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

     1  // Copyright 2019 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  )
    18  
    19  // errorIfRowsNode wraps another planNode and returns an error if the wrapped
    20  // node produces any rows.
    21  type errorIfRowsNode struct {
    22  	plan planNode
    23  
    24  	// mkErr creates the error message, given the values of the first row
    25  	// produced.
    26  	mkErr func(values tree.Datums) error
    27  
    28  	nexted bool
    29  }
    30  
    31  func (n *errorIfRowsNode) startExec(params runParams) error {
    32  	return nil
    33  }
    34  
    35  func (n *errorIfRowsNode) Next(params runParams) (bool, error) {
    36  	if n.nexted {
    37  		return false, nil
    38  	}
    39  	n.nexted = true
    40  
    41  	ok, err := n.plan.Next(params)
    42  	if err != nil {
    43  		return false, err
    44  	}
    45  	if ok {
    46  		return false, n.mkErr(n.plan.Values())
    47  	}
    48  	return false, nil
    49  }
    50  
    51  func (n *errorIfRowsNode) Values() tree.Datums {
    52  	return nil
    53  }
    54  
    55  func (n *errorIfRowsNode) Close(ctx context.Context) {
    56  	n.plan.Close(ctx)
    57  }