uk.ac.starlink.parquet

Class ParquetStarTable

java.lang.Object

uk.ac.starlink.table.AbstractStarTable

uk.ac.starlink.parquet.ParquetStarTable

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, StarTable

Direct Known Subclasses:

CachedParquetStarTable, SequentialParquetStarTable

public abstract class ParquetStarTable
extends AbstractStarTable

Partial StarTable implementation based on a Parquet file. This class provides metadata handling and preparation for data reading, but does not implement actual data access methods.

Since:

25 Feb 2021

Field Summary

Fields

Modifier and Type	Field and Description
static ValueInfo	CREATEDBY_INFO Parameter metadata for parquet creation info.

Constructor Summary

Constructors

Constructor and Description
ParquetStarTable(IOSupplier<ParquetFileReader> pfrSupplier) Constructor.

Method Summary

Modifier and Type	Method and Description
int	getColumnCount() Returns the number of columns in this table.
ColumnInfo	getColumnInfo(int icol) Returns the object describing the data in a given column.
ColumnReadStore	getColumnReadStore(PageReadStore pageStore, MessageType schema) Gets a ColumnReadStore from a PageReadStore.
InputColumn<?>	getInputColumn(int icol) Returns the input column that can be used to read a given column of this table.
ParquetFileReader	getParquetFileReader() Returns a reader for this table's underlying file.
long	getRowCount() Returns the number of rows in this table, if known.
MessageType	getSchema() Returns the schema of the the parquet file.

Methods inherited from class uk.ac.starlink.table.AbstractStarTable

checkedLongToInt, close, getCell, getColumnAuxDataInfos, getName, getParameters, getRow, getRowAccess, getRowSequence, getRowSplittable, getURL, isRandom, setName, setParameters, setURL

Methods inherited from class java.lang.Object

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

Methods inherited from interface uk.ac.starlink.table.StarTable

getParameterByName, setParameter

Field Detail

CREATEDBY_INFO

public static final ValueInfo CREATEDBY_INFO

Parameter metadata for parquet creation info.

Constructor Detail

ParquetStarTable

public ParquetStarTable(IOSupplier<ParquetFileReader> pfrSupplier)
                 throws java.io.IOException

Constructor.

Parameters:

pfrSupplier - access to parquet data file

Throws:

java.io.IOException

Method Detail

getColumnCount

public int getColumnCount()

Description copied from interface: StarTable

Returns the number of columns in this table.

Specified by:

getColumnCount in interface StarTable

Specified by:

getColumnCount in class AbstractStarTable

Returns:

the number of columns

getRowCount

public long getRowCount()

Description copied from interface: StarTable

Returns the number of rows in this table, if known. If the number of rows cannot be (easily) determined, a value of -1 will be returned.

Specified by:

getRowCount in interface StarTable

Specified by:

getRowCount in class AbstractStarTable

Returns:

the number of rows, or -1

getColumnInfo

public ColumnInfo getColumnInfo(int icol)

Description copied from interface: StarTable

Returns the object describing the data in a given column.

Specified by:

getColumnInfo in interface StarTable

Specified by:

getColumnInfo in class AbstractStarTable

Parameters:

icol - the column for which header information is required

Returns:

a ValueInfo object for column icol

getParquetFileReader

public ParquetFileReader getParquetFileReader()
                                       throws java.io.IOException

Returns a reader for this table's underlying file.

Returns:

parquet file reader

Throws:

java.io.IOException

getSchema

public MessageType getSchema()

Returns the schema of the the parquet file.

Returns:

parquet schema

getColumnReadStore

public ColumnReadStore getColumnReadStore(PageReadStore pageStore,
                                          MessageType schema)

Gets a ColumnReadStore from a PageReadStore.

Parameters:

pageStore - page store

schema - schema for required data; this may for instance define only a subset of available columns

Returns:

column store

getInputColumn

public InputColumn<?> getInputColumn(int icol)

Returns the input column that can be used to read a given column of this table.

Parameters:

icol - column index

Returns:

input column