hbasescan查询代码分析

• client端ScannerCallable.call() -> close(scannerId)
• server端HRegionServer.close(scannerId)

• client端ScannerCallable.call() -> openScanner(regionName,scan)
• server端

• 创建RegionScanner
• 把scanner加入server的map集合
• 为新生成的scanner创建Lease

步骤2. ResultScanner.next()

• client端cache.poll() 或者 next(scannerId, caching)
• server端HRegionServer.next(scannerId,nbRows)

• RegionScannerImpl.nextRaw(List outResults, int limit, String metric)

Scanner的种类

• Server端InternalScanner ResultScanner
• 其他HFileScanner、MetaScanner

1. InternalScanner

• 是server端内部较高层次的scanner抽象实现类:
  • RegionScannerImpl
  • StoreScanner
  • KeyValueHeap
• 接口包括

• next()返回KeyValue List
• close()关闭scanner并释放server段资源

2. KeyValueScanner

• 是底层的scanner用来获取KeyValue实现类有
  • StoreScanner
  • StoreFileScanner
  • KeyValueHeap
  • NonLazyKeyValueScanner 每次都会做doRealSeek(forward)?reseek(kv):seek(kv);
  • MemStoreScanner
  • StoreScanner
  • KeyValueHeap
• 常用接口

• peek()
• next()
• seek() 定位到指定的KeyValue
• reseek() 从当前scanner位置之后的定位到KeyValue
• requestSeek()

KeyValueHeap

• 在Region层面用来组合访问多个store在Store层面用来组合访问memstore和storefiles
• PriorityQueue存储Scanner,KVScannerComparator对scanner进行排序先比较peak的kv再比较SequenceID
  • MemStoreScanner Long.MAX_VALUE
  • StoreFileScanner SequenceID
  • StoreScanner 0
• pollRealKV()从PriorityQueue中寻找可以做real seek的scanner

ScanQueryMatcher

• 在查找KV过程中确定是否包含当前KV以及接下来如何操作
• StoreScanner.getScanners(matcher) -> StoreFileScanner
• MatchCode的十种状态
  • INCLUDE
  • INCLUDE_AND_SEEK_NEXT_ROW : moreRowsMayExistAfter()getKeyForNextRow()
  • INCLUDE_AND_SEEK_NEXT_COL : getKeyForNextColumn()
  • DONE
  • DONE_SCAN
  • SEEK_NEXT_ROW : moreRowsMayExistAfter()
  • SEEK_NEXT_COL : getKeyForNextColumn()
  • SKIP : heap.next()
  • SEEK_NEXT_USING_HINT : getNextKeyHint()
  • NEXT(没用到): Do not include, jump to next StoreFile or memstore (in time order)
• public MatchCode match(KeyValue kv)
  • 比较是否是相同row
  • 比较版本是否过期
  • 检查是否被删除
  • 检查是否在time range
  • Filters过滤
  • ColumnTracker检查
• ColumnTracker
  • ScanWildcardColumnTracker
  • ExplicitColumnTracker
• DeleteTracker
  • ScanDeleteTracker
• 针对删除的查询策略

• retainDeletesInOutput
• keepDeletedCellstrue不会再做删除检查
• seePastDeleteMarkers