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Class sqlj.runtime.ExecutionContext

java.lang.Object
   |
   +----sqlj.runtime.ExecutionContext

public class ExecutionContext
extends Object
An execution context provides the context in which executable sql operations are preformed. An execution context object contains a number of operations for execution control, execution status, and execution cancellation. Execution control operations modify the semantics of subsequent sql operations executed on this context. Execution status operations describe the results of the last sql operation executed on this context. Execution cancellation methods terminate the currently executing sql operation on this context.

Note that concurrently executing sql operations are expected to use distinct execution contexts. The execution context implementation is not expected to support multiple sql operations executing using the same execution context object. The client is responsible for insuring the proper creation of distinct execution context instance where needed, or synchronizing the execution of operations on a particular execution context. It is also assumed that generated calls to methods on this class appear within a schronized block to avoid concurrent calls. Re-entrant SQL execution calls on the same connection context instance are supported.

See Also:
getExecutionContext

Variable Index

 o EXCEPTION_COUNT
Constant returned by getUpdateCount indicating that an exeception was thrown before the last execution was successfully completed, or no operation has yet been attempted on this context.
 o QUERY_COUNT
Constant returned by getUpdateCount indicating that the last execution produced a result set or iterator.

Constructor Index

 o ExecutionContext()

Method Index

 o cancel()
The cancel method can be used by one thread to cancel a sql operation that is currently being executed by another thread using this context.
 o execute()
Performs a generic execute on the currently registered statement.
 o executeQuery()
Performs an execute query on the currently registered statement.
 o executeUpdate()
Performs an execute update on the currently registered statement.
 o getMaxFieldSize()
The max field size limit (in bytes) is the maximum amount of data returned for any column value for sql operations subsequently executed using this context; it only applies to BINARY, VARBINARY, LONGVARBINARY, CHAR, VARCHAR, and LONGVARCHAR columns.
 o getMaxRows()
The max rows limit is the maximum number of rows that any ResultSetIterator or jdbc ResultSet returned by sql operations subsequently executed using this context can contain.
 o getNextResultSet()
Moves to the currently registered statement's next result.
 o getQueryTimeout()
The query timeout limit is the maxiumum number of seconds sql opeations subsequently executed using this context may take to complete.
 o getUpdateCount()
Returns the number of rows updated by the last sql operation to complete execution using this context.
 o getWarnings()
Returns the first warning reported by the last sql operation to complete execution using this context.
 o registerStatement(ConnectionContext, Object, int)
Creates, registers and returns a statement.
 o releaseStatement()
Releases the currently registered statement, signaling that all execution-related operations have completed.
 o setMaxFieldSize(int)
The max field size limit (in bytes) is the maximum amount of data returned for any column value for sql operations subsequently executed using this context; it only applies to BINARY, VARBINARY, LONGVARBINARY, CHAR, VARCHAR, and LONGVARCHAR columns.
 o setMaxRows(int)
The max rows limit is the maximum number of rows that any ResultSetIterator or jdbc ResultSet returned by sql operations subsequently executed using this context can contain.
 o setQueryTimeout(int)
The query timeout limit is the maxiumum number of seconds sql opeations subsequently executed using this context may take to complete.

Variables

 o QUERY_COUNT
 public static final int QUERY_COUNT
Constant returned by getUpdateCount indicating that the last execution produced a result set or iterator.

See Also:
getUpdateCount
 o EXCEPTION_COUNT
 public static final int EXCEPTION_COUNT
Constant returned by getUpdateCount indicating that an exeception was thrown before the last execution was successfully completed, or no operation has yet been attempted on this context.

See Also:
getUpdateCount

Constructors

 o ExecutionContext
 public ExecutionContext()

Methods

 o getMaxFieldSize
 public synchronized int getMaxFieldSize()
The max field size limit (in bytes) is the maximum amount of data returned for any column value for sql operations subsequently executed using this context; it only applies to BINARY, VARBINARY, LONGVARBINARY, CHAR, VARCHAR, and LONGVARCHAR columns. These columns may be fetched into Java targets of type byte[], String, or stream. The limit effects both out and in-out parameters passed, and the result returned from any executable sql operation. If the limit is exceeded, the excess data is silently discarded.

By default, the max field size limit is zero (unlimited)

Returns:
the current max field size limit; zero means unlimited
 o setMaxFieldSize
 public synchronized void setMaxFieldSize(int max)
The max field size limit (in bytes) is the maximum amount of data returned for any column value for sql operations subsequently executed using this context; it only applies to BINARY, VARBINARY, LONGVARBINARY, CHAR, VARCHAR, and LONGVARCHAR columns. These columns may be fetched into Java targets of type byte[], String, or stream. The limit effects both out and in-out parameters passed, and the result returned from any executable sql operation. If the limit is exceeded, the excess data is silently discarded. For maximum portability use values greater than 256.

By default, the max field size limit is zero (unlimited)

Note: max field size is an optional feature that may not be supported by some implementations. Setting max field size to a non-default value may cause an SQLException to be raised when an SQL operation is executed using this context.

Parameters:
max - the new max field size limit; zero means unlimited
 o getMaxRows
 public synchronized int getMaxRows()
The max rows limit is the maximum number of rows that any ResultSetIterator or jdbc ResultSet returned by sql operations subsequently executed using this context can contain. If the limit is exceeded, the excess rows are silently dropped.

By default, the max rows limit is zero (unlimited)

Returns:
the current max rows limit; zero means unlimited
 o setMaxRows
 public synchronized void setMaxRows(int max)
The max rows limit is the maximum number of rows that any ResultSetIterator or jdbc ResultSet returned by sql operations subsequently executed using this context can contain. If the limit is exceeded, the excess rows are silently dropped.

By default, the max rows limit is zero (unlimited)

Note: max rows is an optional feature that may not be supported by some implementations. Setting max rows to a non-default value may cause an SQLException to be raised when an SQL operation is executed using this context.

Parameters:
max - the new max rows limit; zero means unlimited
 o getQueryTimeout
 public synchronized int getQueryTimeout()
The query timeout limit is the maxiumum number of seconds sql opeations subsequently executed using this context may take to complete. If execution of the sql operation exceeds the limit, a SQLException is thrown.

By default, the query timeout limit is zero (unlimited)

Returns:
the current query timeout limit in seconds; zero means unlimited
 o setQueryTimeout
 public synchronized void setQueryTimeout(int seconds)
The query timeout limit is the maxiumum number of seconds sql opeations subsequently executed using this context may take to complete. If execution of the sql operation exceeds the limit, a SQLException is thrown.

By default, the query timeout limit is zero (unlimited)

Note: query timeout is an optional feature that may not be supported by some implementations. Setting query timeout to a non-default value may cause an SQLException to be raised when an SQL operation is executed using this context.

Parameters:
seconds - the new query timeout limit in seconds; zero means unlimited
 o getWarnings
 public synchronized SQLWarning getWarnings()
Returns the first warning reported by the last sql operation to complete execution using this context. Subsequent warnings resultant from the same operation will be chained to this SQLWarning. The SQLWarning chain returned represents those warnings which occured during the execution of the last sql operation and the subsequent binding of any output host variables.

Note: If you are processing an iterator, then any warnings associated with iterator column reads will be chained on the iterator object.

Returns:
the first SQLWarning or null if no warnings occurred
 o getUpdateCount
 public synchronized int getUpdateCount()
Returns the number of rows updated by the last sql operation to complete execution using this context. 0 is returned if the last sql operation was not a DML statement. QUERY_COUNT is returned if the last sql operation produced an iterator or result set. EXCEPTION_COUNT is returned if an exception occurred before the last sql operation completed execution, or no operation has yet been completed.

Returns:
the number of rows updated by the last operation
 o cancel
 public void cancel() throws SQLException
The cancel method can be used by one thread to cancel a sql operation that is currently being executed by another thread using this context. Note that this method has no effect if there is no statement currently being executed for this execution context.

Throws: SQLException
if unable to cancel
See Also:
executeUpdate, executeQuery
 o registerStatement
 public RTStatement registerStatement(ConnectionContext connCtx,
                                      Object profileKey,
                                      int stmtNdx) throws SQLException
Creates, registers and returns a statement. This method is called by generated code. Most programmers will not need to call it directly.

The statement is created by accessing the connected profile within connection context "connCtx" that has the key "profileKey". The statement at index "stmtNdx" in the connected profile is created using the getStatement method.

The statement created is registered and becomes the current statement of this execution context.

For each of the max rows, max field size, and query timeout attributes of this execution context, if the attribute has a non-default value, then the corresponding attribute of the registered statement is set to this value. An exception is raised if the statement does not support setting the attribute. The attributes of the execution context contained by the passed connection context are not used by this method. Note that if this method throws an exception, no statement will be registered.

Note: It is assumed that this method is called within a block that is synchronized on this execution context instance. Subsequent calls to execute and release the statement returned should also appear within the same synchronized block. If there is another statement currently registered on this execution context, it is assumed that this method is a recursive callin initiated by the currently registered statement. In such cases, state involving the currently registered statement is saved, and the statement returned by this method becomes the currently registered statement. Once this new statement completes execution and is released, the previous statement is restored as the currently registered statement.

Parameters:
connCtx - the connection context that contains the profile that contains the statement to register.
profileKey - the key of the connected profile within the connection context.
stmtNdx - the 0-based index of the statement within the profile to be registered.
Throws: SQLException
if the max fields size, max rows, or query timeout cannot be set on the registered statement.
See Also:
releaseStatement, getStatement, getConnectedProfile
 o executeUpdate
 public int executeUpdate() throws SQLException
Performs an execute update on the currently registered statement. When the statement is released, the update count is updated accordingly.

This method is called by generated code. Most programmers will not need to call it directly.

Note: It is assumed that this method is called within a block that is synchronized on this execution context instance. Furthermore, it is also assumed that the previous call to register and the subsequent call to release the current statement also appear within the same synchronized block.

Returns:
the result of calling executeUpdate on the currently registered statement
Throws: SQLException
if an error occurs during the execution of the currently registered statement.
See Also:
executeUpdate, registerStatement
 o executeQuery
 public RTResultSet executeQuery() throws SQLException
Performs an execute query on the currently registered statement. When the statement is released, the update count is set to QUERY_COUNT.

This method is called by generated code. Most programmers will not need to call it directly.

Note: It is assumed that this method is called within a block that is synchronized on this execution context instance. Furthermore, it is also assumed that the previous call to register and the subsequent call to release the current statement also appear within the same synchronized block.

Returns:
the result of calling executeRTQuery on the currently registered statement
Throws: SQLException
if an error occurs during the execution of the currently registered statement.
See Also:
executeRTQuery, registerStatement
 o execute
 public boolean execute() throws SQLException
Performs a generic execute on the currently registered statement. Under some situations a single SQL CALL statement may return multiple result sets. The "execute" and "getNextResultSet" methods allow navigation through multiple results.

The "execute" method executes the currently registered statement and returns true if it produced a side-channel result set, false otherwise. The getNextResultSet method is used to obtain the result set. When the statement is released, the update count will be set to QUERY_COUNT.

Notes:

Returns:
true if the statement produced a side-channel result set, false otherwise.
Throws: SQLException
if an error occurs during the execution of the currently registered statement.
See Also:
execute, registerStatement, getNextResultSet
 o getNextResultSet
 public synchronized ResultSet getNextResultSet() throws SQLException
Moves to the currently registered statement's next result. The first time this method is called after a SQL operation is executed, the first side-channel result set is returned (if any). Further calls to getNextResultSet will move to any subsequent results. getNextResultSet implicitly closes any open result set previously obtained with getNextResultSet.

getNextResultSet returns null when there are no further results. null is also returned if the last SQL operation executed did not produce side-channel results, or an SQL operation has not yet been executed on this execution context.

Notes:

Returns:
the next side-channel result set, or null if there are no further results.
Throws: SQLException
if an error occurs obtaining the next result set.
See Also:
getResultSet, getMoreResults, execute, registerStatement
 o releaseStatement
 public void releaseStatement() throws SQLException
Releases the currently registered statement, signaling that all execution-related operations have completed. After this method has been returned from, it is safe to call registerStatement again. The SQL warnings and updated count are updated as reflected by the registered statement and the execution results.

This method calls the executeComplete method of the registered statement.

If the execution of the currently registered statement produced multiple results and not all results have been processed, then this operation is a no-op. In such cases, this method will be automatically called to release the statement once all results have been processed and getNextResultSet returns null.

This method is called by generated code. Most programmers will not need to call it directly.

Note: It is assumed that this method is called within a block that is synchronized on this execution context instance. Furthermore, it is also assumed that the previous calls to register and execute the current statement also appeared within the same synchronized block.

Throws: SQLException
if an error occurs retrieving the warnings
See Also:
registerStatement, executeComplete

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