com.ziclix.python.sql

Class Fetch

java.lang.Object

com.ziclix.python.sql.Fetch

All Implemented Interfaces:

Traverseproc

public abstract class Fetch
extends java.lang.Object
implements Traverseproc

The responsibility of a Fetch instance is to manage the iteration of a ResultSet. Two different alogorithms are available: static or dynamic.

Static The static variety iterates the entire set immediately, creating the necessary Jython objects and storing them. It is able to immediately close the ResultSet so a call to close() is essentially a no-op from a database resource perspective (it does clear the results list however). This approach also allows for the correct rowcount to be determined since the entire result set has been iterated.

Dynamic The dynamic variety iterates the result set only as requested. This holds a bit truer to the intent of the API as the fetch*() methods actually fetch when instructed. This is especially useful for managing exeedingly large results, but is unable to determine the rowcount without having worked through the entire result set. The other disadvantage is the ResultSet remains open throughout the entire iteration. So the tradeoff is in open database resources versus JVM resources since the application can keep constant space if it doesn't require the entire result set be presented as one.

Field Summary

Fields

Modifier and Type	Field and Description
protected PyObject	description Field description
protected int	rowcount The total number of rows in the result set.
protected int	rownumber The current row of the cursor (-1 if off either end).

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Fetch(DataHandler datahandler) Constructor Fetch

Method Summary

Modifier and Type	Method and Description
abstract void	add(java.sql.CallableStatement callableStatement, Procedure procedure, PyObject params) Method add
abstract void	add(java.sql.ResultSet resultSet) Create the results after a successful execution and manages the result set.
abstract void	add(java.sql.ResultSet resultSet, java.util.Set<java.lang.Integer> skipCols) Create the results after a successful execution and manages the result set.
void	addWarningListener(WarningListener listener)
void	close() Cleanup any resources.
protected PyObject	createDescription(Procedure procedure) Builds a tuple containing the meta-information about each column.
protected PyObject	createDescription(java.sql.ResultSetMetaData meta) Builds a tuple containing the meta-information about each column.
protected PyTuple	createResult(java.sql.ResultSet set, java.util.Set<java.lang.Integer> skipCols, PyObject metaData) Creates the individual result row from the current ResultSet row.
protected PyObject	createResults(java.sql.CallableStatement callableStatement, Procedure procedure, PyObject params) Method createResults
protected PyList	createResults(java.sql.ResultSet set, java.util.Set<java.lang.Integer> skipCols, PyObject metaData) Creates the results of a query.
abstract PyObject	fetchall() Fetch all (remaining) rows of a query result, returning them as a sequence of sequences (e.g.
abstract PyObject	fetchmany(int size) Fetch the next set of rows of a query result, returning a sequence of sequences (e.g.
PyObject	fetchone() Fetch the next row of a query result set, returning a single sequence, or None when no more data is available.
protected void	fireWarning(java.sql.SQLWarning warning)
PyObject	getDescription() The description of each column, in order, for the data in the result set.
int	getRowCount() The number of rows in the current result set.
static Fetch	newFetch(DataHandler datahandler, boolean dynamic) Method newFetch
abstract PyObject	nextset() Move the result pointer to the next set if available.
boolean	refersDirectlyTo(PyObject ob) Optional operation.
boolean	removeWarningListener(WarningListener listener)
abstract void	scroll(int value, java.lang.String mode) Scroll the cursor in the result set to a new position according to mode.
int	traverse(Visitproc visit, java.lang.Object arg) Traverses all directly contained PyObjects.

Methods inherited from class java.lang.Object

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

Field Detail

rowcount

protected int rowcount

The total number of rows in the result set.

Note: since JDBC provides no means to get this information without iterating the entire result set, only those fetches which build the result statically will have an accurate row count.

rownumber

protected int rownumber

The current row of the cursor (-1 if off either end).

description

protected PyObject description

Field description

Constructor Detail

Fetch

protected Fetch(DataHandler datahandler)

Constructor Fetch

Parameters:

datahandler -

Method Detail

newFetch

public static Fetch newFetch(DataHandler datahandler,
                             boolean dynamic)

Method newFetch

Parameters:

datahandler -

dynamic -

Returns:

Fetch

getRowCount

public int getRowCount()

The number of rows in the current result set.

getDescription

public PyObject getDescription()

The description of each column, in order, for the data in the result set.

add

public abstract void add(java.sql.ResultSet resultSet)

Create the results after a successful execution and manages the result set.

Parameters:

resultSet -

add

public abstract void add(java.sql.ResultSet resultSet,
                         java.util.Set<java.lang.Integer> skipCols)

Create the results after a successful execution and manages the result set. Optionally takes a set of JDBC-indexed columns to automatically set to None primarily to support getTypeInfo() which sets a column type of a number but doesn't use the value so a driver is free to put anything it wants there.

Parameters:

resultSet -

skipCols - JDBC-indexed set of columns to be skipped

add

public abstract void add(java.sql.CallableStatement callableStatement,
                         Procedure procedure,
                         PyObject params)

Method add

Parameters:

callableStatement -

procedure -

params -

fetchone

public PyObject fetchone()

Fetch the next row of a query result set, returning a single sequence, or None when no more data is available.

An Error (or subclass) exception is raised if the previous call to executeXXX() did not produce any result set or no call was issued yet.

Returns:

a single sequence from the result set, or None when no more data is available

fetchall

public abstract PyObject fetchall()

Fetch all (remaining) rows of a query result, returning them as a sequence of sequences (e.g. a list of tuples). Note that the cursor's arraysize attribute can affect the performance of this operation.

An Error (or subclass) exception is raised if the previous call to executeXXX() did not produce any result set or no call was issued yet.

Returns:

a sequence of sequences from the result set, or None when no more data is available

fetchmany

public abstract PyObject fetchmany(int size)

Fetch the next set of rows of a query result, returning a sequence of sequences (e.g. a list of tuples). An empty sequence is returned when no more rows are available.

The number of rows to fetch per call is specified by the parameter. If it is not given, the cursor's arraysize determines the number of rows to be fetched. The method should try to fetch as many rows as indicated by the size parameter. If this is not possible due to the specified number of rows not being available, fewer rows may be returned.

An Error (or subclass) exception is raised if the previous call to executeXXX() did not produce any result set or no call was issued yet.

Note there are performance considerations involved with the size parameter. For optimal performance, it is usually best to use the arraysize attribute. If the size parameter is used, then it is best for it to retain the same value from one fetchmany() call to the next.

Returns:

a sequence of sequences from the result set, or None when no more data is available

nextset

public abstract PyObject nextset()

Move the result pointer to the next set if available.

Returns:

true if more sets exist, else None

scroll

public abstract void scroll(int value,
                            java.lang.String mode)

Scroll the cursor in the result set to a new position according to mode.

If mode is 'relative' (default), value is taken as offset to the current position in the result set, if set to 'absolute', value states an absolute target position.

An IndexError should be raised in case a scroll operation would leave the result set. In this case, the cursor position is left undefined (ideal would be to not move the cursor at all).

Note: This method should use native scrollable cursors, if available, or revert to an emulation for forward-only scrollable cursors. The method may raise NotSupportedErrors to signal that a specific operation is not supported by the database (e.g. backward scrolling).

Parameters:

value -

mode -

close

public void close()
           throws java.sql.SQLException

Cleanup any resources.

Throws:

java.sql.SQLException

createDescription

protected PyObject createDescription(java.sql.ResultSetMetaData meta)
                              throws java.sql.SQLException

Builds a tuple containing the meta-information about each column.

(name, type_code, display_size, internal_size, precision, scale, null_ok)

precision and scale are only available for numeric types

Throws:

java.sql.SQLException

createDescription

protected PyObject createDescription(Procedure procedure)
                              throws java.sql.SQLException

Builds a tuple containing the meta-information about each column.

(name, type_code, display_size, internal_size, precision, scale, null_ok)

precision and scale are only available for numeric types

Throws:

java.sql.SQLException

createResults

protected PyObject createResults(java.sql.CallableStatement callableStatement,
                                 Procedure procedure,
                                 PyObject params)
                          throws java.sql.SQLException

Method createResults

Parameters:

callableStatement -

procedure -

params -

Returns:

PyObject

Throws:

java.sql.SQLException

createResults

protected PyList createResults(java.sql.ResultSet set,
                               java.util.Set<java.lang.Integer> skipCols,
                               PyObject metaData)
                        throws java.sql.SQLException

Creates the results of a query. Iterates through the list and builds the tuple.

Parameters:

set - result set

skipCols - set of JDBC-indexed columns to automatically set to None

Returns:

a list of tuples of the results

Throws:

java.sql.SQLException

createResult

protected PyTuple createResult(java.sql.ResultSet set,
                               java.util.Set<java.lang.Integer> skipCols,
                               PyObject metaData)
                        throws java.sql.SQLException

Creates the individual result row from the current ResultSet row.

Parameters:

set - result set

skipCols - set of JDBC-indexed columns to automatically set to None

Returns:

a tuple of the results

Throws:

java.sql.SQLException

fireWarning

protected void fireWarning(java.sql.SQLWarning warning)

addWarningListener

public void addWarningListener(WarningListener listener)

removeWarningListener

public boolean removeWarningListener(WarningListener listener)

traverse

public int traverse(Visitproc visit,
                    java.lang.Object arg)

Description copied from interface: Traverseproc

Traverses all directly contained PyObjects. Like in CPython, arg must be passed unmodified to visit as its second parameter. If Visitproc.visit(PyObject, Object) returns nonzero, this return value must be returned immediately by traverse. Visitproc.visit(PyObject, Object) must not be called with a null PyObject-argument.

Specified by:

traverse in interface Traverseproc

refersDirectlyTo

public boolean refersDirectlyTo(PyObject ob)
                         throws java.lang.UnsupportedOperationException

Description copied from interface: Traverseproc

Optional operation. Should only be implemented if it is more efficient than calling Traverseproc.traverse(Visitproc, Object) with a visitproc that just watches out for ob. Must return false if ob is null.

Specified by:

refersDirectlyTo in interface Traverseproc

Throws:

java.lang.UnsupportedOperationException