
    66  		collation, coercibility = sql.ResolveCoercibility(collation, coercibility, nextCollation, nextCoercibility)
    67  	}
    68  	return collation, coercibility
    69  }
    70  
    71  // IsNullable implements the Expression interface.
    72  func (f *ConcatWithSeparator) IsNullable() bool {
    73  	for _, arg := range f.args {
    74  		if arg.IsNullable() {
    75  			return true
    76  		}
    77  	}
    78  	return false
    79  }
    80  
    81  func (f *ConcatWithSeparator) String() string {
    82  	var args = make([]string, len(f.args))
    83  	for i, arg := range f.args {
    84  		args[i] = arg.String()
    85  	}
    86  	return fmt.Sprintf("%s(%s)", f.FunctionName(), strings.Join(args, ","))
    87  }
    88  
    89  // WithChildren implements the Expression interface.
    90  func (*ConcatWithSeparator) WithChildren(children ...sql.Expression) (sql.Expression, error) {
    91  	return NewConcatWithSeparator(children...)
    92  }
    93  
    94  // Resolved implements the Expression interface.
    95  func (f *ConcatWithSeparator) Resolved() bool {
    96  	for _, arg := range f.args {
    97  		if !arg.Resolved() {
    98  			return false
    99  		}
   100  	}
   101  	return true
   102  }
   103  
   104  // Children implements the Expression interface.
   105  func (f *ConcatWithSeparator) Children() []sql.Expression { return f.args }
   106  
   107  // Eval implements the Expression interface.
   108  func (f *ConcatWithSeparator) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
   109  	var parts []string
   110  
   111  	for i, arg := range f.args {
   112  		val, err := arg.Eval(ctx, row)
   113  		if err != nil {
   114  			return nil, err
   115  		}
   116  
   117  		if val == nil && i == 0 {
   118  			return nil, nil
   119  		}
   120  
   121  		if val == nil {
   122  			continue
   123  		}
   124  
   125  		val, _, err = types.LongText.Convert(val)
   126  		if err != nil {
   127  			return nil, err
   128  		}
   129  
   130  		parts = append(parts, val.(string))
   131  	}
   132  
   133  	return strings.Join(parts[1:], parts[0]), nil
   134  }