vitess.io/vitess@v0.16.2/go/vt/vtgate/engine/singlerow.go (about)

     1  /*
     2  Copyright 2020 The Vitess Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package engine
    18  
    19  import (
    20  	"context"
    21  
    22  	"vitess.io/vitess/go/sqltypes"
    23  	querypb "vitess.io/vitess/go/vt/proto/query"
    24  )
    25  
    26  var _ Primitive = (*SingleRow)(nil)
    27  
    28  // SingleRow defines an empty result
    29  type SingleRow struct {
    30  	noInputs
    31  	noTxNeeded
    32  }
    33  
    34  // RouteType returns a description of the query routing type used by the primitive
    35  func (s *SingleRow) RouteType() string {
    36  	return ""
    37  }
    38  
    39  // GetKeyspaceName specifies the Keyspace that this primitive routes to.
    40  func (s *SingleRow) GetKeyspaceName() string {
    41  	return ""
    42  }
    43  
    44  // GetTableName specifies the table that this primitive routes to.
    45  func (s *SingleRow) GetTableName() string {
    46  	return ""
    47  }
    48  
    49  // TryExecute performs a non-streaming exec.
    50  func (s *SingleRow) TryExecute(context.Context, VCursor, map[string]*querypb.BindVariable, bool) (*sqltypes.Result, error) {
    51  	result := sqltypes.Result{
    52  		Rows: [][]sqltypes.Value{
    53  			{},
    54  		},
    55  	}
    56  	return &result, nil
    57  }
    58  
    59  // TryStreamExecute performs a streaming exec.
    60  func (s *SingleRow) TryStreamExecute(ctx context.Context, vcursor VCursor, bindVars map[string]*querypb.BindVariable, wantfields bool, callback func(*sqltypes.Result) error) error {
    61  	res, err := s.TryExecute(ctx, vcursor, bindVars, wantfields)
    62  	if err != nil {
    63  		return err
    64  	}
    65  	return callback(res)
    66  }
    67  
    68  // GetFields fetches the field info.
    69  func (s *SingleRow) GetFields(ctx context.Context, vcursor VCursor, bindVars map[string]*querypb.BindVariable) (*sqltypes.Result, error) {
    70  	return &sqltypes.Result{}, nil
    71  }
    72  
    73  func (s *SingleRow) description() PrimitiveDescription {
    74  	return PrimitiveDescription{
    75  		OperatorType: "SingleRow",
    76  	}
    77  }