github.com/dolthub/go-mysql-server@v0.18.0/sql/partition.go (about)

     1  // Copyright 2022 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 sql
    16  
    17  import "io"
    18  
    19  // Partition represents a partition from a SQL table.
    20  type Partition interface {
    21  	Key() []byte
    22  }
    23  
    24  // PartitionIter is an iterator that retrieves partitions.
    25  type PartitionIter interface {
    26  	Closer
    27  	Next(*Context) (Partition, error)
    28  }
    29  
    30  // PartitionsToPartitionIter creates a PartitionIter that iterates over the given partitions.
    31  func PartitionsToPartitionIter(partitions ...Partition) PartitionIter {
    32  	return &slicePartitionIter{partitions: partitions}
    33  }
    34  
    35  type slicePartitionIter struct {
    36  	partitions []Partition
    37  	idx        int
    38  }
    39  
    40  func (i *slicePartitionIter) Next(*Context) (Partition, error) {
    41  	if i.idx >= len(i.partitions) {
    42  		return nil, io.EOF
    43  	}
    44  	i.idx++
    45  	return i.partitions[i.idx-1], nil
    46  }
    47  func (i *slicePartitionIter) Close(*Context) error {
    48  	i.partitions = nil
    49  	return nil
    50  }