Package org.h2.command

Class Command

java.lang.Object

org.h2.command.Command

All Implemented Interfaces:

java.lang.AutoCloseable, CommandInterface

Direct Known Subclasses:

CommandContainer, CommandList

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	Description
private boolean	cancel	If this query was canceled.
private boolean	canReuse
protected SessionLocal	session	The session.
private java.lang.String	sql
protected long	startTimeNanos	The last start time.
private Trace	trace	The trace module.

Fields inherited from interface org.h2.command.CommandInterface

ALTER_DOMAIN_ADD_CONSTRAINT, ALTER_DOMAIN_DEFAULT, ALTER_DOMAIN_DROP_CONSTRAINT, ALTER_DOMAIN_ON_UPDATE, ALTER_DOMAIN_RENAME, ALTER_DOMAIN_RENAME_CONSTRAINT, 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_DEFAULT_ON_NULL, ALTER_TABLE_ALTER_COLUMN_DROP_EXPRESSION, ALTER_TABLE_ALTER_COLUMN_DROP_IDENTITY, ALTER_TABLE_ALTER_COLUMN_DROP_NOT_NULL, ALTER_TABLE_ALTER_COLUMN_NOT_NULL, ALTER_TABLE_ALTER_COLUMN_ON_UPDATE, ALTER_TABLE_ALTER_COLUMN_RENAME, ALTER_TABLE_ALTER_COLUMN_SELECTIVITY, ALTER_TABLE_ALTER_COLUMN_VISIBILITY, 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_SYNONYM, 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_SYNONYM, DROP_TABLE, DROP_TRIGGER, DROP_USER, DROP_VIEW, EXECUTE, EXECUTE_IMMEDIATELY, EXPLAIN, EXPLAIN_ANALYZE, GRANT, HELP, 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

Constructor Summary

Constructors

Constructor	Description
Command(SessionLocal session, java.lang.String sql)

Method Summary

Modifier and Type	Method	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.
private void	commitIfNonTransactional()
ResultInterface	executeQuery(long maxrows, boolean scrollable)	Execute a query and return the result.
ResultWithGeneratedKeys	executeUpdate(java.lang.Object generatedKeysRequest)	Execute the statement
private long	filterConcurrentUpdate(DbException e, long start)
abstract java.util.Set<DbObject>	getDependencies()
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()
protected abstract boolean	isCurrentCommandADefineCommand()	Is the command we just tried to execute a DefineCommand (i.e.
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 ResultInterface	query(long 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.
void	setCanReuse(boolean canReuse)
(package private) void	setProgress(int state)
(package private) void	start()	Start the stopwatch.
void	stop()	Stop the command execution, release all locks and resources
java.lang.String	toString()
abstract ResultWithGeneratedKeys	update(java.lang.Object generatedKeysRequest)	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 SessionLocal session

The session.

startTimeNanos

protected long startTimeNanos

The last start time.

trace

private final Trace trace

The trace module.

cancel

private volatile boolean cancel

If this query was canceled.

sql

private final java.lang.String sql

canReuse

private boolean canReuse

Constructor Detail

Command

Command(SessionLocal session,
        java.lang.String sql)

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

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 abstract ResultWithGeneratedKeys update(java.lang.Object generatedKeysRequest)

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

Parameters:

generatedKeysRequest - false if generated keys are not needed, true if generated keys should be configured automatically, int[] to specify column indices to return generated keys from, or String[] to specify column names to return generated keys from

Returns:

the update count and generated keys, if any

Throws:

DbException - if the command is not an updating statement

query

public abstract ResultInterface query(long 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

start

void start()

Start the stopwatch.

setProgress

void setProgress(int state)

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

stop

public void stop()

Description copied from interface: CommandInterface

Stop the command execution, release all locks and resources

Specified by:

stop in interface CommandInterface

executeQuery

public ResultInterface executeQuery(long maxrows,
                                    boolean scrollable)

Execute a query and return the result. This method prepares everything and calls query(long) 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 ResultWithGeneratedKeys executeUpdate(java.lang.Object generatedKeysRequest)

Description copied from interface: CommandInterface

Execute the statement

Specified by:

executeUpdate in interface CommandInterface

Parameters:

generatedKeysRequest - null or false if generated keys are not needed, true if generated keys should be configured automatically, int[] to specify column indices to return generated keys from, or String[] to specify column names to return generated keys from

Returns:

the update count and generated keys, if any

commitIfNonTransactional

private void commitIfNonTransactional()

filterConcurrentUpdate

private long filterConcurrentUpdate(DbException e,
                                    long start)

close

public void close()

Description copied from interface: CommandInterface

Close the statement.

Specified by:

close in interface java.lang.AutoCloseable

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.

setCanReuse

public void setCanReuse(boolean canReuse)

getDependencies

public abstract java.util.Set<DbObject> getDependencies()

isCurrentCommandADefineCommand

protected abstract boolean isCurrentCommandADefineCommand()

Is the command we just tried to execute a DefineCommand (i.e. DDL).

Returns:

true if yes