Class B2IRowLocking1

  • All Implemented Interfaces:
    BTreeLockingPolicy

    class B2IRowLocking1
    extends B2IRowLocking2
    implements BTreeLockingPolicy
    The btree locking policy which implements read uncommitted isolation level. It inherits all functionality from B2IRowLocking2 except that it does not get any read row locks (and thus does not release them). Note that table level and table level intent locking remains the same as B2IRowLocking2 as this is currently the way we prevent concurrent ddl from happening while a read uncommitted scanner is operating in the btree.
    • Method Detail

      • lockScanRow

        public boolean lockScanRow​(OpenBTree open_btree,
                                   BTreeRowPosition pos,
                                   FetchDescriptor lock_fetch_desc,
                                   DataValueDescriptor[] lock_template,
                                   RowLocation lock_row_loc,
                                   boolean previous_key_lock,
                                   boolean forUpdate,
                                   int lock_operation)
                            throws StandardException
        Lock a row as part of doing the scan.

        Lock the row at the given slot (or the previous row if slot is 0).

        If this routine returns true all locks were acquired while maintaining the latch on leaf. If this routine returns false, locks may or may not have been acquired, and the routine should be called again after the client has researched the tree to reget the latch on the appropriate page.

        Specified by:
        lockScanRow in interface BTreeLockingPolicy
        Overrides:
        lockScanRow in class B2IRowLockingRR
        Parameters:
        open_btree - The open_btree to associate latches with - used if routine has to scan backward.
        pos - The position of the row to lock.
        lock_template - A scratch area to use to read in rows.
        previous_key_lock - Is this a previous key lock call?
        forUpdate - Is the scan for update or for read only.
        lock_operation - For what operation are we requesting the lock, this should be one of the following 4 options: LOCK_READ [read lock], (LOCK_INS | LOCK_UPD) [ lock for insert], (LOCK_INSERT_PREVKEY | LOCK_UPD) [lock for previous key to insert], (LOCK_UPD) [lock for delete or replace]
        Returns:
        Whether locks were acquired without releasing latch on leaf.
        Throws:
        StandardException - Standard exception policy.
      • unlockScanRecordAfterRead

        public void unlockScanRecordAfterRead​(BTreeRowPosition pos,
                                              boolean forUpdate)
                                       throws StandardException
        Release read lock on a row. Because this is read uncommitted no S row locks will have been requested, thus none need be released. The only locks that need to be released are U locks requested if the scan was opened for update.
        Specified by:
        unlockScanRecordAfterRead in interface BTreeLockingPolicy
        Overrides:
        unlockScanRecordAfterRead in class B2IRowLocking2
        Parameters:
        pos - The position of the row to unlock.
        forUpdate - Is the scan for update or for read only.
        Throws:
        StandardException - Standard exception policy.