github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/pkg/sql/zero.go (about)

     1  // Copyright 2016 The Cockroach Authors.
     2  //
     3  // Use of this software is governed by the Business Source License
     4  // included in the file licenses/BSL.txt.
     5  //
     6  // As of the Change Date specified in that file, in accordance with
     7  // the Business Source License, use of this software will be governed
     8  // by the Apache License, Version 2.0, included in the file
     9  // licenses/APL.txt.
    10  
    11  package sql
    12  
    13  import (
    14  	"context"
    15  
    16  	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
    17  	"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
    18  )
    19  
    20  // zeroNode is a planNode with no columns and no rows and is used for nodes that
    21  // have no results. (e.g. a table for which the filtering condition has a
    22  // contradiction).
    23  type zeroNode struct {
    24  	columns sqlbase.ResultColumns
    25  }
    26  
    27  func newZeroNode(columns sqlbase.ResultColumns) *zeroNode {
    28  	return &zeroNode{columns: columns}
    29  }
    30  
    31  func (*zeroNode) startExec(runParams) error    { return nil }
    32  func (*zeroNode) Next(runParams) (bool, error) { return false, nil }
    33  func (*zeroNode) Values() tree.Datums          { return nil }
    34  func (*zeroNode) Close(context.Context)        {}