Interface LockingClauseStrategy

@Incubating(since="7.1", group="dialect-locking") @SPI({USE,IMPLEMENT,SUPPLY}) public interface LockingClauseStrategy

Per-translation strategy for collecting lock targets and rendering statement-level pessimistic locking.

Some dialects do not use a FOR UPDATE (OF) to apply locks - e.g., they apply locks in the FROM clause. Such dialects would return a no-op version of this contract.

Some dialects support an additional FOR SHARE (OF) clause as well to acquire non-exclusive locks. That is also handled here, varied by the requested LockMode.

The translator uses each instance in two ordered phases:

  1. register roots and joins while traversing the from clause; and
  2. render the locking fragment after statement rendering reaches the database-specific clause position.

Implementations may retain state collected during the first phase, so an instance belongs to one translation and must not be cached or reused. Prefer composing LockingClauseRenderer through the standard strategy unless target collection itself differs.

Since:
8.0
See Also:
Implementation Specification:
Note that this is also used to determine and track which tables to lock even for cases (T-SQL e.g.) where a "locking clause" per-se won't be used. In such cases, only the first phase (along with shouldLockRoot() and shouldLockJoin()) have any impact.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    containsJoins()
    Whether registration encountered any join.
    boolean
    containsOuterJoins()
    Whether registration encountered an outer join.
    Collection<NavigablePath>
    getPathsToLock()
    The navigable paths selected for locking during registration.
    boolean
    registerJoin(TableGroupJoin join)
    Register the given table-group join during from-clause traversal.
    boolean
    registerRoot(TableGroup root)
    Register the given root table group during from-clause traversal.
    void
    render(SqlAppender sqlAppender)
    Render the locking fragment at the position selected by the translator.

  • Method Details

    • registerRoot

      boolean registerRoot(TableGroup root)
      Register the given root table group during from-clause traversal.
      Returns:
      whether the translator should render this root as locked

    • registerJoin

      boolean registerJoin(TableGroupJoin join)
      Register the given table-group join during from-clause traversal.
      Returns:
      whether the translator should render this join as locked

    • containsOuterJoins

      boolean containsOuterJoins()
      Whether registration encountered an outer join.

    • containsJoins

      boolean containsJoins()
      Whether registration encountered any join.

    • render

      void render(SqlAppender sqlAppender)
      Render the locking fragment at the position selected by the translator. A no-clause strategy performs no output.

    • getPathsToLock

      Collection<NavigablePath> getPathsToLock()
      The navigable paths selected for locking during registration.