Package org.h2.command

Class Command

java.lang.Object

org.h2.command.Command

All Implemented Interfaces:

AutoCloseable, CommandInterface

Direct Known Subclasses:

CommandContainer

public abstract class Command
extends Object
implements CommandInterface

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

Field Summary

Fields

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

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_TYPE, 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_MATERIALIZED_VIEW, 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_MATERIALIZED_VIEW, 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, REFRESH_MATERIALIZED_VIEW, 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

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.
BatchResult	executeBatchUpdate(ArrayList<Value[]> batchParameters, Object generatedKeysRequest)	Executes the statement with multiple sets of parameters.
ResultInterface	executeQuery(long maxrows, int fetchSize, boolean scrollable)	Execute a query and return the result.
ResultWithGeneratedKeys	executeUpdate(Object generatedKeysRequest)	Execute the statement
protected final Database	getDatabase()
abstract Set<DbObject>	getDependencies()	Collect all database objects, this command depends on
final ResultInterface	getMetaData()	Get an empty result set containing the meta data of the result.
abstract ArrayList<? extends ParameterInterface>	getParameters()	Get the list of parameters.
abstract void	invalidateCachedResult(Table reason)	Clear cached results of all prepared statements, which depends on a given table
boolean	isCacheable()
abstract boolean	isQuery()	Check if this command is a query.
abstract boolean	isReadOnly()	Check if this command is read only.
protected abstract boolean	isRetryable()	Checks if this command can be repeated on locking failure.
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 metadata.
void	reuse()	The command is now re-used, therefore reset the canReuse flag, and the parameter values.
void	stop(boolean commitIfAutoCommit)	Stop the command execution, release all locks and resources.
String	toString()
abstract ResultWithGeneratedKeys	update(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 Details

session

protected final SessionLocal session

The session.

startTimeNanos

protected long startTimeNanos

The last start time.

Method Details

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 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 metadata.

Returns:

an empty result set

update

public abstract ResultWithGeneratedKeys update(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

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(boolean commitIfAutoCommit)

Description copied from interface: CommandInterface

Stop the command execution, release all locks and resources.

Specified by:

stop in interface CommandInterface

Parameters:

commitIfAutoCommit - commit the session if auto-commit is enabled

executeQuery

public ResultInterface executeQuery(long maxrows,
 int fetchSize,
 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

fetchSize - ignored by local commands

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

Returns:

the result set

executeUpdate

public ResultWithGeneratedKeys executeUpdate(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

executeBatchUpdate

public BatchResult executeBatchUpdate(ArrayList<Value[]> batchParameters,
 Object generatedKeysRequest)

Description copied from interface: CommandInterface

Executes the statement with multiple sets of parameters.

Specified by:

executeBatchUpdate in interface CommandInterface

Parameters:

batchParameters - batch 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:

result of batch execution

close

public void close()

Description copied from interface: CommandInterface

Close the statement.

Specified by:

close in interface 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 String toString()

Overrides:

toString in class 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.

getDependencies

public abstract Set<DbObject> getDependencies()

Collect all database objects, this command depends on

Returns:

Set of dependencies

invalidateCachedResult

public abstract void invalidateCachedResult(Table reason)

Clear cached results of all prepared statements, which depends on a given table

Parameters:

reason - table causing invalidation

isRetryable

protected abstract boolean isRetryable()

Checks if this command can be repeated on locking failure.

Returns:

true if this command can be repeated on locking failure

getDatabase

protected final Database getDatabase()