github.com/dolthub/go-mysql-server@v0.18.0/sql/plan/distinct.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 plan
    16  
    17  import (
    18  	"github.com/dolthub/go-mysql-server/sql"
    19  )
    20  
    21  // Distinct is a node that ensures all rows that come from it are unique.
    22  type Distinct struct {
    23  	UnaryNode
    24  }
    25  
    26  var _ sql.Node = (*Distinct)(nil)
    27  var _ sql.CollationCoercible = (*Distinct)(nil)
    28  
    29  // NewDistinct creates a new Distinct node.
    30  func NewDistinct(child sql.Node) *Distinct {
    31  	return &Distinct{
    32  		UnaryNode: UnaryNode{Child: child},
    33  	}
    34  }
    35  
    36  // Resolved implements the Resolvable interface.
    37  func (d *Distinct) Resolved() bool {
    38  	return d.UnaryNode.Child.Resolved()
    39  }
    40  
    41  // WithChildren implements the Node interface.
    42  func (d *Distinct) WithChildren(children ...sql.Node) (sql.Node, error) {
    43  	if len(children) != 1 {
    44  		return nil, sql.ErrInvalidChildrenNumber.New(d, len(children), 1)
    45  	}
    46  
    47  	return NewDistinct(children[0]), nil
    48  }
    49  
    50  // CheckPrivileges implements the interface sql.Node.
    51  func (d *Distinct) CheckPrivileges(ctx *sql.Context, opChecker sql.PrivilegedOperationChecker) bool {
    52  	return d.Child.CheckPrivileges(ctx, opChecker)
    53  }
    54  
    55  func (d *Distinct) IsReadOnly() bool {
    56  	return d.Child.IsReadOnly()
    57  }
    58  
    59  // CollationCoercibility implements the interface sql.CollationCoercible.
    60  func (d *Distinct) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    61  	return sql.GetCoercibility(ctx, d.Child)
    62  }
    63  
    64  // Describe implements sql.Describable
    65  func (d Distinct) Describe(options sql.DescribeOptions) string {
    66  	p := sql.NewTreePrinter()
    67  	_ = p.WriteNode("Distinct")
    68  	_ = p.WriteChildren(sql.Describe(d.Child, options))
    69  	return p.String()
    70  }
    71  
    72  // String implements fmt.Stringer
    73  func (d Distinct) String() string {
    74  	p := sql.NewTreePrinter()
    75  	_ = p.WriteNode("Distinct")
    76  	_ = p.WriteChildren(d.Child.String())
    77  	return p.String()
    78  }
    79  
    80  // DebugString implements sql.DebugStringer
    81  func (d Distinct) DebugString() string {
    82  	p := sql.NewTreePrinter()
    83  	_ = p.WriteNode("Distinct")
    84  	_ = p.WriteChildren(sql.DebugString(d.Child))
    85  	return p.String()
    86  }
    87  
    88  // OrderedDistinct is a Distinct node optimized for sorted row sets.
    89  // It's 2 orders of magnitude faster and uses 2 orders of magnitude less memory.
    90  type OrderedDistinct struct {
    91  	UnaryNode
    92  }
    93  
    94  var _ sql.Node = (*OrderedDistinct)(nil)
    95  var _ sql.CollationCoercible = (*OrderedDistinct)(nil)
    96  
    97  // NewOrderedDistinct creates a new OrderedDistinct node.
    98  func NewOrderedDistinct(child sql.Node) *OrderedDistinct {
    99  	if d, ok := child.(*OrderedDistinct); ok {
   100  		child = d.Child
   101  	}
   102  	return &OrderedDistinct{
   103  		UnaryNode: UnaryNode{Child: child},
   104  	}
   105  }
   106  
   107  // Resolved implements the Resolvable interface.
   108  func (d *OrderedDistinct) Resolved() bool {
   109  	return d.UnaryNode.Child.Resolved()
   110  }
   111  
   112  // WithChildren implements the Node interface.
   113  func (d *OrderedDistinct) WithChildren(children ...sql.Node) (sql.Node, error) {
   114  	if len(children) != 1 {
   115  		return nil, sql.ErrInvalidChildrenNumber.New(d, len(children), 1)
   116  	}
   117  
   118  	return NewOrderedDistinct(children[0]), nil
   119  }
   120  
   121  // CheckPrivileges implements the interface sql.Node.
   122  func (d *OrderedDistinct) CheckPrivileges(ctx *sql.Context, opChecker sql.PrivilegedOperationChecker) bool {
   123  	return d.Child.CheckPrivileges(ctx, opChecker)
   124  }
   125  
   126  func (d *OrderedDistinct) IsReadOnly() bool {
   127  	return d.Child.IsReadOnly()
   128  }
   129  
   130  // CollationCoercibility implements the interface sql.CollationCoercible.
   131  func (d *OrderedDistinct) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
   132  	return sql.GetCoercibility(ctx, d.Child)
   133  }
   134  
   135  func (d OrderedDistinct) String() string {
   136  	p := sql.NewTreePrinter()
   137  	_ = p.WriteNode("OrderedDistinct")
   138  	_ = p.WriteChildren(d.Child.String())
   139  	return p.String()
   140  }
   141  
   142  func (d OrderedDistinct) DebugString() string {
   143  	p := sql.NewTreePrinter()
   144  	_ = p.WriteNode("OrderedDistinct")
   145  	_ = p.WriteChildren(sql.DebugString(d.Child))
   146  	return p.String()
   147  }