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

     1  // Copyright 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 window
    16  
    17  import (
    18  	"strings"
    19  
    20  	"github.com/dolthub/go-mysql-server/sql"
    21  	"github.com/dolthub/go-mysql-server/sql/expression/function/aggregation"
    22  	"github.com/dolthub/go-mysql-server/sql/types"
    23  )
    24  
    25  type RowNumber struct {
    26  	window *sql.WindowDefinition
    27  	pos    int
    28  	id     sql.ColumnId
    29  }
    30  
    31  var _ sql.FunctionExpression = (*RowNumber)(nil)
    32  var _ sql.WindowAggregation = (*RowNumber)(nil)
    33  var _ sql.WindowAdaptableExpression = (*RowNumber)(nil)
    34  var _ sql.CollationCoercible = (*RowNumber)(nil)
    35  
    36  func NewRowNumber() sql.Expression {
    37  	return &RowNumber{}
    38  }
    39  
    40  // Id implements sql.IdExpression
    41  func (r *RowNumber) Id() sql.ColumnId {
    42  	return r.id
    43  }
    44  
    45  // WithId implements sql.IdExpression
    46  func (r *RowNumber) WithId(id sql.ColumnId) sql.IdExpression {
    47  	ret := *r
    48  	ret.id = id
    49  	return &ret
    50  }
    51  
    52  // Description implements sql.FunctionExpression
    53  func (r *RowNumber) Description() string {
    54  	return "returns the number of rows updated."
    55  }
    56  
    57  // Window implements sql.WindowExpression
    58  func (r *RowNumber) Window() *sql.WindowDefinition {
    59  	return r.window
    60  }
    61  
    62  // IsNullable implements sql.Expression
    63  func (r *RowNumber) Resolved() bool {
    64  	return windowResolved(r.window)
    65  }
    66  
    67  func (r *RowNumber) String() string {
    68  	sb := strings.Builder{}
    69  	sb.WriteString("row_number()")
    70  	if r.window != nil {
    71  		sb.WriteString(" ")
    72  		sb.WriteString(r.window.String())
    73  	}
    74  	return sb.String()
    75  }
    76  
    77  func (r *RowNumber) DebugString() string {
    78  	sb := strings.Builder{}
    79  	sb.WriteString("row_number()")
    80  	if r.window != nil {
    81  		sb.WriteString(" ")
    82  		sb.WriteString(sql.DebugString(r.window))
    83  	}
    84  	return sb.String()
    85  }
    86  
    87  // FunctionName implements sql.FunctionExpression
    88  func (r *RowNumber) FunctionName() string {
    89  	return "ROW_NUMBER"
    90  }
    91  
    92  // Type implements sql.Expression
    93  func (r *RowNumber) Type() sql.Type {
    94  	return types.Int64
    95  }
    96  
    97  // CollationCoercibility implements the interface sql.CollationCoercible.
    98  func (*RowNumber) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    99  	return sql.Collation_binary, 5
   100  }
   101  
   102  // IsNullable implements sql.Expression
   103  func (r *RowNumber) IsNullable() bool {
   104  	return false
   105  }
   106  
   107  // Eval implements sql.Expression
   108  func (r *RowNumber) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
   109  	return nil, sql.ErrWindowUnsupported.New(r.FunctionName())
   110  }
   111  
   112  // Children implements sql.Expression
   113  func (r *RowNumber) Children() []sql.Expression {
   114  	return r.window.ToExpressions()
   115  }
   116  
   117  // WithChildren implements sql.Expression
   118  func (r *RowNumber) WithChildren(children ...sql.Expression) (sql.Expression, error) {
   119  	window, err := r.window.FromExpressions(children)
   120  	if err != nil {
   121  		return nil, err
   122  	}
   123  
   124  	return r.WithWindow(window), nil
   125  }
   126  
   127  // WithWindow implements sql.WindowAggregation
   128  func (r *RowNumber) WithWindow(window *sql.WindowDefinition) sql.WindowAdaptableExpression {
   129  	nr := *r
   130  	nr.window = window
   131  	return &nr
   132  }
   133  
   134  func (r *RowNumber) NewWindowFunction() (sql.WindowFunction, error) {
   135  	return aggregation.NewRowNumber(), nil
   136  }