Package org.apache.hadoop.hbase.io.hfile

Interface HFileScanner

All Superinterfaces:
AutoCloseable, Closeable, Shipper
All Known Implementing Classes:
HFileReaderImpl.EncodedScanner, HFileReaderImpl.HFileScannerImpl
@Private public interface HFileScanner extends Shipper, Closeable
A scanner allows you to position yourself within a HFile and scan through it. It allows you to reposition yourself as well.

A scanner doesn't always have a key/value that it is pointing to when it is first created and before seekTo()/seekTo(Cell) are called. In this case, getKey()/getValue() returns null. At most other times, a key and value will be available. The general pattern is that you position the Scanner using the seekTo variants and then getKey and getValue.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    close()
    Close this HFile scanner and do necessary cleanup.
    Cell
    getCell()
    Returns Instance of Cell.
    Cell
    getKey()
    Gets the current key in the form of a cell.
    String
    getKeyString()
    Deprecated.
    Since hbase-2.0.0
    Cell
    getNextIndexedKey()
    Returns the next key in the index (the key to seek to the next block)
    HFile.Reader
    getReader()
    Returns Reader that underlies this Scanner instance.
    ByteBuffer
    getValue()
    Gets a buffer view to the current value.
    String
    getValueString()
    Deprecated.
    Since hbase-2.0.0
    boolean
    isSeeked()
     
    boolean
    next()
    Scans to the next entry in the file.
    void
    recordBlockSize(IntConsumer blockSizeConsumer)
    Record the size of the current block in bytes, passing as an argument to the blockSizeConsumer.
    int
    reseekTo(Cell cell)
    Reseek to or just before the passed cell.
    boolean
    seekBefore(Cell cell)
    Consider the cell stream of all the cells in the file, c[0] ..
    boolean
    seekTo()
    Positions this scanner at the start of the file.
    int
    seekTo(Cell cell)
    SeekTo or just before the passed cell.

    Methods inherited from interface org.apache.hadoop.hbase.regionserver.Shipper

    shipped

  • Method Details

    • seekTo

      int seekTo(Cell cell) throws IOException
      SeekTo or just before the passed cell. Examine the return code to figure whether we found the cell or not. Consider the cell stream of all the cells in the file, c[0] .. c[n], where there are n cells in the file.
      Returns:
      -1, if cell < c[0], no position; 0, such that c[i] = cell and scanner is left in position i; and 1, such that c[i] < cell, and scanner is left in position i. The scanner will position itself between c[i] and c[i+1] where c[i] < cell <= c[i+1]. If there is no cell c[i+1] greater than or equal to the input cell, then the scanner will position itself at the end of the file and next() will return false when it is called.
      Throws:
      IOException

    • reseekTo

      int reseekTo(Cell cell) throws IOException
      Reseek to or just before the passed cell. Similar to seekTo except that this can be called even if the scanner is not at the beginning of a file. This can be used to seek only to cells which come after the current position of the scanner. Consider the cell stream of all the cells in the file, c[0] .. c[n], where there are n cellc in the file after current position of HFileScanner. The scanner will position itself between c[i] and c[i+1] where c[i] < cell <= c[i+1]. If there is no cell c[i+1] greater than or equal to the input cell, then the scanner will position itself at the end of the file and next() will return false when it is called.
      Parameters:
      cell - Cell to find (should be non-null)
      Returns:
      -1, if cell < c[0], no position; 0, such that c[i] = cell and scanner is left in position i; and 1, such that c[i] < cell, and scanner is left in position i.
      Throws:
      IOException

    • seekBefore

      boolean seekBefore(Cell cell) throws IOException
      Consider the cell stream of all the cells in the file, c[0] .. c[n], where there are n cells in the file.
      Parameters:
      cell - Cell to find
      Returns:
      false if cell <= c[0] or true with scanner in position 'i' such that: c[i] < cell. Furthermore: there may be a c[i+1], such that c[i] < cell <= c[i+1] but there may also NOT be a c[i+1], and next() will return false (EOF).
      Throws:
      IOException

    • seekTo

      boolean seekTo() throws IOException
      Positions this scanner at the start of the file.
      Returns:
      False if empty file; i.e. a call to next would return false and the current key and value are undefined.
      Throws:
      IOException

    • next

      boolean next() throws IOException
      Scans to the next entry in the file.
      Returns:
      Returns false if you are at the end otherwise true if more in file.
      Throws:
      IOException

    • getKey

      Cell getKey()
      Gets the current key in the form of a cell. You must call seekTo(Cell) before this method.
      Returns:
      gets the current key as a Cell.

    • getValue

      ByteBuffer getValue()
      Gets a buffer view to the current value. You must call seekTo(Cell) before this method.
      Returns:
      byte buffer for the value. The limit is set to the value size, and the position is 0, the start of the buffer view.

    • getCell

      Cell getCell()
      Returns Instance of Cell.

    • getKeyString

      @Deprecated String getKeyString()
      Deprecated.
      Since hbase-2.0.0
      Convenience method to get a copy of the key as a string - interpreting the bytes as UTF8. You must call seekTo(Cell) before this method.
      Returns:
      key as a string

    • getValueString

      @Deprecated String getValueString()
      Deprecated.
      Since hbase-2.0.0
      Convenience method to get a copy of the value as a string - interpreting the bytes as UTF8. You must call seekTo(Cell) before this method.
      Returns:
      value as a string

    • getReader

      HFile.Reader getReader()
      Returns Reader that underlies this Scanner instance.

    • isSeeked

      boolean isSeeked()
      Returns:
      True is scanner has had one of the seek calls invoked; i.e. seekBefore(Cell) or seekTo() or seekTo(Cell). Otherwise returns false.

    • getNextIndexedKey

      Cell getNextIndexedKey()
      Returns the next key in the index (the key to seek to the next block)

    • close

      void close()
      Close this HFile scanner and do necessary cleanup.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable

    • recordBlockSize

      void recordBlockSize(IntConsumer blockSizeConsumer)
      Record the size of the current block in bytes, passing as an argument to the blockSizeConsumer. Implementations should ensure that blockSizeConsumer is only called once per block.
      Parameters:
      blockSizeConsumer - to be called with block size in bytes, once per block.