org.apache.derby.impl.sql.execute
Class ScanResultSet

java.lang.Object
  org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl
      org.apache.derby.impl.sql.execute.NoPutResultSetImpl
          org.apache.derby.impl.sql.execute.ScanResultSet

All Implemented Interfaces:

NoPutResultSet, ResultSet, RowLocationRetRowSource, RowSource

Direct Known Subclasses:

DependentResultSet, HashScanResultSet, LastIndexKeyResultSet, TableScanResultSet

abstract class ScanResultSet
extends NoPutResultSetImpl

Abstract ResultSet class for NoPutResultSets which contain a scan. Returns rows that may be a column sub-set of the rows in the underlying object to be scanned. If accessedCols is not null then a sub-set of columns will be fetched from the underlying object (usually into the candidate row object), then the returned rows will be a compacted form of that row, with the not-fetched columns moved out. If accessedCols is null then the full row will be returned.
Example: if accessedCols indicates that we want to retrieve columns 1 and 4, then candidate row will have space for 5 columns (because that's the size of the rows in the underlying object), but only cols "1" and "4" will have values:

     0    1    2    3    4
  [  - , COL1,  - ,  - , COL4 ]
  

Rows returned by this ScanResultSet will have the values:

     0     1
  [ COL1, COL4 ]
 

Field Summary

protected FormatableBitSet	accessedCols If not null indicates the subset of columns that need to be pulled from the underlying object to be scanned.
(package private) ExecRow	candidate The candidate row, matches the shape of the rows in the underlying object to be scanned.
(package private) int	isolationLevel The scan isolation level.
private boolean	isolationLevelNeedsUpdate Tells whether the isolation level needs to be updated.
(package private) int	lockMode The actual lock mode used.
(package private) ExecRowBuilder	resultRowBuilder Object used to create and reset the candidate row.
private int	suppliedLockMode The lock mode supplied through the constructor.
private boolean	tableLocked If true, the table is marked as table locked in SYS.SYSTABLES.
private boolean	unspecifiedIsolationLevel If true, the isolation level is unspecified and must be refreshed on each open.

Fields inherited from class org.apache.derby.impl.sql.execute.NoPutResultSetImpl

checkNullCols, clonedExecRow, cncLen, resultSetNumber, targetResultSet

Fields inherited from class org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl

activation, beginTime, closeTime, compactRow, constructorTime, currentRow, endExecutionTime, finished, isOpen, isTopResultSet, nextTime, numOpens, openTime, optimizerEstimatedCost, optimizerEstimatedRowCount, resultDescription, rowsFiltered, rowsSeen, startExecutionTime, subqueryTrackingArray

Fields inherited from interface org.apache.derby.iapi.sql.execute.NoPutResultSet

ABSOLUTE, FIRST, LAST, NEXT, PREVIOUS, RELATIVE

Fields inherited from interface org.apache.derby.iapi.sql.ResultSet

CURRENT_RESULTSET_ONLY, ENTIRE_RESULTSET_TREE, ISAFTERLAST, ISBEFOREFIRST, ISFIRST, ISLAST

Constructor Summary

ScanResultSet(Activation activation, int resultSetNumber, int resultRowTemplate, int lockMode, boolean tableLocked, int isolationLevel, int colRefItem, double optimizerEstimatedRowCount, double optimizerEstimatedCost)
Construct a ScanResultSet.

Method Summary

(package private) abstract boolean	canGetInstantaneousLocks() Can we get instantaneous locks when getting share row locks at READ COMMITTED.
void	close() Close the result set.
private int	getLockMode(int languageLevel) Get the lock mode based on the language isolation level.
int	getScanIsolationLevel() Return the isolation level of the scan in the result set.
(package private) void	initIsolationLevel() Initialize the isolation level and the lock mode.
private int	translateLanguageIsolationLevel(int languageLevel) Translate isolation level from language to store.

Methods inherited from class org.apache.derby.impl.sql.execute.NoPutResultSetImpl

clearCurrentRow, clearOrderableCache, closeRowSource, getCursorName, getNextRowFromRowSource, getResultDescription, getValidColumns, isForUpdate, markRowAsDeleted, needsRowLocation, needsToClone, positionScanAtRowLocation, printQualifiers, resultSetNumber, rowLocation, setCurrentRow, setNeedsRowLocation, setTargetResultSet, skipRow, skipScan, updateRow

Methods inherited from class org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl

addWarning, attachStatementContext, checkCancellationFlag, checkRowPosition, cleanUp, dumpTimeStats, finish, finishAndRTS, getAbsoluteRow, getActivation, getAutoGeneratedKeysResultset, getBeginExecutionTimestamp, getCompactRow, getCurrentTimeMillis, getElapsedMillis, getEndExecutionTimestamp, getEstimatedRowCount, getExecuteTime, getExecutionFactory, getFirstRow, getLanguageConnectionContext, getLastRow, getNextRow, getNextRowCore, getPointOfAttachment, getPreviousRow, getRelativeRow, getRowNumber, getSubqueryTrackingArray, getTransactionController, getWarnings, isClosed, markAsTopResultSet, modifiedRowCount, open, recordConstructorTime, reopenCore, requiresRelocking, returnsRows, setAfterLastRow, setBeforeFirstRow, setCompactRow, setCompatRow

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.derby.iapi.sql.execute.NoPutResultSet

openCore

Methods inherited from interface org.apache.derby.iapi.sql.ResultSet

getTimeSpent

Field Detail

tableLocked

private final boolean tableLocked

If true, the table is marked as table locked in SYS.SYSTABLES.

unspecifiedIsolationLevel

private final boolean unspecifiedIsolationLevel

If true, the isolation level is unspecified and must be refreshed on each open.

suppliedLockMode

private final int suppliedLockMode

The lock mode supplied through the constructor.

isolationLevelNeedsUpdate

private boolean isolationLevelNeedsUpdate

Tells whether the isolation level needs to be updated.

lockMode

int lockMode

The actual lock mode used.

isolationLevel

int isolationLevel

The scan isolation level.

resultRowBuilder

final ExecRowBuilder resultRowBuilder

Object used to create and reset the candidate row.

candidate

final ExecRow candidate

The candidate row, matches the shape of the rows in the underlying object to be scanned.

accessedCols

protected final FormatableBitSet accessedCols

If not null indicates the subset of columns that need to be pulled from the underlying object to be scanned. Set from the PreparedStatement's saved objects, if it exists.

Constructor Detail

ScanResultSet

ScanResultSet(Activation activation,
              int resultSetNumber,
              int resultRowTemplate,
              int lockMode,
              boolean tableLocked,
              int isolationLevel,
              int colRefItem,
              double optimizerEstimatedRowCount,
              double optimizerEstimatedCost)
        throws StandardException

Construct a ScanResultSet.

Parameters:

activation - the activation

resultSetNumber - number of the result set (unique within statement)

resultRowTemplate - identifier of saved object for row template

lockMode - lock mode (record or table)

tableLocked - true if marked as table locked in SYS.SYSTABLES

isolationLevel - language isolation level for the result set

colRefItem - Identifier of saved object for accessedCols, -1 if need to fetch all columns.

optimizerEstimatedRowCount - estimated row count

optimizerEstimatedCost - estimated cost

Throws:

StandardException

Method Detail

initIsolationLevel

void initIsolationLevel()

Initialize the isolation level and the lock mode. If the result set was constructed with an explicit isolation level, or if the isolation level has already been initialized, this is a no-op. All sub-classes should invoke this method from their openCore() methods.

getLockMode

private int getLockMode(int languageLevel)

Get the lock mode based on the language isolation level. Always do row locking unless the isolation level is serializable or the table is marked as table locked.

Parameters:

languageLevel - the (language) isolation level

Returns:

lock mode

translateLanguageIsolationLevel

private int translateLanguageIsolationLevel(int languageLevel)

Translate isolation level from language to store.

Parameters:

languageLevel - language isolation level

Returns:

store isolation level

canGetInstantaneousLocks

abstract boolean canGetInstantaneousLocks()

Can we get instantaneous locks when getting share row locks at READ COMMITTED.

getScanIsolationLevel

public int getScanIsolationLevel()

Return the isolation level of the scan in the result set.

Specified by:

getScanIsolationLevel in interface NoPutResultSet

Overrides:

getScanIsolationLevel in class BasicNoPutResultSetImpl

Returns:

The isolation level of the scan (in TransactionController constants).

See Also:

NoPutResultSet.getScanIsolationLevel()

close

public void close()
           throws StandardException

Close the result set.

Specified by:

close in interface ResultSet

Overrides:

close in class NoPutResultSetImpl

Throws:

StandardException - if an error occurs