| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.sql.conn.TempTableInfo |
| 4 | |
| 5 | Copyright 2003, 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.sql.conn; |
| 22 | |
| 23 | import org.apache.derby.iapi.error.StandardException; |
| 24 | import org.apache.derby.iapi.sql.dictionary.TableDescriptor; |
| 25 | |
| 26 | //this class is for temporary tables. The information kept here is necessary to implement the rollback |
| 27 | //and commit behavior for temporary tables. |
| 28 | |
| 29 | /** |
| 30 | The temp tables will have following data structure |
| 31 | TableDescriptor |
| 32 | Declared in savepoint level |
| 33 | Dropped in savepoint level |
| 34 | Modified in savepoint level |
| 35 | |
| 36 | The actual logic |
| 37 | |
| 38 | LanguageConnectionContext will keep the "current savepoint level". At any point in |
| 39 | time, this is the total number of savepoints defined for a transaction. |
| 40 | At the start of any new transaction, the "current savepoint level" will be set to 0. |
| 41 | |
| 42 | Everytime a new user defined savepoint is set, store returns the total number of savepoints |
| 43 | for the connection at that point. |
| 44 | For eg, in a new transaction, |
| 45 | "current savepoint level' will be 0. When the first savepoint is set, store will return |
| 46 | 1 and "current savepoint level" will be set to 1. For next savepoint, store will return 2 and so on |
| 47 | and so forth. |
| 48 | |
| 49 | When language calls rollback or release of a savepoint, store will again return the total number of savepoints |
| 50 | for the connection after rollback or release and we will set "current savepoint level" to that number. For eg, |
| 51 | start tran ("current savepoint level"=0) |
| 52 | set savepoint 1 ("current savepoint level"=1) |
| 53 | set savepoint 2 ("current savepoint level"=2) |
| 54 | set savepoint 3 ("current savepoint level"=3) |
| 55 | set savepoint 4 ("current savepoint level"=4) |
| 56 | release savepoint 3 ("current savepoint level"=2) |
| 57 | rollback savepoint 1 ("current savepoint level"=0) |
| 58 | |
| 59 | If the temporary table was declared with ON ROLLBACK DELETE ROWS and contents of that temporary table |
| 60 | were modified in a transaction or within a savepoint unit, then we keep track of that by saving the |
| 61 | savepoint level in dataModifiedInSavepointLevel. This information will be used at rollback of savepoint or transaction. |
| 62 | Also, when a savepoint is released, we check if the table was modified in any of the savepoints that |
| 63 | are getting released. If yes, then we put the current savepoint level as dataModifiedInSavepointLevel. |
| 64 | eg |
| 65 | start tran ("current savepoint level"=0) |
| 66 | declare temp table 0 ON ROLLBACK DELETE ROWS("declared in savepoint level"=0, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 67 | commit (temp table 0 ("declared in savepoint level"=-1, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1)) |
| 68 | start tran ("current savepoint level = 0) |
| 69 | temp table 0 ("declared in savepoint level"=-1, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 70 | set savepoint 1("current savepoint level = 1") |
| 71 | temp table 0 ("declared in savepoint level"=-1, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 72 | set savepoint 2("current savepoint level = 2") |
| 73 | delete 1 row from temp table 0 |
| 74 | temp table 0 ("declared in savepoint level"=-1, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=2) |
| 75 | release savepoint 2 ("current savepoint level"=1) and reset the modified in savepoint level as follows |
| 76 | temp table 0 ("declared in savepoint level"=-1, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=1) |
| 77 | rollback ("current savepoint level"=0) All the rows from the temp table 0 will be removed |
| 78 | At the time of commit, we set dataModifiedInSavepointLevel to -1. |
| 79 | At the time of rollback (transaction / savepoint), first we check if the table was modified in the unit of work |
| 80 | getting rolled back. If yes, then we delete all the data from the temp table and we set dataModifiedInSavepointLevel to -1. |
| 81 | |
| 82 | When language calls release of a savepoint, store will again return the total number of savepoints |
| 83 | in the system after release. We will go through all the temp tables and reset their declared or |
| 84 | dropped or modified in savepoint level to the value returned by the release savepoint if those tables had their |
| 85 | declared or dropped or modified in savepoint levels higher than what was returned by the release savepoint. |
| 86 | eg |
| 87 | start tran ("current savepoint level"=0) |
| 88 | declare temp table 0 ("declared in savepoint level"=0, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 89 | set savepoint 1("current savepoint level = 1") |
| 90 | declare temp table 1 ("declared in savepoint level"=1, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 91 | set savepoint 2("current savepoint level = 2") |
| 92 | declare temp table 2 ("declared in savepoint level"=2, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 93 | release savepoint 1 ("current savepoint level"=0) and reset the savepoint levels as follows |
| 94 | temp table 1 ("declared in savepoint level"=0, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 95 | temp table 2 ("declared in savepoint level"=0, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 96 | set savepoint 3("current savepoint level = 1") |
| 97 | rollback savepoint 3 ("current savepoint level"=0) and temp table info will look as follows |
| 98 | temp table 0 ("declared in savepoint level"=0, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 99 | temp table 1 ("declared in savepoint level"=0, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 100 | temp table 2 ("declared in savepoint level"=0, "dropped in savepoint level"=-1, "dataModifiedInSavepointLevel"=-1) |
| 101 | |
| 102 | When you declare a temp table, it will have "declared in savepoint level" as the current savepoint |
| 103 | level of the LanguageConnectionContext (which will be 0 in a transaction with no user-defined savepoints). |
| 104 | The "dropped in savepoint level" for new temp tables will be set to -1. |
| 105 | The "dataModifiedInSavepointLevel" for new temp tables will be set to -1 as well. |
| 106 | |
| 107 | When a temp table is dropped, we will first check if the table was declared in a savepoint level |
| 108 | equal to the current savepoint level. |
| 109 | If yes, then we will remove it from the temp tables list for the LanguageConnectionContext . |
| 110 | eg |
| 111 | start tran ("current savepoint level = 0") |
| 112 | set savepoint 1("current savepoint level = 1") |
| 113 | declare temp table 1 ("declared in savepoint level"=1, "dropped in savepoint level"=-1) |
| 114 | drop temp table 1 (declared in savepoint level same as current savepoint level and hence will remove it from list of temp tables) |
| 115 | If no, then we will set the dropped in savepoint level as the current savepoint level of the |
| 116 | LanguageConnectionContext (which will be 0 in a transaction without savepoints and it also means |
| 117 | that the table was declared in a previous transaction). |
| 118 | |
| 119 | At the time of commit, go through all the temp tables with "dropped in savepoint level" != -1 (meaning dropped in this transaction) |
| 120 | and remove them from the temp tables list for the LanguageConnectionContext. All the rest of the temp tables with |
| 121 | "dropped in savepoint level" = -1, we will set their "declared in savepoint level" to -1 and , "dataModifiedInSavepointLevel" to -1. |
| 122 | eg |
| 123 | start tran ("current savepoint level = 0) |
| 124 | declare temp table t1("declared in savepoint level" = 0, "dropped in savepoint level"=-1) |
| 125 | commit (temp table 1 ("declared in savepoint level"=-1, "dropped in savepoint level"=-1)) |
| 126 | start tran ("current savepoint level = 0) |
| 127 | drop temp table t1 ("declared in savepoint level" = -1, "dropped in savepoint level"=0) |
| 128 | commit (temp table t1 will be removed from list of temp tables) |
| 129 | |
| 130 | At the time of rollback |
| 131 | if rolling back transaction, first set the "current savepoint level" to 0 |
| 132 | if rolling back to a savepoint, first set the "current savepoint level" to savepoint level returned by Store |
| 133 | for the rollback to savepoint command |
| 134 | Now go through all the temp tables. |
| 135 | If "declared in savepoint level" of temp table is greater than or equal to "current savepoint level" |
| 136 | (ie table was declared in this unit of work) |
| 137 | And if table was not dropped in this unit of work ie "dropped in savepoint level" = -1 |
| 138 | Then we should remove the table from the list of temp tables and drop the conglomerate created for it |
| 139 | eg |
| 140 | start tran ("current savepoint level = 0) |
| 141 | declare temp table t2("declared in savepoint level" = 0, "dropped in savepoint level"=-1) |
| 142 | rollback tran |
| 143 | (temp table t2 will be removed from list of tables and conglomerate associated with it will be dropped) |
| 144 | And if table was dropped in this unit of work ie "dropped in savepoint level" >= "current savepoint level" |
| 145 | Then we should remove the table from the list of temp tables |
| 146 | eg |
| 147 | start tran ("current savepoint level = 0) |
| 148 | set savepoint 1("current savepoint level = 1") |
| 149 | declare temp table t2("declared in savepoint level" = 1, "dropped in savepoint level"=-1) |
| 150 | set savepoint 2("current savepoint level = 2") |
| 151 | drop temp table t1 ("declared in savepoint level" = 1, "dropped in savepoint level"=2) |
| 152 | rollback savepoint 1 ("current savepoint level = 0) temp table t1 will be removed from the list of temp tables |
| 153 | Else if the "dropped in savepoint level" of temp table is greate than or equal to "current savepoint level" |
| 154 | it mean that table was dropped in this unit of work (and was declared in an earlier savepoint unit / transaction) and we will |
| 155 | restore it as part of rollback ie replace the existing entry for this table in valid temp tables list with restored temp table. |
| 156 | At the end of restoring, "declared in savepoint level" will remain unchanged and "dropped in savepoint level" will be -1. |
| 157 | eg |
| 158 | start tran ("current savepoint level = 0) |
| 159 | declare temp table t1 with definition 1("declared in savepoint level" = 0, "dropped in savepoint level"=-1, definition 1(stored in table descriptor)) |
| 160 | commit (temp table t1 "declared in savepoint level" = -1, "dropped in savepoint level"=-1) |
| 161 | start tran ("current savepoint level = 0) |
| 162 | set savepoint 1("current savepoint level = 1") |
| 163 | drop temp table t1 ("declared in savepoint level" = -1, "dropped in savepoint level"=1, definition 1(stored in table descriptor)) |
| 164 | declare temp table t1 with definition 2(say different than definition 1) |
| 165 | ("declared in savepoint level" = -1, "dropped in savepoint level"=1, definition 1(stored in table descriptor)) , |
| 166 | ("declared in savepoint level" = 1, "dropped in savepoint level"=-1, definition 2(stored in table descriptor)) |
| 167 | set savepoint 2("current savepoint level = 2") |
| 168 | drop temp table t1("declared in savepoint level" = -1, "dropped in savepoint level"=1, definition 1(stored in table descriptor)) , |
| 169 | ("declared in savepoint level" = 1, "dropped in savepoint level"=2, definition 2(stored in table descriptor)) |
| 170 | rollback tran |
| 171 | (Remove : temp table t1("declared in savepoint level" = 1, "dropped in savepoint level"=2, definition 2(stored in table descriptor) |
| 172 | (Restore : temp table t1"declared in savepoint level" = -1, "dropped in savepoint level"=-1, definition 1(stored in table descriptor)) |
| 173 | Else if the "dataModifiedInSavepointLevel" of temp table is greate than or equal to "current savepoint level" |
| 174 | it means that table was declared in an earlier savepoint unit / transaction and was modified in the current UOW. And hence we will delete all the |
| 175 | data from it. |
| 176 | */ |
| 177 | class TempTableInfo |
| 178 | { |
| 179 | |
| 180 | private TableDescriptor td; |
| 181 | private int declaredInSavepointLevel; |
| 182 | private int droppededInSavepointLevel; |
| 183 | private int dataModifiedInSavepointLevel; |
| 184 | |
| 185 | TempTableInfo(TableDescriptor td, int declaredInSavepointLevel) |
| 186 | { |
| 187 | this.td = td; |
| 188 | this.declaredInSavepointLevel = declaredInSavepointLevel; |
| 189 | this.droppededInSavepointLevel = -1; |
| 190 | this.dataModifiedInSavepointLevel = -1; |
| 191 | } |
| 192 | |
| 193 | /** |
| 194 | * Return the table descriptor |
| 195 | */ |
| 196 | TableDescriptor getTableDescriptor() { |
| 197 | return td; |
| 198 | } |
| 199 | |
| 200 | /** |
| 201 | * Set the table descriptor. Will be called while temporary is being restored |
| 202 | */ |
| 203 | void setTableDescriptor(TableDescriptor td) { |
| 204 | this.td = td; |
| 205 | } |
| 206 | |
| 207 | /** |
| 208 | * Matches by name and only temp tables that have not been dropped (that's when droppededInSavepointLevel will be -1) |
| 209 | */ |
| 210 | boolean matches(String tableName) { |
| 211 | return (td.getName().equals(tableName) && droppededInSavepointLevel == -1); |
| 212 | } |
| 213 | |
| 214 | /** |
| 215 | * Return the savepoint level when the table was last modified |
| 216 | */ |
| 217 | int getModifiedInSavepointLevel() { |
| 218 | return dataModifiedInSavepointLevel; |
| 219 | } |
| 220 | |
| 221 | /** |
| 222 | * Set the savepoint level when the table was last modified |
| 223 | */ |
| 224 | void setModifiedInSavepointLevel(int dataModifiedInSavepointLevel) { |
| 225 | this.dataModifiedInSavepointLevel = dataModifiedInSavepointLevel; |
| 226 | } |
| 227 | |
| 228 | /** |
| 229 | * Return the savepoint level when the table was declared |
| 230 | */ |
| 231 | int getDeclaredInSavepointLevel() { |
| 232 | return declaredInSavepointLevel; |
| 233 | } |
| 234 | |
| 235 | /** |
| 236 | * Set the savepoint level when the table was declared |
| 237 | */ |
| 238 | void setDeclaredInSavepointLevel(int declaredInSavepointLevel) { |
| 239 | this.declaredInSavepointLevel = declaredInSavepointLevel; |
| 240 | } |
| 241 | |
| 242 | /** |
| 243 | * Return the savepoint level when the table was dropped |
| 244 | */ |
| 245 | int getDroppedInSavepointLevel() { |
| 246 | return droppededInSavepointLevel; |
| 247 | } |
| 248 | |
| 249 | /** |
| 250 | * Return the savepoint level when the table was dropped |
| 251 | */ |
| 252 | public void setDroppedInSavepointLevel(int droppededInSavepointLevel) { |
| 253 | this.droppededInSavepointLevel = droppededInSavepointLevel; |
| 254 | } |
| 255 | } |