This class is created and owned by the concrete application, but is passed into and returned from the generic code when lock calls are made. Concrete implementations which do not need lock calls can just pass a null pointer where a BTreeLockingPolicy is requested.
There are 2 types of lock interfaces, lockScan*() and lockNonScan*().
The lockScan*() interfaces save the key for the current scan position before
giving up the latch on the page if they have to wait for a row lock. The
callers can reposition the scan using the saved key by calling
BTreeScan.reposition() if such a situation occurs. Then the latches
are reobtained, possibly on a different page if the current key has been moved
to another page in the meantime. Upon return from these interfaces
the row lock requested is guaranteed to have been obtained on the correct
key for the row requested. These interfaces handle the special case of
unique indexes where the RowLocation can change while waiting on the lock
(see implementation for details), basically the lock is retryed after waiting
if the RowLocation has changed.
The lockNonScan*() interfaces do not save the current scan position. If these routines return that the latch was released while waiting to obtain the lock, then the caller must requeue the lock request after taking appropriate action. This action usually involves researching the tree to make sure that the correct key is locked with latches held. These interfaces do not handle the special case of unique indexes where the RowLocation can change while waiting on the lock, as the row may disappear when the latch is released to wait on the lock - thus it is necessary that the caller retry the lock if the interface returns that the latch was released.
| Modifier and Type | Method and Description |
|---|---|
| public boolean | lockNonScanPreviousRow(LeafControlRow
Latched current leaf where "current" key is. current_leaf, int The slot of row on "current_leaf" current_slot, FetchDescriptor lock_fetch_desc, DataValueDescriptor[] Empty full template row, to read row into. lock_template, RowLocation lock_row_loc, OpenBTree The open_btree to associate latches with -
used if routine has to scan backward. open_btree, int 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] lock_operation, int For what duration should the lock be held,
if INSTANT_DURATION, then the routine will
guarantee that lock was acquired while holding
the latch, but then immediately release the
lock. If COMMIT_DURATION or MANUAL_DURATION
then the lock be held when routine returns
successfully. lock_duration)Lock the previous key. |
| public boolean | lockNonScanRow(BTree
The conglomerate we are locking. btree, LeafControlRow If non-null, this leaf is unlatched if the
routine has to wait on the lock. current_leaf, LeafControlRow If non-null, this leaf is unlatched if the
routine has to wait on the lock. aux_leaf, DataValueDescriptor[] In memory, objectified "current" row. current_row, int 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] lock_operation)Lock a btree row (row in memory). |
| public boolean | Returns: Whether locks were acquired without releasing latch on leaf.The control row of the current leaf to lock. leaf, int The slot position of the row to lock. slot, FetchDescriptor lock_fetch_desc, DataValueDescriptor[] A scratch area to use to read in rows. lock_template, RowLocation lock_row_loc, int 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] lock_operation)Lock the row at the given slot. |
| public boolean | lockScanCommittedDeletedRow(OpenBTree
The conglomerate we are locking. open_btree, LeafControlRow The leaf page with the row to lock. leaf, DataValueDescriptor[] Empty full template row, to read row into. template, FetchDescriptor lock_fetch_desc, int The slot of row on "current_leaf" slot_no)Lock a btree row to determine if it is a committed deleted row. |
| public boolean | Returns: Whether locks were acquired without releasing latch on leaf.The open_btree to associate latches with -
used if routine has to scan backward. open_btree, BTreeRowPosition Description of position of row to lock. pos, FetchDescriptor lock_fetch_desc, DataValueDescriptor[] A scratch area to use to read in rows. lock_template, RowLocation lock_row_loc, boolean Is this a previous key lock call? previous_key_lock, boolean Is the scan for update or for read only. forUpdate, int 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] lock_operation)Lock a row as part of doing the scan. |
| public void | unlockScanRecordAfterRead(BTreeRowPosition
Data structure that defines the current position
in the scan to be unlocked. pos, boolean Is the scan for update or for read only. forUpdate)Release read lock on a row. |
| lockNonScanPreviousRow | back to summary |
|---|---|
| public boolean lockNonScanPreviousRow(LeafControlRow current_leaf, int current_slot, FetchDescriptor lock_fetch_desc, DataValueDescriptor[] lock_template, RowLocation lock_row_loc, OpenBTree open_btree, int lock_operation, int lock_duration) throws StandardException Lock the previous key. Given the current latched page and slot number, lock the logically previous key in the table. There are 3 cases: slotnumber > 1 - just lock (slotnumber - 1) (slotnumber == 1) && (leftmost leaf) - this is the first key in the table, so lock a "magic" FIRSTKEY. (slotnumber == 1) && !(leftmost leaf)- traverse left in the tree looking for a previous key. On successful return from this routine appropriate locking will have been done. All locks and latches are requested nowait, if any lock/latch cannot be granted this routine releases the current_leaf latch and any latches it may have acquired and returns "false." All extra latches that may have been gotten will have been released. This routine will find the "previous row" to the (current_leaf, current_slot), walking left in the tree as necessary, and first request the lock on that row NOWAIT. If that lock can not be granted, then it will release all latches that it has acquired up to that point including the latched current_leaf passed into the routine, and request the lock WAIT. Once the lock has been granted the routine will return and it is up to the caller to research the tree to find where the current position may have ended up. For instance in the case of insert once the current latch is released, the correct page to do the insert may no longer be where the original scan found it. If routine returns true, lock was granted NOWAIT, current leaf remains latched, and was never unlatched. If routine returns false, lock was granted WAIT, current leaf is not latched, row may have moved in the btree so caller must research to find the row.
| |
| lockNonScanRow | back to summary |
|---|---|
| public boolean lockNonScanRow(BTree btree, LeafControlRow current_leaf, LeafControlRow aux_leaf, DataValueDescriptor[] current_row, int lock_operation) throws StandardException Lock a btree row (row in memory). Meant to be used if caller has the entire row objectified. Lock a btree row, enforcing the standard lock/latch protocol. On return the row is locked. Return status indicates if the lock was waited for, which will mean a latch was dropped while waiting. In general a false status means that the caller will either have to research the tree unless some protocol has been implemented that insures that the row will not have moved while the latch was dropped. This routine request a row lock NOWAIT on the in-memory row "current_row.". If the lock is granted the routine will return true. If the lock cannot be granted NOWAIT, then the routine will release the latch on "current_leaf" (if current_leaf is non-null) and "aux_leaf" (if aux_leaf is non-null), and then it will request a WAIT lock on the row.
| |
| lockNonScanRowOnPage | back to summary |
|---|---|
| public boolean lockNonScanRowOnPage(LeafControlRow leaf, int slot, FetchDescriptor lock_fetch_desc, DataValueDescriptor[] lock_template, RowLocation lock_row_loc, int lock_operation) throws StandardException Lock the row at the given slot. 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.
| |
| lockScanCommittedDeletedRow | back to summary |
|---|---|
| public boolean lockScanCommittedDeletedRow(OpenBTree open_btree, LeafControlRow leaf, DataValueDescriptor[] template, FetchDescriptor lock_fetch_desc, int slot_no) throws StandardException Lock a btree row to determine if it is a committed deleted row. Request an exclusive lock on the row located at the given slot, NOWAIT. Return true if the lock is granted, otherwise false.
| |
| lockScanRow | back to summary |
|---|---|
| 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.
| |
| unlockScanRecordAfterRead | back to summary |
|---|---|
| public void unlockScanRecordAfterRead(BTreeRowPosition pos, boolean forUpdate) throws StandardException Release read lock on a row.
| |