| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.store.raw.xact.RowLocking3Escalate |
| 4 | |
| 5 | Copyright 1998, 2004 The Apache Software Foundation or its licensors, as applicable. |
| 6 | |
| 7 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | you may not use this file except in compliance with the License. |
| 9 | You may obtain a copy of the License at |
| 10 | |
| 11 | http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | |
| 13 | Unless required by applicable law or agreed to in writing, software |
| 14 | distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | See the License for the specific language governing permissions and |
| 17 | limitations under the License. |
| 18 | |
| 19 | */ |
| 20 | |
| 21 | package org.apache.derby.impl.store.raw.xact; |
| 22 | |
| 23 | import org.apache.derby.iapi.services.locks.LockFactory; |
| 24 | import org.apache.derby.iapi.services.locks.Latch; |
| 25 | |
| 26 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 27 | |
| 28 | import org.apache.derby.iapi.store.raw.ContainerHandle; |
| 29 | import org.apache.derby.iapi.store.raw.ContainerLock; |
| 30 | import org.apache.derby.iapi.store.raw.RecordHandle; |
| 31 | import org.apache.derby.iapi.store.raw.Transaction; |
| 32 | |
| 33 | import org.apache.derby.iapi.error.StandardException; |
| 34 | |
| 35 | |
| 36 | /** |
| 37 | A locking policy that implements row level locking with isolation degree 3. |
| 38 | |
| 39 | @see org.apache.derby.iapi.store.raw.LockingPolicy |
| 40 | */ |
| 41 | public class RowLocking3Escalate extends ContainerLocking3 |
| 42 | { |
| 43 | protected RowLocking3Escalate(LockFactory lf) |
| 44 | { |
| 45 | super(lf); |
| 46 | } |
| 47 | |
| 48 | /** |
| 49 | * Escalates Row Locking 3 to Container Locking 3. |
| 50 | * <p> |
| 51 | * This call is made by code which tracks the number of locks on a |
| 52 | * container. When the number of locks exceeds the escalate threshold |
| 53 | * the caller creates this new locking policy, calls lockContainer(), |
| 54 | * and substitues it for the old locking policy. The lockContainer call |
| 55 | * determines which table lock to get (S or X), gets that table lock, and |
| 56 | * then releases the row locks on the table. |
| 57 | * |
| 58 | * It is assumed that this is called on a open container for lock only. |
| 59 | * <p> |
| 60 | * |
| 61 | * @param t Transaction to associate lock with. |
| 62 | * @param container Container to lock. |
| 63 | * @param waitForLock Ignored - will never wait for a lock. |
| 64 | * @param forUpdate Ignored, mode determined from current lock state. |
| 65 | * |
| 66 | * @return true if the lock was obtained, false if it wasn't. |
| 67 | * False should only be returned if the waitForLock policy was set to |
| 68 | * "false," and the lock was unavailable. |
| 69 | * |
| 70 | * @exception StandardException Standard exception policy. |
| 71 | **/ |
| 72 | public boolean lockContainer( |
| 73 | Transaction t, |
| 74 | ContainerHandle container, |
| 75 | boolean waitForLock, |
| 76 | boolean forUpdate) |
| 77 | throws StandardException |
| 78 | { |
| 79 | forUpdate = false; |
| 80 | |
| 81 | // If an IX lock exists then escalate to X table lock, else escalate |
| 82 | // to S table lock. |
| 83 | if (lf.isLockHeld( |
| 84 | t.getCompatibilitySpace(), t, |
| 85 | container.getId(), ContainerLock.CIX)) |
| 86 | { |
| 87 | forUpdate = true; |
| 88 | } |
| 89 | |
| 90 | // Get the new X or S table lock. |
| 91 | boolean gotLock = |
| 92 | super.lockContainer(t, container, waitForLock, forUpdate); |
| 93 | |
| 94 | if (!gotLock) |
| 95 | return false; |
| 96 | |
| 97 | // now remove all matching ROW locks, this is done using the special |
| 98 | // EscalateContainerKey() class which through the Matchable interface |
| 99 | // only matches row locks of this container. |
| 100 | lf.unlockGroup( |
| 101 | t.getCompatibilitySpace(), t, |
| 102 | new EscalateContainerKey(container.getId())); |
| 103 | |
| 104 | if (SanityManager.DEBUG) |
| 105 | { |
| 106 | SanityManager.ASSERT( |
| 107 | lf.isLockHeld( |
| 108 | t.getCompatibilitySpace(), t, |
| 109 | container.getId(), |
| 110 | (forUpdate ? ContainerLock.CX : ContainerLock.CS)), |
| 111 | "Covering table lock (" + |
| 112 | (forUpdate ? ContainerLock.CX : ContainerLock.CS) + |
| 113 | " is not held after lock escalation."); |
| 114 | } |
| 115 | |
| 116 | return true; |
| 117 | } |
| 118 | } |