LogScanner Class Reference

Parses log records from a stream of binary data. More...

#include <log_consumer.h>

Public Member Functions
bool	nextLogrec (char *src, size_t &pos, logrec_t *&lr, lsn_t *nextLSN=nullptr, lsn_t *stopLSN=nullptr, int *lrLength=nullptr)
bool	hasPartialLogrec ()
void	reset ()
	LogScanner (size_t blockSize)
	~LogScanner ()
size_t	getBlockSize ()
void	setIgnore (logrec_t::kind_t type)
void	ignoreAll ()
void	unsetIgnore (logrec_t::kind_t type)
bool	isIgnored (logrec_t::kind_t type)

Private Attributes
size_t	truncCopied
size_t	truncMissing
size_t	toSkip
const size_t	blockSize
char *	truncBuf
bitset< logrec_t::t_max_logrec >	ignore

Detailed Description

Parses log records from a stream of binary data.

This class is not a scanner per se, as it does not perform any I/O. However, it enables efficient scanning by reading whole blocks of binary data from the recovery log and parsing log records from them using this class. This is an improvement over the traditional "scan" implemented in Shore-MT, which performs one random read for each log record. The major task implemented in this class is the control of block boundaries, which can occur in the middle of a log record (i.e., log records may spawn multiple blocks). To that end, it maintains an internal log record buffer to reconstruct such log records.

Log records are delivered via the nextLogrec() method, which takes the block address and offset within the block as parameters. Once the log record is parsed, the offset is updated (i.e., it is an output parameter). The method returns true if the log record was found entirely in the current block. Otherwise, it saves the partial data into its internal buffer and returns false, indicating to the caller that a new block must be provided. Upon invoking nextLogrec() once again, the caller then receives the complete log record.

Author

Caetano Sauer

Constructor & Destructor Documentation

LogScanner()

LogScanner::LogScanner ( size_t  blockSize )

inline

~LogScanner()

LogScanner::~LogScanner ( )

inline

Member Function Documentation

getBlockSize()

size_t LogScanner::getBlockSize ( )

inline

hasPartialLogrec()

bool LogScanner::hasPartialLogrec

(

)

ignoreAll()

void LogScanner::ignoreAll ( )

inline

isIgnored()

bool LogScanner::isIgnored ( logrec_t::kind_t  type )

inline

nextLogrec()

bool LogScanner::nextLogrec	(	char *	src,
		size_t &	pos,
		logrec_t *&	lr,
		lsn_t *	nextLSN = nullptr,
		lsn_t *	stopLSN = nullptr,
		int *	lrLength = nullptr
	)

Fetches a log record from the read buffer ('src' in offset 'pos'). Handles incomplete records due to block boundaries in the buffer and skips checkpoints and skip log records. Returns false if whole record could not be read in the current buffer block, indicating that the caller must fetch a new block into 'src' and invoke method again.

Method loops until any in-block skipping is completed.

reset()

void LogScanner::reset

(

)

setIgnore()

void LogScanner::setIgnore ( logrec_t::kind_t  type )

inline

unsetIgnore()

void LogScanner::unsetIgnore ( logrec_t::kind_t  type )

inline

Member Data Documentation

blockSize

const size_t LogScanner::blockSize

private

ignore

bitset<logrec_t::t_max_logrec> LogScanner::ignore

private

toSkip

size_t LogScanner::toSkip

private

truncBuf

char* LogScanner::truncBuf

private

truncCopied

size_t LogScanner::truncCopied

private

truncMissing

size_t LogScanner::truncMissing

private

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The documentation for this class was generated from the following files:

• src/sm/log_consumer.h
• src/sm/log_consumer.cpp