org.jooq
Interface LockProvider

All Known Subinterfaces:

SelectQuery, SimpleSelectQuery<R>

public interface LockProvider

A query part (mostly a Select statement) providing the possibility of locking tables, rows using a FOR UPDATE clause

Author:

Lukas Eder

Method Summary

void	setForShare(boolean forShare) Sets the "FOR SHARE" flag onto the query This has been observed to be supported by any of these dialects: MySQL's InnoDB locking reads Postgres FOR UPDATE / FOR SHARE If your dialect does not support this clause, jOOQ will still render it, if you apply it to your query.
void	setForUpdate(boolean forUpdate) Sets the "FOR UPDATE" flag onto the query Native implementation This has been observed to be supported by any of these dialects:	void	setForUpdateNoWait() Some RDBMS allow for specifying the locking mode for the applied FOR UPDATE clause.
void	setForUpdateOf(Collection<? extends Field<?>> fields) Some RDBMS allow for specifying the fields that should be locked by the FOR UPDATE clause, instead of the full row.
void	setForUpdateOf(Field<?>... fields) Some RDBMS allow for specifying the fields that should be locked by the FOR UPDATE clause, instead of the full row.
void	setForUpdateOf(Table<?>... tables) Some RDBMS allow for specifying the tables that should be locked by the FOR UPDATE clause, instead of the full row.
void	setForUpdateSkipLocked() Some RDBMS allow for specifying the locking mode for the applied FOR UPDATE clause.
void	setForUpdateWait(int seconds) Some RDBMS allow for specifying the locking mode for the applied FOR UPDATE clause.

Method Detail

setForUpdate

void setForUpdate(boolean forUpdate)

Sets the "FOR UPDATE" flag onto the query

Native implementation

This has been observed to be supported by any of these dialects:

• DB2 FOR UPDATE and similar clauses
• Derby's FOR UPDATE clause
• H2's FOR UPDATE clause
• HSQLDB's FOR UPDATE clause
• MySQL's InnoDB locking reads
• Oracle's PL/SQL FOR UPDATE clause
• Postgres FOR UPDATE / FOR SHARE

Simulation

These dialects can simulate the FOR UPDATE clause using a cursor. The cursor is handled by the JDBC driver, at PreparedStatement construction time, when calling Connection.prepareStatement(String, int, int) with ResultSet.CONCUR_UPDATABLE. jOOQ handles simulation of a FOR UPDATE clause using CONCUR_UPDATABLE for these dialects:

• SQLDialect.CUBRID
• SQLDialect.SQLSERVER

Note: This simulation may not be efficient for large result sets!

Not supported

These dialects are known not to support the FOR UPDATE clause in regular SQL:

• SQLDialect.SQLITE

If your dialect does not support this clause, jOOQ will still render it, if you apply it to your query. This might then cause syntax errors reported either by your database or your JDBC driver.

You shouldn't combine this with setForShare(boolean)

Parameters:

forUpdate - The flag's value

setForUpdateOf

void setForUpdateOf(Field<?>... fields)

Some RDBMS allow for specifying the fields that should be locked by the FOR UPDATE clause, instead of the full row.

This automatically sets the setForUpdate(boolean) flag, and unsets the setForShare(boolean) flag, if it was previously set.

This has been observed to be natively supported by any of these dialects:

• DB2
• Derby
• H2
• HSQLDB
• Ingres
• Oracle
• Sybase

Note, that SQLDialect.DB2 has some stricter requirements regarding the updatability of fields. Refer to the DB2 documentation for further details

Parameters:

fields - The fields that should be locked

setForUpdateOf

void setForUpdateOf(Collection<? extends Field<?>> fields)

Some RDBMS allow for specifying the fields that should be locked by the FOR UPDATE clause, instead of the full row.

See Also:

setForUpdateOf(Field...)

setForUpdateOf

void setForUpdateOf(Table<?>... tables)

Some RDBMS allow for specifying the tables that should be locked by the FOR UPDATE clause, instead of the full row.

This automatically sets the setForUpdate(boolean) flag, and unsets the setForShare(boolean) flag, if it was previously set.

This has been observed to be natively supported by any of these dialects:

• Postgres
• H2
• HSQLDB
• Sybase

jOOQ simulates this by locking all known fields of [tables] for any of these dialects:

• DB2
• Derby
• Ingres
• Oracle

Parameters:

tables - The tables that should be locked

setForUpdateWait

void setForUpdateWait(int seconds)

Some RDBMS allow for specifying the locking mode for the applied FOR UPDATE clause. In this case, the session will wait for some seconds, before aborting the lock acquirement if the lock is not available.

This automatically sets the setForUpdate(boolean) flag, and unsets the setForShare(boolean) flag, if it was previously set.

This has been observed to be supported by any of these dialects:

• Oracle

Parameters:

seconds - The number of seconds to wait for a lock

setForUpdateNoWait

void setForUpdateNoWait()

Some RDBMS allow for specifying the locking mode for the applied FOR UPDATE clause. In this case, the session will not wait before aborting the lock acquirement if the lock is not available.

This automatically sets the setForUpdate(boolean) flag, and unsets the setForShare(boolean) flag, if it was previously set.

This has been observed to be supported by any of these dialects:

• Oracle

setForUpdateSkipLocked

void setForUpdateSkipLocked()

Some RDBMS allow for specifying the locking mode for the applied FOR UPDATE clause. In this case, the session will skip all locked rows from the select statement, whose lock is not available.

This automatically sets the setForUpdate(boolean) flag, and unsets the setForShare(boolean) flag, if it was previously set.

This has been observed to be supported by any of these dialects:

• Oracle

setForShare

void setForShare(boolean forShare)

Sets the "FOR SHARE" flag onto the query

This has been observed to be supported by any of these dialects:

• MySQL's InnoDB locking reads
• Postgres FOR UPDATE / FOR SHARE

If your dialect does not support this clause, jOOQ will still render it, if you apply it to your query. This might then cause syntax errors reported either by your database or your JDBC driver.

You shouldn't combine this with setForUpdate(boolean)

Parameters:

forShare - The flag's value