Source Code Cross Referenced for RowLocking3Escalate.java in  » Database-DBMS » db-derby-10.2 » org » apache » derby » impl » store » raw » xact » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Database DBMS » db derby 10.2 » org.apache.derby.impl.store.raw.xact 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:
003:           Derby - Class org.apache.derby.impl.store.raw.xact.RowLocking3Escalate
004:
005:           Licensed to the Apache Software Foundation (ASF) under one or more
006:           contributor license agreements.  See the NOTICE file distributed with
007:           this work for additional information regarding copyright ownership.
008:           The ASF licenses this file to you under the Apache License, Version 2.0
009:           (the "License"); you may not use this file except in compliance with
010:           the License.  You may obtain a copy of the License at
011:
012:              http://www.apache.org/licenses/LICENSE-2.0
013:
014:           Unless required by applicable law or agreed to in writing, software
015:           distributed under the License is distributed on an "AS IS" BASIS,
016:           WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017:           See the License for the specific language governing permissions and
018:           limitations under the License.
019:
020:         */
021:
022:        package org.apache.derby.impl.store.raw.xact;
023:
024:        import org.apache.derby.iapi.services.locks.LockFactory;
025:        import org.apache.derby.iapi.services.locks.Latch;
026:
027:        import org.apache.derby.iapi.services.sanity.SanityManager;
028:
029:        import org.apache.derby.iapi.store.raw.ContainerHandle;
030:        import org.apache.derby.iapi.store.raw.ContainerLock;
031:        import org.apache.derby.iapi.store.raw.RecordHandle;
032:        import org.apache.derby.iapi.store.raw.Transaction;
033:
034:        import org.apache.derby.iapi.error.StandardException;
035:
036:        /**
037:         A locking policy that implements row level locking with isolation degree 3.
038:
039:         @see org.apache.derby.iapi.store.raw.LockingPolicy
040:         */
041:        public class RowLocking3Escalate extends ContainerLocking3 {
042:            protected RowLocking3Escalate(LockFactory lf) {
043:                super (lf);
044:            }
045:
046:            /**
047:             * Escalates Row Locking 3 to Container Locking 3.
048:             * <p>
049:             * This call is made by code which tracks the number of locks on a 
050:             * container. When the number of locks exceeds the escalate threshold
051:             * the caller creates this new locking policy, calls lockContainer(), 
052:             * and substitues it for the old locking policy.  The lockContainer call
053:             * determines which table lock to get (S or X), gets that table lock, and
054:             * then releases the row locks on the table.
055:             *
056:             * It is assumed that this is called on a open container for lock only.
057:             * <p>
058:             *
059:             * @param t            Transaction to associate lock with.
060:             * @param container    Container to lock.
061:             * @param waitForLock  Ignored - will never wait for a lock.
062:             * @param forUpdate    Ignored, mode determined from current lock state.
063:             *
064:             * @return true if the lock was obtained, false if it wasn't. 
065:             *   False should only be returned if the waitForLock policy was set to
066:             *  "false," and the lock was unavailable.
067:             *
068:             * @exception  StandardException  Standard exception policy.
069:             **/
070:            public boolean lockContainer(Transaction t,
071:                    ContainerHandle container, boolean waitForLock,
072:                    boolean forUpdate) throws StandardException {
073:                forUpdate = false;
074:
075:                // If an IX lock exists then escalate to X table lock, else escalate
076:                // to S table lock.
077:                if (lf.isLockHeld(t.getCompatibilitySpace(), t, container
078:                        .getId(), ContainerLock.CIX)) {
079:                    forUpdate = true;
080:                }
081:
082:                // Get the new X or S table lock.
083:                boolean gotLock = super .lockContainer(t, container,
084:                        waitForLock, forUpdate);
085:
086:                if (!gotLock)
087:                    return false;
088:
089:                // now remove all matching ROW locks, this is done using the special
090:                // EscalateContainerKey() class which through the Matchable interface
091:                // only matches row locks of this container.
092:                lf.unlockGroup(t.getCompatibilitySpace(), t,
093:                        new EscalateContainerKey(container.getId()));
094:
095:                if (SanityManager.DEBUG) {
096:                    SanityManager.ASSERT(lf.isLockHeld(t
097:                            .getCompatibilitySpace(), t, container.getId(),
098:                            (forUpdate ? ContainerLock.CX : ContainerLock.CS)),
099:                            "Covering table lock ("
100:                                    + (forUpdate ? ContainerLock.CX
101:                                            : ContainerLock.CS)
102:                                    + " is not held after lock escalation.");
103:                }
104:
105:                return true;
106:            }
107:        }
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