Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.diag.TransactionTable

public Class TransactionTable

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

 select * from SYSCS_DIAG.TRANSACTION_TABLE

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

The TransactionTable virtual table has the following columns:

XID varchar(15) - not nullable. The transaction id, this can be joined with the LockTable virtual table's XID.
GLOBAL_XID varchar(140) - nullable. The global transaction id, only set if this transaction is a participant in a distributed transaction.
USERNAME varchar(128) - nullable. The user name, or APP by default. May appear null if the transaction is started by Derby.
TYPE varchar(30) - not nullable. UserTransaction or an internal transaction spawned by Derby.
STATUS varchar(8) - not nullable. IDLE or ACTIVE. A transaction is IDLE only when it is first created or right after it commits. Any transaction that holds or has held any resource in the database is ACTIVE. Accessing the TransactionTable virtual table without using the class alias will not activate the transaction.
FIRST_INSTANT varchar(20) - nullable. If null, this is a read only transaction. If not null, this is the first log record instant written by the transaction.
SQL_TEXT VARCHAR(32672) - nullable. if null, this transaction is currently not being executed in the database. If not null, this is the SQL statement currently being executed in the database.

Modifier and Type	Field and Description
private static final ResultColumnDescriptor[]	columnInfo
pack-priv int	currentRow
pack-priv boolean	initialized
private static final ResultSetMetaData	metadata
private TransactionInfo[]	transactionTable
private boolean	wasNull

Modifier and Type

Field and Description

private static final ResultColumnDescriptor[]

columnInfo

pack-priv int

currentRow

pack-priv boolean

initialized

private static final ResultSetMetaData

metadata

private TransactionInfo[]

transactionTable

private boolean

wasNull

Constructor Summary

Access	Constructor and Description
public	TransactionTable()

Method Summary

Modifier and Type	Method and Description
public void	close() Implements java.sql.ResultSet.close. Releases this `ResultSet` object's database and JDBC resources immediately instead of waiting for this to happen when it is automatically closed.
public double	getEstimatedCostPerInstantiation(VTIEnvironment The state variable for optimizing the Table Function. vtiEnvironment) Implements org.apache.derby.vti.VTICosting.getEstimatedCostPerInstantiation. Get the estimated cost for a single instantiation of a Table Function.
public double	getEstimatedRowCount(VTIEnvironment The state variable for optimizing the Table Function. vtiEnvironment) Implements org.apache.derby.vti.VTICosting.getEstimatedRowCount. Get the estimated row count for a single scan of a Table Function.
public ResultSetMetaData	getMetaData() Overrides org.apache.derby.vti.VTITemplate.getMetaData. Implements java.sql.ResultSet.getMetaData. Retrieves the number, types and properties of this `ResultSet` object's columns.
public String	getString(int the first column is 1, the second is 2, ... columnNumber) Overrides org.apache.derby.vti.VTITemplate.getString. Implements java.sql.ResultSet.getString. All columns in TransactionTable VTI is of String type.
public boolean	next() Implements java.sql.ResultSet.next. Moves the cursor forward one row from its current position.
public boolean	Returns: false supportsMultipleInstantiations(VTIEnvironment The state variable for optimizing the Table Function. vtiEnvironment) Implements org.apache.derby.vti.VTICosting.supportsMultipleInstantiations. Find out if the ResultSet of the Table Function can be instantiated multiple times.
public boolean	wasNull() Overrides org.apache.derby.vti.VTITemplate.wasNull. Implements java.sql.ResultSet.wasNull. Reports whether the last column read had a value of SQL `NULL`.

Modifier and Type

Method and Description

public void

close()

Implements java.sql.ResultSet.close.

Releases this ResultSet object's database and JDBC resources immediately instead of waiting for this to happen when it is automatically closed.

public double

getEstimatedCostPerInstantiation(VTIEnvironment

The state variable for optimizing the Table Function.

vtiEnvironment)

Implements org.apache.derby.vti.VTICosting.getEstimatedCostPerInstantiation.

Get the estimated cost for a single instantiation of a Table Function.

public double

getEstimatedRowCount(VTIEnvironment

The state variable for optimizing the Table Function.

vtiEnvironment)

Implements org.apache.derby.vti.VTICosting.getEstimatedRowCount.

Get the estimated row count for a single scan of a Table Function.

public ResultSetMetaData

getMetaData()

Overrides org.apache.derby.vti.VTITemplate.getMetaData.

Implements java.sql.ResultSet.getMetaData.

Retrieves the number, types and properties of this ResultSet object's columns.

public String

getString(int

the first column is 1, the second is 2, ...

columnNumber)

Overrides org.apache.derby.vti.VTITemplate.getString.

Implements java.sql.ResultSet.getString.

All columns in TransactionTable VTI is of String type.

public boolean

next()

Implements java.sql.ResultSet.next.

Moves the cursor forward one row from its current position.

public boolean

Returns:

false

supportsMultipleInstantiations(VTIEnvironment

The state variable for optimizing the Table Function.

vtiEnvironment)

Implements org.apache.derby.vti.VTICosting.supportsMultipleInstantiations.

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

public boolean

wasNull()

Overrides org.apache.derby.vti.VTITemplate.wasNull.

Implements java.sql.ResultSet.wasNull.

Reports whether the last column read had a value of SQL NULL.

Field Detail

columnInfo	back to summary
private static final ResultColumnDescriptor[] columnInfo

currentRow	back to summary
pack-priv int currentRow

initialized	back to summary
pack-priv boolean initialized

metadata	back to summary
private static final ResultSetMetaData metadata

transactionTable	back to summary
private TransactionInfo[] transactionTable

wasNull	back to summary
private boolean wasNull

Constructor Detail

TransactionTable	back to summary
public TransactionTable() throws StandardException

Method Detail

close back to summary

close	back to summary
public void close() Implements java.sql.ResultSet.close. Doc from java.sql.ResultSet.close. Releases this `ResultSet` object's database and JDBC resources immediately instead of waiting for this to happen when it is automatically closed. The closing of a `ResultSet` object does not close the `Blob`, `Clob` or `NClob` objects created by the `ResultSet`. `Blob`, `Clob` or `NClob` objects remain valid for at least the duration of the transaction in which they are created, unless their `free` method is invoked. When a `ResultSet` is closed, any `ResultSetMetaData` instances that were created by calling the `getMetaData` method remain accessible. Note A `ResultSet` object is automatically closed by the `Statement` object that generated it when that `Statement` object is closed, re-executed, or is used to retrieve the next result from a sequence of multiple results. Calling the method `close` on a `ResultSet` object that is already closed is a no-op. See Also `java.sql.ResultSet#close`

public void close()

Implements java.sql.ResultSet.close.

Doc from java.sql.ResultSet.close.

Releases this ResultSet object's database and JDBC resources immediately instead of waiting for this to happen when it is automatically closed.

The closing of a ResultSet object does not close the Blob, Clob or NClob objects created by the ResultSet. Blob, Clob or NClob objects remain valid for at least the duration of the transaction in which they are created, unless their free method is invoked.

When a ResultSet is closed, any ResultSetMetaData instances that were created by calling the getMetaData method remain accessible.

Note

A ResultSet object is automatically closed by the Statement object that generated it when that Statement object is closed, re-executed, or is used to retrieve the next result from a sequence of multiple results.

Calling the method close on a ResultSet object that is already closed is a no-op.

See Also: java.sql.ResultSet#close

getEstimatedCostPerInstantiation back to summary

getEstimatedCostPerInstantiation	back to summary
public double getEstimatedCostPerInstantiation(VTIEnvironment vtiEnvironment) Implements org.apache.derby.vti.VTICosting.getEstimatedCostPerInstantiation. Doc from org.apache.derby.vti.VTICosting.getEstimatedCostPerInstantiation. Get the estimated cost for a single instantiation of a Table Function. Parameters vtiEnvironment:VTIEnvironment The state variable for optimizing the Table Function. Returns:double The estimated cost for a single instantiation of the Table Function. See Also `VTICosting#getEstimatedCostPerInstantiation`

public double getEstimatedCostPerInstantiation(VTIEnvironment vtiEnvironment)

Implements org.apache.derby.vti.VTICosting.getEstimatedCostPerInstantiation.

Doc from org.apache.derby.vti.VTICosting.getEstimatedCostPerInstantiation.

Get the estimated cost for a single instantiation of a Table Function.

Parameters

vtiEnvironment:VTIEnvironment: The state variable for optimizing the Table Function.

Returns:double

The estimated cost for a single instantiation of the Table Function.

getEstimatedRowCount back to summary

getEstimatedRowCount	back to summary
public double getEstimatedRowCount(VTIEnvironment vtiEnvironment) Implements org.apache.derby.vti.VTICosting.getEstimatedRowCount. Doc from org.apache.derby.vti.VTICosting.getEstimatedRowCount. Get the estimated row count for a single scan of a Table Function. Parameters vtiEnvironment:VTIEnvironment The state variable for optimizing the Table Function. Returns:double The estimated row count for a single scan of the Table Function. See Also `VTICosting#getEstimatedRowCount`

public double getEstimatedRowCount(VTIEnvironment vtiEnvironment)

Implements org.apache.derby.vti.VTICosting.getEstimatedRowCount.

Doc from org.apache.derby.vti.VTICosting.getEstimatedRowCount.

Get the estimated row count for a single scan of a Table Function.

Parameters

vtiEnvironment:VTIEnvironment: The state variable for optimizing the Table Function.

Returns:double

The estimated row count for a single scan of the Table Function.

See Also

VTICosting#getEstimatedRowCount

getMetaData back to summary

public ResultSetMetaData getMetaData()

Overrides org.apache.derby.vti.VTITemplate.getMetaData.

Implements java.sql.ResultSet.getMetaData.

Doc from java.sql.ResultSet.getMetaData.

Retrieves the number, types and properties of this ResultSet object's columns.

Returns:ResultSetMetaData: the description of this ResultSet object's columns
See Also: java.sql.ResultSet#getMetaData

getString back to summary

getString	back to summary
public String getString(int columnNumber) Overrides org.apache.derby.vti.VTITemplate.getString. Implements java.sql.ResultSet.getString. All columns in TransactionTable VTI is of String type. Parameters columnNumber:int Doc from java.sql.ResultSet.getString. the first column is 1, the second is 2, ... Returns:String Doc from java.sql.ResultSet.getString. the column value; if the value is SQL `NULL`, the value returned is `null` See Also `java.sql.ResultSet#getString`

public String getString(int columnNumber)

Overrides org.apache.derby.vti.VTITemplate.getString.

Implements java.sql.ResultSet.getString.

All columns in TransactionTable VTI is of String type.

Parameters

columnNumber:int

Doc from java.sql.ResultSet.getString.

the first column is 1, the second is 2, ...

Returns:String

Doc from java.sql.ResultSet.getString.

the column value; if the value is SQL NULL, the value returned is null

See Also

java.sql.ResultSet#getString

next back to summary

next	back to summary
public boolean next() throws SQLException Implements java.sql.ResultSet.next. Doc from java.sql.ResultSet.next. Moves the cursor forward one row from its current position. A `ResultSet` cursor is initially positioned before the first row; the first call to the method `next` makes the first row the current row; the second call makes the second row the current row, and so on. When a call to the `next` method returns `false`, the cursor is positioned after the last row. Any invocation of a `ResultSet` method which requires a current row will result in a `SQLException` being thrown. If the result set type is `TYPE_FORWARD_ONLY`, it is vendor specified whether their JDBC driver implementation will return `false` or throw an `SQLException` on a subsequent call to `next`. If an input stream is open for the current row, a call to the method `next` will implicitly close it. A `ResultSet` object's warning chain is cleared when a new row is read. Returns:boolean `true` if the new current row is valid; `false` if there are no more rows Exceptions SQLException: if no transaction context can be found See Also `java.sql.ResultSet#next`

public boolean next() throws SQLException

Implements java.sql.ResultSet.next.

Doc from java.sql.ResultSet.next.

Moves the cursor forward one row from its current position. A ResultSet cursor is initially positioned before the first row; the first call to the method next makes the first row the current row; the second call makes the second row the current row, and so on.

When a call to the next method returns false, the cursor is positioned after the last row. Any invocation of a ResultSet method which requires a current row will result in a SQLException being thrown. If the result set type is TYPE_FORWARD_ONLY, it is vendor specified whether their JDBC driver implementation will return false or throw an SQLException on a subsequent call to next.

If an input stream is open for the current row, a call to the method next will implicitly close it. A ResultSet object's warning chain is cleared when a new row is read.

Returns:boolean

true if the new current row is valid; false if there are no more rows

Exceptions

SQLException:: if no transaction context can be found

See Also

java.sql.ResultSet#next

supportsMultipleInstantiations back to summary

supportsMultipleInstantiations	back to summary
public boolean supportsMultipleInstantiations(VTIEnvironment vtiEnvironment) Implements org.apache.derby.vti.VTICosting.supportsMultipleInstantiations. Doc from org.apache.derby.vti.VTICosting.supportsMultipleInstantiations. Find out if the ResultSet of the Table Function can be instantiated multiple times. Parameters vtiEnvironment:VTIEnvironment The state variable for optimizing the Table Function. Returns:boolean false See Also `VTICosting#supportsMultipleInstantiations`

public boolean supportsMultipleInstantiations(VTIEnvironment vtiEnvironment)

Implements org.apache.derby.vti.VTICosting.supportsMultipleInstantiations.

Doc from org.apache.derby.vti.VTICosting.supportsMultipleInstantiations.

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

Parameters

vtiEnvironment:VTIEnvironment: The state variable for optimizing the Table Function.

Returns:boolean

false

wasNull back to summary

wasNull	back to summary
public boolean wasNull() Overrides org.apache.derby.vti.VTITemplate.wasNull. Implements java.sql.ResultSet.wasNull. Doc from java.sql.ResultSet.wasNull. Reports whether the last column read had a value of SQL `NULL`. Note that you must first call one of the getter methods on a column to try to read its value and then call the method `wasNull` to see if the value read was SQL `NULL`. Returns:boolean `true` if the last column value read was SQL `NULL` and `false` otherwise See Also `java.sql.ResultSet#wasNull`

public boolean wasNull()

Overrides org.apache.derby.vti.VTITemplate.wasNull.

Implements java.sql.ResultSet.wasNull.

Doc from java.sql.ResultSet.wasNull.

Reports whether the last column read had a value of SQL NULL. Note that you must first call one of the getter methods on a column to try to read its value and then call the method wasNull to see if the value read was SQL NULL.

Returns:boolean: true if the last column value read was SQL NULL and false otherwise
See Also: java.sql.ResultSet#wasNull

public Class TransactionTable

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail