github.com/hasnat/dolt/go@v0.0.0-20210628190320-9eb5d843fbb7/libraries/doltcore/sqle/sqlutil/single_partition.go (about) 1 // Copyright 2020 Dolthub, Inc. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package sqlutil 16 17 import ( 18 "io" 19 "sync" 20 21 "github.com/dolthub/dolt/go/store/types" 22 23 "github.com/dolthub/go-mysql-server/sql" 24 ) 25 26 var _ sql.Partition = SinglePartition{} 27 28 type SinglePartition struct { 29 RowData types.Map 30 } 31 32 // Key returns the key for this partition, which must uniquely identity the partition. We have only a single partition 33 // per table, so we use a constant. 34 func (sp SinglePartition) Key() []byte { 35 return []byte("single") 36 } 37 38 var _ sql.PartitionIter = SinglePartitionIter{} 39 40 type SinglePartitionIter struct { 41 once *sync.Once 42 RowData types.Map 43 } 44 45 func NewSinglePartitionIter(rowData types.Map) SinglePartitionIter { 46 return SinglePartitionIter{&sync.Once{}, rowData} 47 } 48 49 // Close is required by the sql.PartitionIter interface. Does nothing. 50 func (itr SinglePartitionIter) Close(*sql.Context) error { 51 return nil 52 } 53 54 // Next returns the next partition if there is one, or io.EOF if there isn't. 55 func (itr SinglePartitionIter) Next() (sql.Partition, error) { 56 first := false 57 itr.once.Do(func() { 58 first = true 59 }) 60 61 if !first { 62 return nil, io.EOF 63 } 64 65 return SinglePartition{itr.RowData}, nil 66 }