vitess.io/vitess@v0.16.2/go/vt/vtgate/planbuilder/limit.go (about)

     1  /*
     2  Copyright 2019 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 planbuilder
    18  
    19  import (
    20  	"vitess.io/vitess/go/vt/vtgate/engine"
    21  )
    22  
    23  var _ logicalPlan = (*limit)(nil)
    24  
    25  // limit is the logicalPlan for engine.Limit.
    26  // This gets built if a limit needs to be applied
    27  // after rows are returned from an underlying
    28  // operation. Since a limit is the final operation
    29  // of a SELECT, most pushes are not applicable.
    30  type limit struct {
    31  	logicalPlanCommon
    32  	elimit *engine.Limit
    33  }
    34  
    35  // newLimit builds a new limit.
    36  func newLimit(plan logicalPlan) *limit {
    37  	return &limit{
    38  		logicalPlanCommon: newBuilderCommon(plan),
    39  		elimit:            &engine.Limit{},
    40  	}
    41  }
    42  
    43  // Primitive implements the logicalPlan interface
    44  func (l *limit) Primitive() engine.Primitive {
    45  	l.elimit.Input = l.input.Primitive()
    46  	return l.elimit
    47  }