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

     1  /*
     2  Copyright 2021 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  	"strconv"
    21  	"strings"
    22  
    23  	"vitess.io/vitess/go/vt/vtgate/planbuilder/plancontext"
    24  
    25  	"vitess.io/vitess/go/vt/key"
    26  	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
    27  	"vitess.io/vitess/go/vt/sqlparser"
    28  	"vitess.io/vitess/go/vt/vterrors"
    29  	"vitess.io/vitess/go/vt/vtgate/engine"
    30  )
    31  
    32  const defaultLimit = 100
    33  
    34  func buildVStreamPlan(stmt *sqlparser.VStream, vschema plancontext.VSchema) (*planResult, error) {
    35  	table, _, destTabletType, dest, err := vschema.FindTable(stmt.Table)
    36  	if err != nil {
    37  		return nil, err
    38  	}
    39  	// TODO: do we need this restriction?
    40  	if destTabletType != topodatapb.TabletType_PRIMARY {
    41  		return nil, vterrors.VT09009(destTabletType)
    42  	}
    43  	if dest == nil {
    44  		dest = key.DestinationAllShards{}
    45  	}
    46  	var pos string
    47  	if stmt.Where != nil {
    48  		pos, err = getVStreamStartPos(stmt)
    49  		if err != nil {
    50  			return nil, err
    51  		}
    52  	}
    53  	limit := defaultLimit
    54  	if stmt.Limit != nil {
    55  		count, ok := stmt.Limit.Rowcount.(*sqlparser.Literal)
    56  		if ok {
    57  			limit, _ = strconv.Atoi(count.Val)
    58  		}
    59  	}
    60  
    61  	return newPlanResult(&engine.VStream{
    62  		Keyspace:          table.Keyspace,
    63  		TargetDestination: dest,
    64  		TableName:         table.Name.CompliantName(),
    65  		Position:          pos,
    66  		Limit:             limit,
    67  	}), nil
    68  }
    69  
    70  func getVStreamStartPos(stmt *sqlparser.VStream) (string, error) {
    71  	var colName, pos string
    72  	if stmt.Where != nil {
    73  		switch v := stmt.Where.Expr.(type) {
    74  		case *sqlparser.ComparisonExpr:
    75  			if v.Operator == sqlparser.GreaterThanOp {
    76  				switch c := v.Left.(type) {
    77  				case *sqlparser.ColName:
    78  					switch val := v.Right.(type) {
    79  					case *sqlparser.Literal:
    80  						pos = val.Val
    81  					}
    82  					colName = strings.ToLower(c.Name.String())
    83  					if colName != "pos" {
    84  						return "", vterrors.VT03017()
    85  					}
    86  				}
    87  			} else {
    88  				return "", vterrors.VT03017()
    89  			}
    90  		default:
    91  			return "", vterrors.VT03017()
    92  		}
    93  	}
    94  	return pos, nil
    95  }