| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.store.raw.xact.RowLockingRR |
| 4 | |
| 5 | Copyright 2000, 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 | package org.apache.derby.impl.store.raw.xact; |
| 21 | |
| 22 | import org.apache.derby.iapi.services.locks.LockFactory; |
| 23 | import org.apache.derby.iapi.services.locks.C_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.LockingPolicy; |
| 31 | import org.apache.derby.iapi.store.raw.RecordHandle; |
| 32 | import org.apache.derby.iapi.store.raw.RowLock; |
| 33 | import org.apache.derby.iapi.store.raw.Transaction; |
| 34 | |
| 35 | import org.apache.derby.iapi.error.StandardException; |
| 36 | |
| 37 | |
| 38 | /** |
| 39 | A locking policy that implements row level locking with repeatable read |
| 40 | isolation. Since phantom protection with previous key locking is actually |
| 41 | handled by the upper level access methods, the only difference in repeatable |
| 42 | read is that read locks are of type RowLock.RS2. This type will not |
| 43 | conflict with a previous key insert lock. |
| 44 | |
| 45 | @see org.apache.derby.iapi.store.raw.LockingPolicy |
| 46 | */ |
| 47 | public class RowLockingRR extends RowLocking3 |
| 48 | { |
| 49 | |
| 50 | protected RowLockingRR(LockFactory lf) |
| 51 | { |
| 52 | super(lf); |
| 53 | } |
| 54 | |
| 55 | protected RowLock getReadLockType() |
| 56 | { |
| 57 | return(RowLock.RS2); |
| 58 | } |
| 59 | |
| 60 | protected RowLock getUpdateLockType() |
| 61 | { |
| 62 | return(RowLock.RU2); |
| 63 | } |
| 64 | |
| 65 | protected RowLock getWriteLockType() |
| 66 | { |
| 67 | return(RowLock.RX2); |
| 68 | } |
| 69 | |
| 70 | /** |
| 71 | * Unlock a record after it has been locked for read. |
| 72 | * <p> |
| 73 | * In repeatable read only unlock records which "did not qualify". For |
| 74 | * example in a query like "select * from foo where a = 1" on a table |
| 75 | * with no index it is only necessary to hold locks on rows where a=1, but |
| 76 | * in the process of finding those rows the system will get locks on other |
| 77 | * rows to verify they are committed before applying the qualifier. Those |
| 78 | * locks can be released under repeatable read isolation. |
| 79 | * <p> |
| 80 | * |
| 81 | * @exception StandardException Standard exception policy. |
| 82 | **/ |
| 83 | public void unlockRecordAfterRead( |
| 84 | Transaction t, |
| 85 | ContainerHandle container_handle, |
| 86 | RecordHandle record, |
| 87 | boolean forUpdate, |
| 88 | boolean row_qualified) |
| 89 | throws StandardException |
| 90 | { |
| 91 | if (!row_qualified) |
| 92 | { |
| 93 | Object qualifier = forUpdate ? RowLock.RU2 : RowLock.RS2; |
| 94 | |
| 95 | int count = |
| 96 | lf.unlock(t.getCompatibilitySpace(), t, record, qualifier); |
| 97 | |
| 98 | if (SanityManager.DEBUG) |
| 99 | { |
| 100 | // in the case of lock escalation the count could be 0. |
| 101 | if (!(count == 1 || count == 0)) |
| 102 | { |
| 103 | SanityManager.THROWASSERT( |
| 104 | "count = " + count + |
| 105 | "record.getContainerId() = " + record.getContainerId()); |
| 106 | } |
| 107 | } |
| 108 | } |
| 109 | } |
| 110 | |
| 111 | } |