leveldb-Impl:VersionEdit.java

leveldb/VersionEdit.java at master · dain/leveldb · GitHub

public VersionEdit()
    {
    }

    public VersionEdit(Slice slice)
    {
        SliceInput sliceInput = slice.input();
        while (sliceInput.isReadable()) {
            int i = VariableLengthQuantity.readVariableLengthInt(sliceInput);
            VersionEditTag tag = VersionEditTag.getValueTypeByPersistentId(i);
            tag.readValue(sliceInput, this);
        }
    }

slice的长度和tag传入versionEdit

public String getComparatorName()
    {
        return comparatorName;
    }

    public void setComparatorName(String comparatorName)
    {
        this.comparatorName = comparatorName;
    }

    public Long getLogNumber()
    {
        return logNumber;
    }

    public void setLogNumber(long logNumber)
    {
        this.logNumber = logNumber;
    }

    public Long getNextFileNumber()
    {
        return nextFileNumber;
    }

    public void setNextFileNumber(long nextFileNumber)
    {
        this.nextFileNumber = nextFileNumber;
    }

    public Long getPreviousLogNumber()
    {
        return previousLogNumber;
    }

    public void setPreviousLogNumber(long previousLogNumber)
    {
        this.previousLogNumber = previousLogNumber;
    }

    public Long getLastSequenceNumber()
    {
        return lastSequenceNumber;
    }

    public void setLastSequenceNumber(long lastSequenceNumber)
    {
        this.lastSequenceNumber = lastSequenceNumber;
    }

维护LastSequence、PreviousLogNumber、NextFileNumber、ComparatorName等信息。

 public Map<Integer, InternalKey> getCompactPointers()
    {
        return ImmutableMap.copyOf(compactPointers);
    }

    public void setCompactPointer(int level, InternalKey key)
    {
        compactPointers.put(level, key);
    }

    public void setCompactPointers(Map<Integer, InternalKey> compactPointers)
    {
        this.compactPointers.putAll(compactPointers);
    }

维护CompactPointer的信息：level和Internal key，并定义批量处理操作。

 public Multimap<Integer, FileMetaData> getNewFiles()
    {
        return ImmutableMultimap.copyOf(newFiles);
    }

    // Add the specified file at the specified level.
    // REQUIRES: This version has not been saved (see VersionSet::SaveTo)
    // REQUIRES: "smallest" and "largest" are smallest and largest keys in file
    public void addFile(int level, long fileNumber,
            long fileSize,
            InternalKey smallest,
            InternalKey largest)
    {
        FileMetaData fileMetaData = new FileMetaData(fileNumber, fileSize, smallest, largest);
        addFile(level, fileMetaData);
    }

    public void addFile(int level, FileMetaData fileMetaData)
    {
        newFiles.put(level, fileMetaData);
    }

    public void addFiles(Multimap<Integer, FileMetaData> files)
    {
        newFiles.putAll(files);
    }

在一个level上Add文件，包括fileMetaData，InternalKey的smallest 和 largest范围

public Multimap<Integer, Long> getDeletedFiles()
    {
        return ImmutableMultimap.copyOf(deletedFiles);
    }

    // Delete the specified "file" from the specified "level".
    public void deleteFile(int level, long fileNumber)
    {
        deletedFiles.put(level, fileNumber);
    }

delete文件就是把要删除的文件的level和fileNumber放入deletedFiles中。

public Slice encode()
    {
        DynamicSliceOutput dynamicSliceOutput = new DynamicSliceOutput(4096);
        for (VersionEditTag versionEditTag : VersionEditTag.values()) {
            versionEditTag.writeValue(dynamicSliceOutput, this);
        }
        return dynamicSliceOutput.slice();
    }

对slice进行编码

@Override
    public String toString()
    {
        StringBuilder sb = new StringBuilder();
        sb.append("VersionEdit");
        sb.append("{comparatorName='").append(comparatorName).append('\'');
        sb.append(", logNumber=").append(logNumber);
        sb.append(", previousLogNumber=").append(previousLogNumber);
        sb.append(", lastSequenceNumber=").append(lastSequenceNumber);
        sb.append(", compactPointers=").append(compactPointers);
        sb.append(", newFiles=").append(newFiles);
        sb.append(", deletedFiles=").append(deletedFiles);
        sb.append('}');
        return sb.toString();
    }

转化为string