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vstream.go
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vstream.go
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/*
Copyright 2021 The Vitess Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package planbuilder
import (
"strconv"
"strings"
"vitess.io/vitess/go/vt/vtgate/planbuilder/plancontext"
"vitess.io/vitess/go/vt/key"
topodatapb "vitess.io/vitess/go/vt/proto/topodata"
vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
"vitess.io/vitess/go/vt/sqlparser"
"vitess.io/vitess/go/vt/vterrors"
"vitess.io/vitess/go/vt/vtgate/engine"
)
const defaultLimit = 100
func buildVStreamPlan(stmt *sqlparser.VStream, vschema plancontext.VSchema) (engine.Primitive, error) {
table, _, destTabletType, dest, err := vschema.FindTable(stmt.Table)
if err != nil {
return nil, err
}
// TODO: do we need this restriction?
if destTabletType != topodatapb.TabletType_PRIMARY {
return nil, vterrors.Errorf(vtrpcpb.Code_FAILED_PRECONDITION, "vstream is supported only for primary tablet type, current type: %v", destTabletType)
}
if dest == nil {
dest = key.DestinationAllShards{}
}
var pos string
if stmt.Where != nil {
pos, err = getVStreamStartPos(stmt)
if err != nil {
return nil, err
}
}
limit := defaultLimit
if stmt.Limit != nil {
count, ok := stmt.Limit.Rowcount.(*sqlparser.Literal)
if ok {
limit, _ = strconv.Atoi(count.Val)
}
}
return &engine.VStream{
Keyspace: table.Keyspace,
TargetDestination: dest,
TableName: table.Name.CompliantName(),
Position: pos,
Limit: limit,
}, nil
}
const errWhereFormat = "where clause can only be of the type 'pos > <value>'"
func getVStreamStartPos(stmt *sqlparser.VStream) (string, error) {
var colName, pos string
if stmt.Where != nil {
switch v := stmt.Where.Expr.(type) {
case *sqlparser.ComparisonExpr:
if v.Operator == sqlparser.GreaterThanOp {
switch c := v.Left.(type) {
case *sqlparser.ColName:
switch val := v.Right.(type) {
case *sqlparser.Literal:
pos = val.Val
}
colName = strings.ToLower(c.Name.String())
if colName != "pos" {
return "", vterrors.NewErrorf(vtrpcpb.Code_INVALID_ARGUMENT, vterrors.SyntaxError, errWhereFormat)
}
}
} else {
return "", vterrors.NewErrorf(vtrpcpb.Code_INVALID_ARGUMENT, vterrors.SyntaxError, errWhereFormat)
}
default:
return "", vterrors.NewErrorf(vtrpcpb.Code_INVALID_ARGUMENT, vterrors.SyntaxError, errWhereFormat)
}
}
return pos, nil
}