uk.ac.starlink.table.jdbc

Class JDBCStarTable

java.lang.Object

uk.ac.starlink.table.AbstractStarTable

uk.ac.starlink.table.jdbc.JDBCStarTable

All Implemented Interfaces:

Closeable, AutoCloseable, StarTable

public class JDBCStarTable
extends AbstractStarTable

A StarTable implementation based on the results of an SQL query on a JDBC table.

Constructor Summary

Constructors

Constructor and Description
JDBCStarTable(Connector connx, String sql) Constructs a StarTable representing the data returned by an SQL query using a JDBC connections from a given source, with sequential access only.
JDBCStarTable(Connector connx, String sql, boolean isRandom) Constructs a StarTable representing the data returned by an SQL query using JDBC connections from a given source, optionally providing random access.

Method Summary

Modifier and Type	Method and Description
Object	getCell(long lrow, int icol) The AbstractStarTable implementation of this method throws an UnsupportedOperationException, since unless otherwise provided there is no random access.
List<ValueInfo>	getColumnAuxDataInfos() Goes through the table columns (ColumnInfo objects) and picks out all the AuxData items which exist, generalising where necessary and returning a union of them in alphabetical order by name.
int	getColumnCount() Returns the number of columns in this table.
ColumnInfo	getColumnInfo(int icol) Returns the object describing the data in a given column.
Connection	getConnection() Returns a JDBC Connection that can supply the data for this table.
Object[]	getRow(long lrow) The AbstractStarTable implementation of this method constructs a row by repeated invocation of AbstractStarTable.getCell(long, int).
RowAccess	getRowAccess() Returns an object which can provide random access to this table's data, if random access is implemented.
long	getRowCount() Returns the number of rows in this table, if known.
RowSequence	getRowSequence() Returns an object which can iterate over all the rows in the table sequentially.
String	getSql() Returns the text of the SQL query used for this table.
boolean	isRandom() The AbstractStarTable implementation of this method returns false.
void	setRandom() Ensures that this table provides random access.

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

checkedLongToInt, close, getName, getParameters, getRowSplittable, getURL, 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

Constructor Detail

JDBCStarTable

public JDBCStarTable(Connector connx,
                     String sql)
              throws SQLException

Constructs a StarTable representing the data returned by an SQL query using a JDBC connections from a given source, with sequential access only.

Parameters:

connx - object which can supply JDBC connections

sql - text of the SQL query

Throws:

SQLException

JDBCStarTable

public JDBCStarTable(Connector connx,
                     String sql,
                     boolean isRandom)
              throws SQLException

Constructs a StarTable representing the data returned by an SQL query using JDBC connections from a given source, optionally providing random access.

This was initially written to take a Connection rather than a Connector object, but it seems that there are limits to the number of ResultSets that can be simultaneously open on a Connection.

Parameters:

connx - object which can supply JDBC connections

sql - text of the SQL query

isRandom - whether this table needs to provide random access or not (there are costs associated with this)

Throws:

SQLException

Method Detail

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

getColumnAuxDataInfos

public List<ValueInfo> getColumnAuxDataInfos()

Description copied from class: AbstractStarTable

Goes through the table columns (ColumnInfo objects) and picks out all the AuxData items which exist, generalising where necessary and returning a union of them in alphabetical order by name. Subclasses should override this if they can do better, for instance providing an order for the keys.

Specified by:

getColumnAuxDataInfos in interface StarTable

Overrides:

getColumnAuxDataInfos in class AbstractStarTable

Returns:

a list of all the auxiliary metadata ValueInfo items which in fact crop up in column metadata

See Also:

DefaultValueInfo.getAuxData()

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

setRandom

public void setRandom()
               throws SQLException

Ensures that this table provides random access. Following this call the isRandom method will return true. Calling this method multiple times is harmless.

Throws:

SQLException

isRandom

public boolean isRandom()

Description copied from class: AbstractStarTable

The AbstractStarTable implementation of this method returns false.

Specified by:

isRandom in interface StarTable

Overrides:

isRandom in class AbstractStarTable

Returns:

true if table random access methods are available

getCell

public Object getCell(long lrow,
                      int icol)
               throws IOException

Description copied from class: AbstractStarTable

The AbstractStarTable implementation of this method throws an UnsupportedOperationException, since unless otherwise provided there is no random access.

Specified by:

getCell in interface StarTable

Overrides:

getCell in class AbstractStarTable

Parameters:

lrow - the index of the cell's row

icol - the index of the cell's column

Returns:

the contents of this cell

Throws:

IOException - if there is an error reading the data

getRow

public Object[] getRow(long lrow)
                throws IOException

Description copied from class: AbstractStarTable

The AbstractStarTable implementation of this method constructs a row by repeated invocation of AbstractStarTable.getCell(long, int).

Specified by:

getRow in interface StarTable

Overrides:

getRow in class AbstractStarTable

Parameters:

lrow - the index of the row to retrieve

Returns:

an array of the objects in each cell in row irow

Throws:

IOException - if there is an error reading the data

getRowAccess

public RowAccess getRowAccess()
                       throws IOException

Description copied from interface: StarTable

Returns an object which can provide random access to this table's data, if random access is implemented. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowAccess in interface StarTable

Overrides:

getRowAccess in class AbstractStarTable

Returns:

new RowAccess

Throws:

IOException - if there is an error setting up access

getRowSequence

public RowSequence getRowSequence()
                           throws IOException

Description copied from interface: StarTable

Returns an object which can iterate over all the rows in the table sequentially. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowSequence in interface StarTable

Specified by:

getRowSequence in class AbstractStarTable

Returns:

new RowSequence

Throws:

IOException - if there is an error providing access

getConnection

public Connection getConnection()
                         throws SQLException

Returns a JDBC Connection that can supply the data for this table.

Returns:

a JDBC Connection object

Throws:

SQLException

getSql

public String getSql()

Returns the text of the SQL query used for this table.

Returns:

the SQL query text