LockTable

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org.apache.derby.diag
Class LockTable

java.lang.Object
  org.apache.derby.vti.VTITemplate
      org.apache.derby.diag.LockTable

All Implemented Interfaces:: java.sql.ResultSet, org.apache.derby.vti.VTICosting

public class LockTable
extends org.apache.derby.vti.VTITemplate
implements org.apache.derby.vti.VTICosting

LockTable is a virtual table that shows all locks currently held in the database. This virtual table can be invoked by calling it directly

 select * from new org.apache.derby.diag.LockTable() t;

or through the system alias LOCKTABLE

 select * from new LOCKTABLE() t;

The LockTable virtual table takes a snap shot of the lock table while the system is in flux, so it is possible that some locks may be in transition state while the snap shot is taken. We choose to do this rather then impose extranous timing restrictions so that the use of this tool will not alter the normal timing and flow of execution in the application.

The LockTable virtual table has the following columns:

XID varchar(15) - not nullable. The transaction id, this can be joined with the TransactionTable virtual table's XID.
TYPE varchar(5) - nullable. The type of lock, ROW, TABLE, or LATCH
MODE varchar(4) - not nullable. The mode of the lock, "S", "U", "X", "IS", "IX".

S is shared lock (N/A to Latch)
U is update lock (N/A to Latch)
X is exclusive lock
IS is intent shared lock (N/A to Latch or Row lock)
IX is intent exclusive lock (N/A to Latch or Row lock)

TABLENAME varchar(128) - not nullable. The name of the base table the lock is for
LOCKNAME varchar(20) - not nullable. The name of the lock
STATE varchar(5) - nullable. GRANT or WAIT
TABLETYPE varchar(9) - not nullable. 'T' for user table, 'S' for system table
LOCKCOUNT varchar(5) - not nullable. Internal lock count.
INDEXNAME varchar(128) - normally null. If non-null, a lock is held on the index, this can only happen if this is not a user transaction.

Field Summary

static int ALL
          return all locks and latches

private static org.apache.derby.iapi.sql.ResultColumnDescriptor[] columnInfo


private java.util.Hashtable currentRow


private int flag


private boolean initialized


static int LATCH
          return only latches

private org.apache.derby.iapi.sql.conn.LanguageConnectionFactory lcf


private java.util.Enumeration lockTable


private static java.sql.ResultSetMetaData metadata


private org.apache.derby.impl.services.locks.TableNameInfo tabInfo


static int TABLE_AND_ROWLOCK
          return only table and row locks

private org.apache.derby.iapi.store.access.TransactionController tc


private boolean wasNull


Fields inherited from interface org.apache.derby.vti.VTICosting

defaultEstimatedCost, defaultEstimatedRowCount

Fields inherited from interface java.sql.ResultSet

CLOSE_CURSORS_AT_COMMIT, CONCUR_READ_ONLY, CONCUR_UPDATABLE, FETCH_FORWARD, FETCH_REVERSE, FETCH_UNKNOWN, HOLD_CURSORS_OVER_COMMIT, TYPE_FORWARD_ONLY, TYPE_SCROLL_INSENSITIVE, TYPE_SCROLL_SENSITIVE

Constructor Summary

LockTable()
          The normal way of instantiating a LockTable, equivalent to LockTable(org.apache.derby.diag.LockTable->TABLE_AND_ROWLOCK).

LockTable(int flag)
          This call is intrusive and should only be used under the supervision of technical support.

Method Summary

void close()
          This method closes the result set and frees any associated resources.

private java.util.Hashtable dumpLock(org.apache.derby.iapi.services.locks.Latch lock)
          Convert the lock information into a hashtable.

double getEstimatedCostPerInstantiation(org.apache.derby.vti.VTIEnvironment vtiEnvironment)
          Get the estimated cost for a single instantiation of a VTI.

double getEstimatedRowCount(org.apache.derby.vti.VTIEnvironment vtiEnvironment)
          Get the estimated row count for a single scan of a VTI.

java.sql.ResultSetMetaData getMetaData()
          This method returns data about the columns returned as part of the result set as a ResultSetMetaData instance.

java.lang.String getString(int columnNumber)
          All columns in TransactionTable VTI are of String type.

boolean next()
          This method advances to the next row in the result set.

boolean supportsMultipleInstantiations(org.apache.derby.vti.VTIEnvironment vtiEnvironment)
          Find out if the ResultSet of the VTI can be instantiated multiple times.

boolean wasNull()
          This method tests whether the value of the last column that was fetched was actually a SQL NULL value.

Methods inherited from class org.apache.derby.vti.VTITemplate

absolute, afterLast, beforeFirst, cancelRowUpdates, clearWarnings, deleteRow, findColumn, first, getArray, getArray, getAsciiStream, getAsciiStream, getBigDecimal, getBigDecimal, getBigDecimal, getBigDecimal, getBinaryStream, getBinaryStream, getBlob, getBlob, getBoolean, getBoolean, getByte, getByte, getBytes, getBytes, getCharacterStream, getCharacterStream, getClob, getClob, getConcurrency, getCursorName, getDate, getDate, getDate, getDate, getDouble, getDouble, getFetchDirection, getFetchSize, getFloat, getFloat, getInt, getInt, getLong, getLong, getObject, getObject, getObject, getObject, getRef, getRef, getRow, getShort, getShort, getStatement, getString, getTime, getTime, getTime, getTime, getTimestamp, getTimestamp, getTimestamp, getTimestamp, getType, getUnicodeStream, getUnicodeStream, getURL, getURL, getWarnings, insertRow, isAfterLast, isBeforeFirst, isFirst, isLast, last, moveToCurrentRow, moveToInsertRow, previous, refreshRow, relative, rowDeleted, rowInserted, rowUpdated, setFetchDirection, setFetchSize, updateArray, updateArray, updateAsciiStream, updateAsciiStream, updateBigDecimal, updateBigDecimal, updateBinaryStream, updateBinaryStream, updateBlob, updateBlob, updateBoolean, updateBoolean, updateByte, updateByte, updateBytes, updateBytes, updateCharacterStream, updateCharacterStream, updateClob, updateClob, updateDate, updateDate, updateDouble, updateDouble, updateFloat, updateFloat, updateInt, updateInt, updateLong, updateLong, updateNull, updateNull, updateObject, updateObject, updateObject, updateObject, updateRef, updateRef, updateRow, updateShort, updateShort, updateString, updateString, updateTime, updateTime, updateTimestamp, updateTimestamp

Methods inherited from class java.lang.Object

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

Field Detail

LATCH

public static final int LATCH

return only latches

See Also:: Constant Field Values

TABLE_AND_ROWLOCK

public static final int TABLE_AND_ROWLOCK

return only table and row locks

See Also:: Constant Field Values

ALL

public static final int ALL

return all locks and latches

See Also:: Constant Field Values

tc

private org.apache.derby.iapi.store.access.TransactionController tc

lcf

private org.apache.derby.iapi.sql.conn.LanguageConnectionFactory lcf

currentRow

private java.util.Hashtable currentRow

lockTable

private java.util.Enumeration lockTable

wasNull

private boolean wasNull

initialized

private boolean initialized

flag

private final int flag

tabInfo

private org.apache.derby.impl.services.locks.TableNameInfo tabInfo

columnInfo

private static final org.apache.derby.iapi.sql.ResultColumnDescriptor[] columnInfo

metadata

private static final java.sql.ResultSetMetaData metadata

Constructor Detail

LockTable

public LockTable()

The normal way of instantiating a LockTable, equivalent to LockTable(org.apache.derby.diag.LockTable->TABLE_AND_ROWLOCK). Only shows row and table lock and not latches. Latches are generally held for very short duration and are not of interest to Cloudscape users. Only under abnormal circumstances will one be interested in looking at latches.

LockTable

public LockTable(int flag)

This call is intrusive and should only be used under the supervision of technical support. Create an instance of the lock table which has transient latches as well as locks.

Method Detail

getMetaData

public java.sql.ResultSetMetaData getMetaData()

Description copied from interface: java.sql.ResultSet

This method returns data about the columns returned as part of the result set as a ResultSetMetaData instance.

Specified by:: getMetaData in interface java.sql.ResultSet

public boolean next()
             throws java.sql.SQLException

Description copied from interface: java.sql.ResultSet

This method advances to the next row in the result set. Any streams open on the current row are closed automatically.

Specified by:: next in interface java.sql.ResultSet

close

public void close()

Description copied from interface: java.sql.ResultSet

This method closes the result set and frees any associated resources.

Specified by:: close in interface java.sql.ResultSet

getString

public java.lang.String getString(int columnNumber)

All columns in TransactionTable VTI are of String type.

Specified by:: getString in interface java.sql.ResultSet

wasNull

public boolean wasNull()

Description copied from interface: java.sql.ResultSet

This method tests whether the value of the last column that was fetched was actually a SQL NULL value.

Specified by:: wasNull in interface java.sql.ResultSet

getEstimatedRowCount

public double getEstimatedRowCount(org.apache.derby.vti.VTIEnvironment vtiEnvironment)

Description copied from interface: org.apache.derby.vti.VTICosting

Get the estimated row count for a single scan of a VTI.

Specified by:: getEstimatedRowCount in interface org.apache.derby.vti.VTICosting

getEstimatedCostPerInstantiation

public double getEstimatedCostPerInstantiation(org.apache.derby.vti.VTIEnvironment vtiEnvironment)

Description copied from interface: org.apache.derby.vti.VTICosting

Get the estimated cost for a single instantiation of a VTI.

Specified by:: getEstimatedCostPerInstantiation in interface org.apache.derby.vti.VTICosting

supportsMultipleInstantiations

public boolean supportsMultipleInstantiations(org.apache.derby.vti.VTIEnvironment vtiEnvironment)

Description copied from interface: org.apache.derby.vti.VTICosting

Find out if the ResultSet of the VTI can be instantiated multiple times.

Specified by:: supportsMultipleInstantiations in interface org.apache.derby.vti.VTICosting

dumpLock

private java.util.Hashtable dumpLock(org.apache.derby.iapi.services.locks.Latch lock)
                              throws org.apache.derby.iapi.error.StandardException

Convert the lock information into a hashtable.

Overview

Package

Class

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Deprecated

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Field Summary
`static int`	`ALL` return all locks and latches
`private static org.apache.derby.iapi.sql.ResultColumnDescriptor[]`	`columnInfo`
`private java.util.Hashtable`	`currentRow`
`private int`	`flag`
`private boolean`	`initialized`
`static int`	`LATCH` return only latches
`private org.apache.derby.iapi.sql.conn.LanguageConnectionFactory`	`lcf`
`private java.util.Enumeration`	`lockTable`
`private static java.sql.ResultSetMetaData`	`metadata`
`private org.apache.derby.impl.services.locks.TableNameInfo`	`tabInfo`
`static int`	`TABLE_AND_ROWLOCK` return only table and row locks
`private org.apache.derby.iapi.store.access.TransactionController`	`tc`
`private boolean`	`wasNull`

Constructor Summary
`LockTable()` The normal way of instantiating a LockTable, equivalent to LockTable(org.apache.derby.diag.LockTable->TABLE_AND_ROWLOCK).
`LockTable(int flag)` This call is intrusive and should only be used under the supervision of technical support.

Method Summary
`void`	`close()` This method closes the result set and frees any associated resources.
`private java.util.Hashtable`	`dumpLock(org.apache.derby.iapi.services.locks.Latch lock)` Convert the lock information into a hashtable.
`double`	`getEstimatedCostPerInstantiation(org.apache.derby.vti.VTIEnvironment vtiEnvironment)` Get the estimated cost for a single instantiation of a VTI.
`double`	`getEstimatedRowCount(org.apache.derby.vti.VTIEnvironment vtiEnvironment)` Get the estimated row count for a single scan of a VTI.
`java.sql.ResultSetMetaData`	`getMetaData()` This method returns data about the columns returned as part of the result set as a `ResultSetMetaData` instance.
`java.lang.String`	`getString(int columnNumber)` All columns in TransactionTable VTI are of String type.
`boolean`	`next()` This method advances to the next row in the result set.
`boolean`	`supportsMultipleInstantiations(org.apache.derby.vti.VTIEnvironment vtiEnvironment)` Find out if the ResultSet of the VTI can be instantiated multiple times.
`boolean`	`wasNull()` This method tests whether the value of the last column that was fetched was actually a SQL NULL value.

org.apache.derby.diag Class LockTable

LATCH

TABLE_AND_ROWLOCK

ALL

tc

lcf

currentRow

lockTable

wasNull

initialized

flag

tabInfo

columnInfo

metadata

LockTable

LockTable

getMetaData

next

close

getString

wasNull

getEstimatedRowCount

getEstimatedCostPerInstantiation

supportsMultipleInstantiations

dumpLock

org.apache.derby.diag
Class LockTable