Method logCheckpoint

src/java/simpledb/storage/LogFile.java:314–352

Checkpoint the log and write a checkpoint record.

()

    /** Checkpoint the log and write a checkpoint record. */
    public void logCheckpoint() throws IOException {
        //make sure we have buffer pool lock before proceeding
        synchronized (Database.getBufferPool()) {
            synchronized (this) {
                //Debug.log("CHECKPOINT, offset = " + raf.getFilePointer());
                preAppend();
                long startCpOffset, endCpOffset;
                Set<Long> keys = tidToFirstLogRecord.keySet();
                Iterator<Long> els = keys.iterator();
                force();
                Database.getBufferPool().flushAllPages();
                startCpOffset = raf.getFilePointer();
                raf.writeInt(CHECKPOINT_RECORD);
                raf.writeLong(-1); //no tid , but leave space for convenience

                //write list of outstanding transactions
                raf.writeInt(keys.size());
                while (els.hasNext()) {
                    Long key = els.next();
                    Debug.log("WRITING CHECKPOINT TRANSACTION ID: " + key);
                    raf.writeLong(key);
                    //Debug.log("WRITING CHECKPOINT TRANSACTION OFFSET: " + tidToFirstLogRecord.get(key));
                    raf.writeLong(tidToFirstLogRecord.get(key));
                }

                //once the CP is written, make sure the CP location at the
                // beginning of the log file is updated
                endCpOffset = raf.getFilePointer();
                raf.seek(0);
                raf.writeLong(startCpOffset);
                raf.seek(endCpOffset);
                raf.writeLong(currentOffset);
                currentOffset = raf.getFilePointer();
                //Debug.log("CP OFFSET = " + currentOffset);
            }
        }

        logTruncate();
    }

    /** Truncate any unneeded portion of the log to reduce its space
        consumption */