Package edu.caltech.nanodb.storage

Class StatsWriter

java.lang.Object

edu.caltech.nanodb.storage.StatsWriter

public class StatsWriter
extends java.lang.Object

This class encapsulates the operations of reading and writing table-statistics to a data file.

Field Summary

Fields

Modifier and Type	Field	Description
private static int	COLSTAT_NULLMASK_MAX_VALUE	A bit-mask used for storing column-stats, to record whether or not the "maximum value" value is present for the column.
private static int	COLSTAT_NULLMASK_MIN_VALUE	A bit-mask used for storing column-stats, to record whether or not the "minimum value" value is present for the column.
private static int	COLSTAT_NULLMASK_NUM_DISTINCT_VALUES	A bit-mask used for storing column-stats, to record whether or not the "number of distinct values" value is present for the column.
private static int	COLSTAT_NULLMASK_NUM_NULL_VALUES	A bit-mask used for storing column-stats, to record whether or not the "number of NULL values" value is present for the column.
private static org.apache.logging.log4j.Logger	logger	A logging object for reporting anything interesting that happens.

Constructor Summary

Constructors

Modifier	Constructor	Description
private	StatsWriter()

Method Summary

Modifier and Type	Method	Description
static TableStats	readTableStats(PageReader pgReader, Schema schema)	Reads the table-statistics from the specified data file.
static void	writeTableStats(Schema schema, TableStats stats, PageWriter pgWriter)	Writes the specified table-statistics to a data file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

logger

private static org.apache.logging.log4j.Logger logger

A logging object for reporting anything interesting that happens.

COLSTAT_NULLMASK_NUM_DISTINCT_VALUES

private static final int COLSTAT_NULLMASK_NUM_DISTINCT_VALUES

A bit-mask used for storing column-stats, to record whether or not the "number of distinct values" value is present for the column.

See Also:

Constant Field Values

COLSTAT_NULLMASK_NUM_NULL_VALUES

private static final int COLSTAT_NULLMASK_NUM_NULL_VALUES

A bit-mask used for storing column-stats, to record whether or not the "number of NULL values" value is present for the column.

See Also:

Constant Field Values

COLSTAT_NULLMASK_MIN_VALUE

private static final int COLSTAT_NULLMASK_MIN_VALUE

A bit-mask used for storing column-stats, to record whether or not the "minimum value" value is present for the column.

See Also:

Constant Field Values

COLSTAT_NULLMASK_MAX_VALUE

private static final int COLSTAT_NULLMASK_MAX_VALUE

A bit-mask used for storing column-stats, to record whether or not the "maximum value" value is present for the column.

See Also:

Constant Field Values

Constructor Detail

StatsWriter

private StatsWriter()

Method Detail

writeTableStats

public static void writeTableStats(Schema schema,
                                   TableStats stats,
                                   PageWriter pgWriter)

Writes the specified table-statistics to a data file.

Parameters:

schema - the schema of the table

stats - the statistics to save for the table

pgWriter - a page-writer specifying where the data should be written to

readTableStats

public static TableStats readTableStats(PageReader pgReader,
                                        Schema schema)

Reads the table-statistics from the specified data file.

Parameters:

pgReader - a page-reader specifying where the data should be read from

schema - the schema of the table

Returns:

the table statistics loaded from the file