FileReader (starrocks-bdb-je 18.3.17 API)

java.lang.Object
- com.sleepycat.je.log.FileReader

Direct Known Subclasses:

CheckpointFileReader, CleanerFileReader, DumpFileReader, FeederReader, FeederSyncupReader, INFileReader, LastFileReader, LNFileReader, ReplicaSyncupReader, ScavengerFileReader, SearchFileReader, UtilizationFileReader
```
public abstract class FileReader
extends Object
```
A FileReader is an abstract class that traverses the log files, reading-in chunks of the file at a time. The class provides a iterator interface, via its readNextEntry() method. Concrete subclasses must (a) provide the public methods that allow their users to examine the contents of the logrec that the iterator is currently positioned at, and (b) implement the (non-public) isTarget() and processEntry() methods that may filter-out logrecs that do not need to be seen by the caller of readNextEntry(), or perform specific actions before each logrec is "returned" to the caller of readNextEntry().

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`FileReader.EOFException` Never seen by user, used to indicate that the file reader should stop.
`protected static class`	`FileReader.ReadWindow` A ReadWindow provides a swath of data read from the JE log.

Field Summary

Fields
Modifier and Type	Field and Description
`protected ChecksumValidator`	`cksumValidator`
`protected LogEntryHeader`	`currentEntryHeader`
`protected long`	`currentEntryOffset`
`protected long`	`currentEntryPrevOffset`
`protected EnvironmentImpl`	`envImpl`
`protected boolean`	`eof`
`protected FileManager`	`fileManager`
`protected boolean`	`forward`
`protected Logger`	`logger`
`protected long`	`nextEntryOffset`
`protected long`	`startLsn`
`protected FileReader.ReadWindow`	`window`

Constructor Summary

Constructors
Constructor and Description
`FileReader(EnvironmentImpl envImpl, int readBufferSize, boolean forward, long startLsn, Long singleFileNumber, long endOfFileLsn, long finishLsn)`
`FileReader(EnvironmentImpl envImpl, int readBufferSize, boolean forward, long startLsn, Long singleFileNumber, long endOfFileLsn, long finishLsn, boolean doChecksumOnRead)`

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`entryIsReplicated()`
`int`	`getAndResetNReads()` Returns the number of reads since the last time this method was called.
`int`	`getLastEntrySize()` Returns the total size (including header) of the last entry read.
`long`	`getLastLsn()` Get LSN of the last entry read.
`VLSN`	`getLastVlsn()` Returns the VLSN of the last entry read, or null if the entry has no VLSN (not replicated and has no migrated VLSN).
`int`	`getLogVersion()` Returns the log version of the last entry read.
`long`	`getNRepeatIteratorReads()`
`int`	`getNumRead()`
`protected void`	`handleGapInBackwardsScan(long prevFileNum)` TBW
`protected void`	`initStartingPosition(long endOfFileLsn, Long ignoreSingleFileNumber)` Helper for determining the starting position and opening up a file at the desired location.
`protected boolean`	`isTargetEntry()` This method is called by readNextEntry() after the header of the current logrec has been de-serialized, but not the body.
`protected FileReader.ReadWindow`	`makeWindow(int readBufferSize)` May be overridden by other FileReaders.
`protected abstract boolean`	`processEntry(ByteBuffer entryBuffer)` Each file reader implements this method to process the entry data.
`boolean`	`readNextEntry()` Scans the log files until either it has reached the end of the log or has hit an invalid portion.
`boolean`	`readNextEntryAllowExceptions()` Variant of readNextEntry that throws FileNotFoundException and ChecksumException, rather than wrapping them in an EnvironmentFailureException and invalidating the enviornment.
`void`	`setAlwaysValidateChecksum(boolean validate)` Whether to always validate the checksum, even for non-target entries.
`protected void`	`setBackwardPosition()` Ensure that the next target is in the window.
`protected void`	`setForwardPosition()` Ensure that the next target is in the window.
`void`	`skipData(int amountToSkip)`
`protected void`	`skipEntry(ByteBuffer entryBuffer)` May be called by processEntry when it determines that the entry does not need to be read/de-serialized.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - envImpl
```
protected final EnvironmentImpl envImpl
```
  - fileManager
```
protected final FileManager fileManager
```
  - window
```
protected final FileReader.ReadWindow window
```
  - eof
```
protected boolean eof
```
  - forward
```
protected final boolean forward
```
  - currentEntryHeader
```
protected LogEntryHeader currentEntryHeader
```
  - currentEntryPrevOffset
```
protected long currentEntryPrevOffset
```
  - currentEntryOffset
```
protected long currentEntryOffset
```
  - nextEntryOffset
```
protected long nextEntryOffset
```
  - startLsn
```
protected long startLsn
```
  - cksumValidator
```
protected ChecksumValidator cksumValidator
```
  - logger
```
protected final Logger logger
```
- Constructor Detail
  - FileReader
```
public FileReader(EnvironmentImpl envImpl,
                  int readBufferSize,
                  boolean forward,
                  long startLsn,
                  Long singleFileNumber,
                  long endOfFileLsn,
                  long finishLsn)
           throws DatabaseException
```
    Throws:
    
    DatabaseException
  - FileReader
```
public FileReader(EnvironmentImpl envImpl,
                  int readBufferSize,
                  boolean forward,
                  long startLsn,
                  Long singleFileNumber,
                  long endOfFileLsn,
                  long finishLsn,
                  boolean doChecksumOnRead)
           throws DatabaseException
```
    Throws:
    
    DatabaseException
- Method Detail
  - makeWindow
```
protected FileReader.ReadWindow makeWindow(int readBufferSize)
                                    throws DatabaseException
```
    May be overridden by other FileReaders.
    
    Throws:
    
    DatabaseException
  - initStartingPosition
```
protected void initStartingPosition(long endOfFileLsn,
                                    Long ignoreSingleFileNumber)
```
    Helper for determining the starting position and opening up a file at the desired location.
  - setAlwaysValidateChecksum
```
public void setAlwaysValidateChecksum(boolean validate)
```
    Whether to always validate the checksum, even for non-target entries.
  - getNumRead
```
public int getNumRead()
```
    Returns:
    
    the number of entries processed by this reader.
  - getNRepeatIteratorReads
```
public long getNRepeatIteratorReads()
```
  - getLastLsn
```
public long getLastLsn()
```
    Get LSN of the last entry read.
  - getLastVlsn
```
public VLSN getLastVlsn()
```
    Returns the VLSN of the last entry read, or null if the entry has no VLSN (not replicated and has no migrated VLSN).
  - getLastEntrySize
```
public int getLastEntrySize()
```
    Returns the total size (including header) of the last entry read.
  - getLogVersion
```
public int getLogVersion()
```
    Returns the log version of the last entry read.
  - readNextEntry
```
public boolean readNextEntry()
```
    Scans the log files until either it has reached the end of the log or has hit an invalid portion.
    
    Returns:
    
    true if an element has been read, false at end-of-log.
    
    Throws:
    
    EnvironmentFailureException - if a ChecksumException, FileNotFoundException, or another internal problem occurs.
  - readNextEntryAllowExceptions
```
public final boolean readNextEntryAllowExceptions()
                                           throws FileNotFoundException,
                                                  ChecksumException
```
    Variant of readNextEntry that throws FileNotFoundException and ChecksumException, rather than wrapping them in an EnvironmentFailureException and invalidating the enviornment. This allows users of this class (see cleaner.FileProcessor), and subclasses that override readNextEntry (see ScavengerFileReader and LastFileReader), to handle these exceptions specially.
    
    Throws:
    
    FileNotFoundException
    
    ChecksumException
  - skipEntry
```
protected void skipEntry(ByteBuffer entryBuffer)
```
    May be called by processEntry when it determines that the entry does not need to be read/de-serialized.
  - setForwardPosition
```
protected void setForwardPosition()
                           throws FileReader.EOFException,
                                  DatabaseException,
                                  ChecksumException,
                                  FileNotFoundException
```
    Ensure that the next target is in the window. The default behavior is that the next target is the next, following entry, so we can assume that it's in the window. All we have to do is to check if we've gone past the specified end point.
    
    Throws:
    
    DatabaseException
    
    FileNotFoundException
    
    ChecksumException
    
    FileReader.EOFException
  - setBackwardPosition
```
protected void setBackwardPosition()
                            throws ChecksumException,
                                   FileNotFoundException,
                                   FileReader.EOFException,
                                   DatabaseException
```
    Ensure that the next target is in the window. The default behavior is that the next target is the next previous entry.
    
    Throws:
    
    DatabaseException
    
    ChecksumException
    
    FileNotFoundException
    
    FileReader.EOFException
  - skipData
```
public void skipData(int amountToSkip)
              throws ChecksumException,
                     FileReader.EOFException,
                     FileNotFoundException,
                     DatabaseException
```
    Throws:
    
    ChecksumException
    
    FileReader.EOFException
    
    FileNotFoundException
    
    DatabaseException
  - getAndResetNReads
```
public int getAndResetNReads()
```
    Returns the number of reads since the last time this method was called.
  - isTargetEntry
```
protected boolean isTargetEntry()
                         throws DatabaseException
```
    This method is called by readNextEntry() after the header of the current logrec has been de-serialized, but not the body. Based on header info only, it may perform some actions and then decide whether the rest of the logrec should be de-serialized or just skipped.
    
    Returns:
    
    true if this reader should process the current logrec further, via the processEntry() method. A logrec must be passed to processEntry if the full logrec (not just the header) must be de-serialized for further processing. Return false if no further processing is needed, in which case the current logrec will be skipped (i.e, not returned to the caller of readNextEntry().
    
    Throws:
    
    DatabaseException - from subclasses.
  - processEntry
```
protected abstract boolean processEntry(ByteBuffer entryBuffer)
                                 throws DatabaseException
```
    Each file reader implements this method to process the entry data.
    
    Parameters:
    
    entryBuffer - A ByteBuffer that the logrec data and is positioned at the start of the logrec body (i.e., just after the logrec header).
    
    Returns:
    
    true if this entry should be returned to the caller of readNextEntry().
    
    Throws:
    
    DatabaseException
  - entryIsReplicated
```
public boolean entryIsReplicated()
```
    Returns:
    
    true if the current entry is part of replication stream.
  - handleGapInBackwardsScan
```
protected void handleGapInBackwardsScan(long prevFileNum)
```
    TBW

Class FileReader

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

envImpl

fileManager

window

eof

forward

currentEntryHeader

currentEntryPrevOffset

currentEntryOffset

nextEntryOffset

startLsn

cksumValidator

logger

Constructor Detail

FileReader

FileReader

Method Detail

makeWindow

initStartingPosition

setAlwaysValidateChecksum

getNumRead

getNRepeatIteratorReads

getLastLsn

getLastVlsn

getLastEntrySize

getLogVersion

readNextEntry

readNextEntryAllowExceptions

skipEntry

setForwardPosition

setBackwardPosition

skipData

getAndResetNReads

isTargetEntry

processEntry

entryIsReplicated

handleGapInBackwardsScan