| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.store.access.sort.SortBufferRowSource |
| 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.access.sort; |
| 22 | |
| 23 | import org.apache.derby.iapi.reference.SQLState; |
| 24 | |
| 25 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 26 | import org.apache.derby.iapi.error.StandardException; |
| 27 | import org.apache.derby.iapi.store.access.RowSource; |
| 28 | import org.apache.derby.iapi.store.access.SortObserver; |
| 29 | import org.apache.derby.iapi.types.RowLocation; |
| 30 | import org.apache.derby.iapi.store.access.conglomerate.ScanControllerRowSource; |
| 31 | import org.apache.derby.iapi.store.access.conglomerate.TransactionManager; |
| 32 | import org.apache.derby.iapi.store.access.ScanController; |
| 33 | |
| 34 | import org.apache.derby.iapi.types.DataValueDescriptor; |
| 35 | |
| 36 | import org.apache.derby.iapi.services.io.FormatableBitSet; |
| 37 | |
| 38 | /** |
| 39 | Wrapping the output of a SortBuffer in a RowSource for the benefit of the |
| 40 | createAndLoadConglomerate and loadConglomerate interface. |
| 41 | |
| 42 | Scan implements ScanController, this class just implements the |
| 43 | RowSource interface. |
| 44 | |
| 45 | */ |
| 46 | public class SortBufferRowSource extends Scan |
| 47 | implements ScanControllerRowSource |
| 48 | { |
| 49 | /** |
| 50 | The Sort buffer where rows come from |
| 51 | **/ |
| 52 | SortBuffer sortBuffer = null; |
| 53 | |
| 54 | /** |
| 55 | The TransactionManager that opened this scan. |
| 56 | **/ |
| 57 | protected TransactionManager tran = null; |
| 58 | |
| 59 | private int maxFreeListSize; |
| 60 | private boolean writingToDisk; |
| 61 | private SortObserver sortObserver; |
| 62 | |
| 63 | /* |
| 64 | * Constructors. |
| 65 | */ |
| 66 | |
| 67 | SortBufferRowSource( |
| 68 | SortBuffer sortBuffer, |
| 69 | TransactionManager tran, |
| 70 | SortObserver sortObserver, |
| 71 | boolean writingToDisk, |
| 72 | int maxFreeListSize) |
| 73 | { |
| 74 | super(); |
| 75 | this.sortBuffer = sortBuffer; |
| 76 | this.tran = tran; |
| 77 | this.sortObserver = sortObserver; |
| 78 | this.writingToDisk = writingToDisk; |
| 79 | this.maxFreeListSize = maxFreeListSize; |
| 80 | } |
| 81 | |
| 82 | /* Private/Protected methods of This class: */ |
| 83 | /* Public Methods of This class: */ |
| 84 | /* Public Methods of RowSource class: */ |
| 85 | |
| 86 | public DataValueDescriptor[] getNextRowFromRowSource() |
| 87 | { |
| 88 | if (sortBuffer == null) // has been closed |
| 89 | return null; |
| 90 | |
| 91 | DataValueDescriptor[] retval = sortBuffer.removeFirst(); |
| 92 | |
| 93 | // Return the removed object to the free DataValueDescriptor[] |
| 94 | if (retval != null && writingToDisk) |
| 95 | { |
| 96 | sortObserver.addToFreeList(retval, maxFreeListSize); |
| 97 | } |
| 98 | return retval; |
| 99 | } |
| 100 | |
| 101 | public boolean needsRowLocation() |
| 102 | { |
| 103 | return false; |
| 104 | } |
| 105 | |
| 106 | /** |
| 107 | * @see RowSource#needsToClone |
| 108 | */ |
| 109 | public boolean needsToClone() |
| 110 | { |
| 111 | return false; |
| 112 | } |
| 113 | |
| 114 | public void rowLocation(RowLocation rl) |
| 115 | { |
| 116 | if (SanityManager.DEBUG) |
| 117 | SanityManager.THROWASSERT("unexpected call to RowSource.rowLocation"); |
| 118 | } |
| 119 | |
| 120 | |
| 121 | /** |
| 122 | All columns are always set from a sorter |
| 123 | */ |
| 124 | public FormatableBitSet getValidColumns() |
| 125 | { |
| 126 | return null; |
| 127 | } |
| 128 | |
| 129 | /** |
| 130 | Close the scan |
| 131 | */ |
| 132 | public void close() |
| 133 | { |
| 134 | if (sortBuffer != null) |
| 135 | { |
| 136 | sortBuffer.close(); |
| 137 | sortBuffer = null; |
| 138 | } |
| 139 | tran.closeMe(this); |
| 140 | } |
| 141 | |
| 142 | /** |
| 143 | Close the scan |
| 144 | */ |
| 145 | public boolean closeForEndTransaction(boolean closeHeldScan) |
| 146 | { |
| 147 | if (SanityManager.DEBUG) |
| 148 | SanityManager.ASSERT( |
| 149 | closeHeldScan, |
| 150 | "Sort scan should not be held open across commit."); |
| 151 | |
| 152 | close(); |
| 153 | return(true); |
| 154 | } |
| 155 | |
| 156 | /** |
| 157 | Close the rowSource |
| 158 | */ |
| 159 | public void closeRowSource() |
| 160 | { |
| 161 | close(); |
| 162 | } |
| 163 | |
| 164 | /* |
| 165 | * Disable illegal and dangerous scan controller interface call |
| 166 | */ |
| 167 | public boolean next() throws StandardException |
| 168 | { |
| 169 | throw StandardException.newException( |
| 170 | SQLState.SORT_IMPROPER_SCAN_METHOD); |
| 171 | } |
| 172 | |
| 173 | /** |
| 174 | * Fetch the row at the current position of the Scan and does not apply the |
| 175 | * qualifiers. |
| 176 | * |
| 177 | * This method will always throw an exception. |
| 178 | * (SQLState.SORT_IMPROPER_SCAN_METHOD) |
| 179 | * |
| 180 | * @see ScanController#fetchWithoutQualify |
| 181 | **/ |
| 182 | public void fetchWithoutQualify(DataValueDescriptor[] result) |
| 183 | throws StandardException |
| 184 | { |
| 185 | throw StandardException.newException( |
| 186 | SQLState.SORT_IMPROPER_SCAN_METHOD); |
| 187 | } |
| 188 | |
| 189 | /** |
| 190 | * Fetch the row at the current position of the Scan. |
| 191 | * |
| 192 | * @see ScanController#fetch |
| 193 | **/ |
| 194 | public void fetch(DataValueDescriptor[] result) throws StandardException |
| 195 | { |
| 196 | throw StandardException.newException( |
| 197 | SQLState.SORT_IMPROPER_SCAN_METHOD); |
| 198 | } |
| 199 | |
| 200 | public final boolean fetchNext(DataValueDescriptor[] row) |
| 201 | throws StandardException |
| 202 | { |
| 203 | throw StandardException.newException( |
| 204 | SQLState.SORT_IMPROPER_SCAN_METHOD); |
| 205 | } |
| 206 | |
| 207 | } |