org.h2.command

Class Command

java.lang.Object

org.h2.command.Command

All Implemented Interfaces:

CommandInterface

Direct Known Subclasses:

CommandContainer

public abstract class Command
extends java.lang.Object
implements CommandInterface

Represents a SQL statement. This object is only used on the server side.

Field Summary

Fields

Modifier and Type	Field and Description
protected Session	session The session.
protected long	startTimeNanos The last start time.

Fields inherited from interface org.h2.command.CommandInterface

ALTER_INDEX_RENAME, ALTER_SCHEMA_RENAME, ALTER_SEQUENCE, ALTER_TABLE_ADD_COLUMN, ALTER_TABLE_ADD_CONSTRAINT_CHECK, ALTER_TABLE_ADD_CONSTRAINT_PRIMARY_KEY, ALTER_TABLE_ADD_CONSTRAINT_REFERENTIAL, ALTER_TABLE_ADD_CONSTRAINT_UNIQUE, ALTER_TABLE_ALTER_COLUMN_CHANGE_TYPE, ALTER_TABLE_ALTER_COLUMN_DEFAULT, ALTER_TABLE_ALTER_COLUMN_NOT_NULL, ALTER_TABLE_ALTER_COLUMN_NULL, ALTER_TABLE_ALTER_COLUMN_RENAME, ALTER_TABLE_ALTER_COLUMN_SELECTIVITY, ALTER_TABLE_DROP_COLUMN, ALTER_TABLE_DROP_CONSTRAINT, ALTER_TABLE_RENAME, ALTER_TABLE_RENAME_CONSTRAINT, ALTER_TABLE_SET_REFERENTIAL_INTEGRITY, ALTER_USER_ADMIN, ALTER_USER_RENAME, ALTER_USER_SET_PASSWORD, ALTER_VIEW, ANALYZE, BACKUP, BEGIN, CALL, CHECKPOINT, CHECKPOINT_SYNC, COMMENT, COMMIT, COMMIT_TRANSACTION, CREATE_AGGREGATE, CREATE_ALIAS, CREATE_CONSTANT, CREATE_DOMAIN, CREATE_INDEX, CREATE_LINKED_TABLE, CREATE_ROLE, CREATE_SCHEMA, CREATE_SEQUENCE, CREATE_TABLE, CREATE_TRIGGER, CREATE_USER, CREATE_VIEW, DEALLOCATE, DELETE, DROP_AGGREGATE, DROP_ALIAS, DROP_ALL_OBJECTS, DROP_CONSTANT, DROP_DOMAIN, DROP_INDEX, DROP_ROLE, DROP_SCHEMA, DROP_SEQUENCE, DROP_TABLE, DROP_TRIGGER, DROP_USER, DROP_VIEW, EXECUTE, EXPLAIN, EXPLAIN_ANALYZE, GRANT, INSERT, MERGE, NO_OPERATION, PREPARE, PREPARE_COMMIT, REPLACE, REVOKE, ROLLBACK, ROLLBACK_TO_SAVEPOINT, ROLLBACK_TRANSACTION, RUNSCRIPT, SAVEPOINT, SCRIPT, SELECT, SET, SET_AUTOCOMMIT_FALSE, SET_AUTOCOMMIT_TRUE, SHUTDOWN, SHUTDOWN_COMPACT, SHUTDOWN_DEFRAG, SHUTDOWN_IMMEDIATELY, TRUNCATE_TABLE, UNKNOWN, UPDATE

Method Summary

Methods

Modifier and Type	Method and Description
void	cancel() Cancel the statement if it is still processing.
boolean	canReuse() Whether the command is already closed (in which case it can be re-used).
protected void	checkCanceled() Check if this command has been canceled, and throw an exception if yes.
void	close() Close the statement.
ResultInterface	executeQuery(int maxrows, boolean scrollable) Execute a query and return the result.
int	executeUpdate() Execute the statement
ResultInterface	getMetaData() Get an empty result set containing the meta data of the result.
abstract java.util.ArrayList<? extends ParameterInterface>	getParameters() Get the list of parameters.
boolean	isCacheable()
abstract boolean	isQuery() Check if this command is a query.
abstract boolean	isReadOnly() Check if this command is read only.
abstract boolean	isTransactional() Check if this command is transactional.
abstract void	prepareJoinBatch() Prepare join batching.
ResultInterface	query(int maxrows) Execute a query statement, if this is possible.
abstract ResultInterface	queryMeta() Get an empty result set containing the meta data.
void	reuse() The command is now re-used, therefore reset the canReuse flag, and the parameter values.
java.lang.String	toString()
int	update() Execute an updating statement (for example insert, delete, or update), if this is possible.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.h2.command.CommandInterface

getCommandType

Field Detail

session

protected final Session session

The session.

startTimeNanos

protected long startTimeNanos

The last start time.

Method Detail

isTransactional

public abstract boolean isTransactional()

Check if this command is transactional. If it is not, then it forces the current transaction to commit.

Returns:

true if it is

isQuery

public abstract boolean isQuery()

Check if this command is a query.

Specified by:

isQuery in interface CommandInterface

Returns:

true if it is

prepareJoinBatch

public abstract void prepareJoinBatch()

Prepare join batching.

getParameters

public abstract java.util.ArrayList<? extends ParameterInterface> getParameters()

Get the list of parameters.

Specified by:

getParameters in interface CommandInterface

Returns:

the list of parameters

isReadOnly

public abstract boolean isReadOnly()

Check if this command is read only.

Returns:

true if it is

queryMeta

public abstract ResultInterface queryMeta()

Get an empty result set containing the meta data.

Returns:

an empty result set

update

public int update()

Execute an updating statement (for example insert, delete, or update), if this is possible.

Returns:

the update count

Throws:

DbException - if the command is not an updating statement

query

public ResultInterface query(int maxrows)

Execute a query statement, if this is possible.

Parameters:

maxrows - the maximum number of rows returned

Returns:

the local result set

Throws:

DbException - if the command is not a query

getMetaData

public final ResultInterface getMetaData()

Description copied from interface: CommandInterface

Get an empty result set containing the meta data of the result.

Specified by:

getMetaData in interface CommandInterface

Returns:

the empty result

checkCanceled

protected void checkCanceled()

Check if this command has been canceled, and throw an exception if yes.

Throws:

DbException - if the statement has been canceled

executeQuery

public ResultInterface executeQuery(int maxrows,
                           boolean scrollable)

Execute a query and return the result. This method prepares everything and calls query(int) finally.

Specified by:

executeQuery in interface CommandInterface

Parameters:

maxrows - the maximum number of rows to return

scrollable - if the result set must be scrollable (ignored)

Returns:

the result set

executeUpdate

public int executeUpdate()

Description copied from interface: CommandInterface

Execute the statement

Specified by:

executeUpdate in interface CommandInterface

Returns:

the update count

close

public void close()

Description copied from interface: CommandInterface

Close the statement.

Specified by:

close in interface CommandInterface

cancel

public void cancel()

Description copied from interface: CommandInterface

Cancel the statement if it is still processing.

Specified by:

cancel in interface CommandInterface

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

isCacheable

public boolean isCacheable()

canReuse

public boolean canReuse()

Whether the command is already closed (in which case it can be re-used).

Returns:

true if it can be re-used

reuse

public void reuse()

The command is now re-used, therefore reset the canReuse flag, and the parameter values.