github.com/vescale/zgraph@v0.0.0-20230410094002-959c02d50f95/stmtctx/id_range.go (about)

     1  // Copyright 2022 zGraph Authors. All rights reserved.
     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 stmtctx
    16  
    17  import (
    18  	"sync/atomic"
    19  
    20  	"github.com/vescale/zgraph/catalog"
    21  	"github.com/vescale/zgraph/meta"
    22  	"github.com/vescale/zgraph/storage/kv"
    23  )
    24  
    25  // IDRange represents an ID range. The ID range will be (base, max]
    26  type IDRange struct {
    27  	base atomic.Int64
    28  	max  int64
    29  }
    30  
    31  // NewIDRange returns a new ID range.
    32  func NewIDRange(base, max int64) *IDRange {
    33  	idr := &IDRange{
    34  		max: max,
    35  	}
    36  	idr.base.Store(base)
    37  	return idr
    38  }
    39  
    40  // Next retrieves the next available ID.
    41  func (r *IDRange) Next() (int64, error) {
    42  	next := r.base.Add(1)
    43  	if next > r.max {
    44  		return 0, ErrIDExhaust
    45  	}
    46  	return next, nil
    47  }
    48  
    49  // AllocID allocates n IDs.
    50  func (sc *Context) AllocID(graph *catalog.Graph, n int) (*IDRange, error) {
    51  	graph.MDLock()
    52  	defer graph.MDUnlock()
    53  
    54  	var idRange *IDRange
    55  	err := kv.Txn(sc.store, func(txn kv.Transaction) error {
    56  		meta := meta.New(txn)
    57  		base, err := meta.AdvanceID(graph.Meta().ID, n)
    58  		if err != nil {
    59  			return err
    60  		}
    61  		idRange = NewIDRange(base, base+int64(n))
    62  		return nil
    63  	})
    64  
    65  	return idRange, err
    66  }