| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.store.access.sort.SortBufferScan |
| 4 | |
| 5 | Copyright 1997, 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.access.sort; |
| 22 | |
| 23 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 24 | |
| 25 | import org.apache.derby.iapi.error.StandardException; |
| 26 | import org.apache.derby.iapi.store.access.ScanController; |
| 27 | import org.apache.derby.iapi.store.access.conglomerate.TransactionManager; |
| 28 | |
| 29 | /** |
| 30 | |
| 31 | A sort scan that just reads rows out of a sorter. |
| 32 | |
| 33 | **/ |
| 34 | |
| 35 | public class SortBufferScan extends SortScan |
| 36 | { |
| 37 | /** |
| 38 | The sorter we're returning rows from. |
| 39 | **/ |
| 40 | protected SortBuffer sortBuffer; |
| 41 | |
| 42 | /* |
| 43 | * Constructors. |
| 44 | */ |
| 45 | |
| 46 | SortBufferScan( |
| 47 | MergeSort sort, |
| 48 | TransactionManager tran, |
| 49 | SortBuffer sortBuffer, |
| 50 | boolean hold) |
| 51 | { |
| 52 | super(sort, tran, hold); |
| 53 | |
| 54 | if (SanityManager.DEBUG) |
| 55 | SanityManager.ASSERT(sortBuffer != null); |
| 56 | |
| 57 | this.sortBuffer = sortBuffer; |
| 58 | } |
| 59 | |
| 60 | /* |
| 61 | * Methods of MergeSortScan |
| 62 | */ |
| 63 | |
| 64 | /** |
| 65 | Move to the next position in the scan. |
| 66 | @see ScanController#next |
| 67 | **/ |
| 68 | public boolean next() |
| 69 | throws StandardException |
| 70 | { |
| 71 | if (SanityManager.DEBUG) |
| 72 | { |
| 73 | SanityManager.ASSERT( |
| 74 | sortBuffer != null, |
| 75 | "next() called on scan after scan was closed."); |
| 76 | } |
| 77 | |
| 78 | super.current = sortBuffer.removeFirst(); |
| 79 | return (super.current != null); |
| 80 | } |
| 81 | |
| 82 | /** |
| 83 | Close the scan. |
| 84 | **/ |
| 85 | public boolean closeForEndTransaction(boolean closeHeldScan) |
| 86 | { |
| 87 | if (closeHeldScan || !hold) |
| 88 | { |
| 89 | close(); |
| 90 | return(true); |
| 91 | } |
| 92 | else |
| 93 | { |
| 94 | return(false); |
| 95 | } |
| 96 | |
| 97 | } |
| 98 | |
| 99 | /** |
| 100 | Close the scan. |
| 101 | @see ScanController#close |
| 102 | **/ |
| 103 | public void close() |
| 104 | { |
| 105 | if (super.sort != null) |
| 106 | { |
| 107 | sort.doneScanning(this, sortBuffer); |
| 108 | sortBuffer = null; |
| 109 | } |
| 110 | super.close(); |
| 111 | } |
| 112 | |
| 113 | } |