org.jclarion.clarion.util
Class FileState

java.lang.Object
  org.jclarion.clarion.util.FileState

public class FileState
extends java.lang.Object

Model state of JDBC Connection. This same object is used for current state and saved states

Author:

barney

Nested Class Summary

static class

FileState.Global

static class

FileState.Mode Read mode/state of the connection NONE - no reading occurring RESET - file/key is positioned but no reading yet FORWARD - we are reading forward BACK - we are reading backwards RESTORED - we have been restored file that was previously - either in Forward or Back mode, but we have not yet fully restored iterator position (iterator restore is lazy) USER - user defined SQL was executed

Field Summary

boolean[]	changed catalog of buffer columns that have been modified
int	currentLimit
boolean	disableBinding
ClarionObject[]	fields
FileState.Global	global
boolean	ignoreChange Ignore changes made to parameters as these are being done by internal ClarionFile object
boolean	isBounded
boolean[]	isnull catalog of buffer columns that have been flagged as null
boolean	keyBinding Key binding.
int	limit Limits - when scanning very large files say 10,000s of records in a browse, user usually only wants to see the first 20 or so.
ClarionMemoryChangeListener[]	listeners
FileState.Mode	mode
int	offset
SharedOutputStream	position Current scan position
ClarionKey	primaryKey Primary key and position
ClarionObject[]	primaryKeyFields
boolean	quickScan Quick scan has a comparable in original clarion.
ClarionObject	quickScanBuffer
boolean	quickScanResetActivated
int	readCount
java.sql.ResultSet	result
org.jclarion.clarion.util.FileState.ResultSetCount	resultSetCount
ClarionObject[]	scanFields
ClarionKey	scanKey Current scan key (if any)
java.lang.StringBuilder	select
java.sql.PreparedStatement	statement Current Result Set/etc
boolean	watchArmed is watch armed.
ClarionObject[]	watchBuffer Run following SQL before PUT() if expression fails then fail PUT().

Constructor Summary

FileState()

FileState(FileState.Global global)

FileState(FileState base)

Method Summary

void	closeCursor()
void	closeCursor(boolean clearKeyAndPosition)
void	closeCursor(boolean clearKeyAndPosition, boolean clearMode)
void	free()
int	getFieldIndex(ClarionObject o)
void	restore(FileState save)
FileState	save()
void	saveBuffer(SharedOutputStream target)
void	setKeyBinding(boolean b)
void	setLimit(int limit)

Methods inherited from class java.lang.Object

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

Field Detail

global

public FileState.Global global

mode

public FileState.Mode mode

fields

public ClarionObject[] fields

changed

public boolean[] changed

catalog of buffer columns that have been modified

isnull

public boolean[] isnull

catalog of buffer columns that have been flagged as null

statement

public java.sql.PreparedStatement statement

Current Result Set/etc

result

public java.sql.ResultSet result

resultSetCount

public org.jclarion.clarion.util.FileState.ResultSetCount resultSetCount

scanKey

public ClarionKey scanKey

Current scan key (if any)

scanFields

public ClarionObject[] scanFields

quickScanBuffer

public ClarionObject quickScanBuffer

primaryKey

public ClarionKey primaryKey

Primary key and position

primaryKeyFields

public ClarionObject[] primaryKeyFields

position

public SharedOutputStream position

Current scan position

ignoreChange

public boolean ignoreChange

Ignore changes made to parameters as these are being done by internal ClarionFile object

watchBuffer

public ClarionObject[] watchBuffer

Run following SQL before PUT() if expression fails then fail PUT(). Post PUT clear expression

watchArmed

public boolean watchArmed

is watch armed. If true On next read - set watch expression

listeners

public ClarionMemoryChangeListener[] listeners

select

public java.lang.StringBuilder select

limit

public int limit

Limits - when scanning very large files say 10,000s of records in a browse, user usually only wants to see the first 20 or so. Isntead of pulling back 10,000s of records per scan across JDBC - limit number of records to pull back. If limit is exhausted, then invisibly reset the scan to get the next block of records

currentLimit

public int currentLimit

readCount

public int readCount

offset

public int offset

keyBinding

public boolean keyBinding

Key binding. When using keys that are composite fields, it is very common that the program wants to 'fix' the first key and only scan second key. For example stock(franchise,partnum) - user may only want to look at parts in a given franchise But way clarion files work is that if I say all parts from franchise 2, partnum '1234' then all franchises above 2 are considered as well. When binding is in effect it works similar to limits. The initial query assumes that only franchise=2 is wanted. But if user executes 'next' statement beyond this then it will invisibly rewrite the query to handle this. This is beneficial in postgres at least because I had trouble getting postgres to optimise the following well franchise>2 OR (franchise=2 and partnum>='1234') Under some circumstances, instead of selecting a index scan starting at (2,'1234') sometimes postgrs would do a index scan at (2,) only - and filter records prior to 1234. For large data sets this can be very inefficient. But when I break it up into two queries i.e. a) franchise=2 and partnum>='1234' b) franchise>2 The system optimises quite well

isBounded

public boolean isBounded

disableBinding

public boolean disableBinding

quickScan

public boolean quickScan

Quick scan has a comparable in original clarion. Browse tables force reset when scrolling through parts instead of continuing to read the already established statement. Clearly this is inefficient. Clarion worked around this with a quickscan setting. What that setting does in clarion is unclear, documentation talks about 'buffering' which I assume is caching etc. For this implementation - quickScan merely intercepts key methods. Specifically: reset() - if resetting a scan that is already occurring in scan position matches the currently cached position - enable quickScan to continue to 'use' the existing scan

quickScanResetActivated

public boolean quickScanResetActivated

Constructor Detail

FileState

public FileState(FileState base)

FileState

public FileState()

FileState

public FileState(FileState.Global global)

Method Detail

closeCursor

public void closeCursor()

closeCursor

public void closeCursor(boolean clearKeyAndPosition)

closeCursor

public void closeCursor(boolean clearKeyAndPosition,
                        boolean clearMode)

free

public void free()

save

public FileState save()

saveBuffer

public void saveBuffer(SharedOutputStream target)

restore

public void restore(FileState save)

setLimit

public void setLimit(int limit)

setKeyBinding

public void setKeyBinding(boolean b)

getFieldIndex

public int getFieldIndex(ClarionObject o)