1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<!--NewPage--> 3<HTML> 4<HEAD> 5<!-- Generated by javadoc (build 1.5.0) on Thu May 15 17:17:33 EDT 2008 --> 6<TITLE> 7com.sleepycat.persist.evolve (Oracle - Berkeley DB Java API) 8</TITLE> 9 10<META NAME="keywords" CONTENT="com.sleepycat.persist.evolve package"> 11 12<LINK REL ="stylesheet" TYPE="text/css" HREF="/style.css" TITLE="Style"> 13 14<SCRIPT type="text/javascript"> 15function windowTitle() 16{ 17 parent.document.title="com.sleepycat.persist.evolve (Oracle - Berkeley DB Java API)"; 18} 19</SCRIPT> 20<NOSCRIPT> 21</NOSCRIPT> 22 23</HEAD> 24 25<BODY BGCOLOR="white" onload="windowTitle();"> 26 27 28<!-- ========= START OF TOP NAVBAR ======= --> 29<A NAME="navbar_top"><!-- --></A> 30<A HREF="#skip-navbar_top" title="Skip navigation links"></A> 31<TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0" SUMMARY=""> 32<TR> 33<TD COLSPAN=2 BGCOLOR="#EEEEFF" 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67<NOSCRIPT> 68 <A HREF="/allclasses-noframe.html"><B>All Classes</B></A> 69</NOSCRIPT> 70 71 72</FONT></TD> 73</TR> 74</TABLE> 75<A NAME="skip-navbar_top"></A> 76<!-- ========= END OF TOP NAVBAR ========= --> 77 78<HR> 79<H2> 80Package com.sleepycat.persist.evolve 81</H2> 82Utilities for managing class evolution of persistent objects. 83<P> 84<B>See:</B> 85<BR> 86 <A HREF="#package_description"><B>Description</B></A> 87<P> 88 89<TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""> 90<TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"> 91<TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2"> 92<B>Interface Summary</B></FONT></TH> 93</TR> 94<TR BGCOLOR="white" CLASS="TableRowColor"> 95<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/Conversion.html" title="interface in com.sleepycat.persist.evolve">Conversion</A></B></TD> 96<TD>Converts an old version of an object value to conform to the current class 97 or field definition.</TD> 98</TR> 99<TR BGCOLOR="white" CLASS="TableRowColor"> 100<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/EvolveListener.html" title="interface in com.sleepycat.persist.evolve">EvolveListener</A></B></TD> 101<TD>The listener interface called during eager entity evolution.</TD> 102</TR> 103</TABLE> 104 105 106<P> 107 108<TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""> 109<TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"> 110<TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2"> 111<B>Class Summary</B></FONT></TH> 112</TR> 113<TR BGCOLOR="white" CLASS="TableRowColor"> 114<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/Converter.html" title="class in com.sleepycat.persist.evolve">Converter</A></B></TD> 115<TD>A mutation for converting an old version of an object value to conform to 116 the current class or field definition.</TD> 117</TR> 118<TR BGCOLOR="white" CLASS="TableRowColor"> 119<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/Deleter.html" title="class in com.sleepycat.persist.evolve">Deleter</A></B></TD> 120<TD>A mutation for deleting an entity class or field.</TD> 121</TR> 122<TR BGCOLOR="white" CLASS="TableRowColor"> 123<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/EntityConverter.html" title="class in com.sleepycat.persist.evolve">EntityConverter</A></B></TD> 124<TD>A subclass of Converter that allows specifying keys to be deleted.</TD> 125</TR> 126<TR BGCOLOR="white" CLASS="TableRowColor"> 127<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/EvolveConfig.html" title="class in com.sleepycat.persist.evolve">EvolveConfig</A></B></TD> 128<TD>Configuration properties for eager conversion of unevolved objects.</TD> 129</TR> 130<TR BGCOLOR="white" CLASS="TableRowColor"> 131<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/EvolveEvent.html" title="class in com.sleepycat.persist.evolve">EvolveEvent</A></B></TD> 132<TD>The event passed to the EvolveListener interface during eager entity 133 evolution.</TD> 134</TR> 135<TR BGCOLOR="white" CLASS="TableRowColor"> 136<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/EvolveInternal.html" title="class in com.sleepycat.persist.evolve">EvolveInternal</A></B></TD> 137<TD>Internal access class that should not be used by applications.</TD> 138</TR> 139<TR BGCOLOR="white" CLASS="TableRowColor"> 140<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/EvolveStats.html" title="class in com.sleepycat.persist.evolve">EvolveStats</A></B></TD> 141<TD>Statistics accumulated during eager entity evolution.</TD> 142</TR> 143<TR BGCOLOR="white" CLASS="TableRowColor"> 144<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/Mutation.html" title="class in com.sleepycat.persist.evolve">Mutation</A></B></TD> 145<TD>The base class for all mutations.</TD> 146</TR> 147<TR BGCOLOR="white" CLASS="TableRowColor"> 148<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/Mutations.html" title="class in com.sleepycat.persist.evolve">Mutations</A></B></TD> 149<TD>A collection of mutations for configuring class evolution.</TD> 150</TR> 151<TR BGCOLOR="white" CLASS="TableRowColor"> 152<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/Renamer.html" title="class in com.sleepycat.persist.evolve">Renamer</A></B></TD> 153<TD>A mutation for renaming a class or field without changing the instance or 154 field value.</TD> 155</TR> 156</TABLE> 157 158 159<P> 160 161<TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""> 162<TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"> 163<TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2"> 164<B>Exception Summary</B></FONT></TH> 165</TR> 166<TR BGCOLOR="white" CLASS="TableRowColor"> 167<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/DeletedClassException.html" title="class in com.sleepycat.persist.evolve">DeletedClassException</A></B></TD> 168<TD>While reading from an index, an instance of a deleted class version was 169 encountered.</TD> 170</TR> 171<TR BGCOLOR="white" CLASS="TableRowColor"> 172<TD WIDTH="15%"><B><A HREF="/com/sleepycat/persist/evolve/IncompatibleClassException.html" title="class in com.sleepycat.persist.evolve">IncompatibleClassException</A></B></TD> 173<TD>A class has been changed incompatibly and no mutation has been configured to 174 handle the change or a new class version number has not been assigned.</TD> 175</TR> 176</TABLE> 177 178 179<P> 180<A NAME="package_description"><!-- --></A><H2> 181Package com.sleepycat.persist.evolve Description 182</H2> 183 184<P> 185Utilities for managing class evolution of persistent objects. 186 187<h1>Class Evolution</h1> 188 189<p>For persistent data that is not short lived, changes to persistent classes 190are almost inevitable. Some changes are compatible with existing types, and 191data conversion for these changes is performed automatically and transparently. 192Other changes are not compatible with existing types. Mutations can be used to 193explicitly manage many types of incompatible changes.</p> 194 195<p>Not all incompatible class changes can be handled via mutations. For 196example, complex refactoring may require a transformation that manipulates 197multiple entity instances at once. Such changes are not possible with 198mutations but can be made by performing a <a href="#storeConversion">store 199conversion</a>.</p> 200 201<p>The different categories of type changes are described below.</p> 202 203<h2>Key Field Changes</h2> 204 205<p>Unlike entity data, key data is not versioned. Therefore, the physical key 206format for an index is fixed once the index has been opened, and the changes 207allowed for key fields are very limited. The only changes allowed for key 208fields are:</p> 209<ul> 210<li>The name of a key field may be changed, as long as this change is 211accompanied by a <A HREF="/com/sleepycat/persist/evolve/Renamer.html" title="class in com.sleepycat.persist.evolve"><CODE>Renamer</CODE></A> mutation.</li> 212<li>A primitive type may be changed to its corresponding primitive wrapper 213type. This is a compatible change.</li> 214<li>For primary key fields and fields of a composite key class, a primitive 215wrapper type may be changed to its corresponding primitive type. This is 216allowed because these key fields with reference types may never have null 217values. This is a compatible change.</li> 218</ul> 219 220<p>Any other changes to a key field are incompatible and may be made only by 221performing a <a href="#storeConversion">store conversion</a>.</p> 222 223<p>Key ordering, including the behavior of a custom <A HREF="http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Comparable.html" title="class or interface in java.lang"><CODE>Comparable</CODE></A>, is also fixed, since keys are stored in order in the 224index. The specifications for key ordering may not be changed, and the 225developer is responsible for not changing the behavior of a <code>Comparable</code> 226key class. <strong>WARNING:</strong>: Changing the behavior of a <code>Comparable</code> key class is likely to make the index unusable.</p> 227 228<h2>Compatible Type Changes</h2> 229 230<p>Entity data, unlike key data, is versioned. Therefore, some changes can be 231made compatibly and other changes can be handled via mutations. Compatible 232changes are defined below. To make a compatible class change, a mutation is 233not required; however, the class version must be assigned a new (greater) 234integer value.</p> 235 236<p>Changes to a class hierarchy are compatible in some cases. A new class may 237be inserted in the hierarchy. A class may be deleted from the hierarchy as 238long as one of the following is true: 1) it contains no persistent fields, 2) 239any persistent fields are deleted with field Deleter mutations, or 3) the class 240is deleted with a class Deleter mutation. Classes in an existing hierarchy may 241not be reordered compatibly, and fields may not moved from one class to another 242compatibly; for such changes a class Converter mutation is required.</p> 243 244<p>Changes to field types in entity class definitions are compatible when they 245conform to the Java Language Specification definitions for <a 246href="http://java.sun.com/docs/books/jls/third_edition/html/conversions.html#5.1.2">Widening 247Primitive Conversions</a> and <a 248href="http://java.sun.com/docs/books/jls/third_edition/html/conversions.html#5.1.5">Widening 249Reference Conversions</a>. For example, a smaller integer 250type may be changed to a larger integer type, and a reference type may be 251changed to one of its supertypes. Automatic widening conversions are performed 252as described in the Java Language Specification.</p> 253 254<p>Primitive types may also be compatibly changed to their corresponding 255primitive wrapper types, or to the wrapper type for a widened primitive type. 256However, changing from a primitive wrapper type to a primitive type is not a 257compatible change since existing null values could not be represented.</p> 258 259<p>Integer primitive types (byte, short, char, int, long) and their primitive 260wrapper types may be compatibly changed to the BigInteger type.</p> 261 262<p>In addition, adding fields to a class is a compatible change. When a 263persistent instance of a class is read that does not contain the new field, the 264new field is initialized by the default constructor.</p> 265 266<p>All other changes to instance fields are considered incompatible. 267Incompatible changes may be handled via mutations, as described next.</p> 268 269<p>Note that whenever a class is changed, either compatibly or incompatibly, a 270new (higher) class version number must be assigned. See <A HREF="/com/sleepycat/persist/model/Entity.html#version()"><CODE>Entity.version()</CODE></A> and <A HREF="/com/sleepycat/persist/model/Persistent.html#version()"><CODE>Persistent.version()</CODE></A> for information on assigning 271class version numbers.</p> 272 273<h2>Mutations</h2> 274 275<p>There are three types of mutations: <A HREF="/com/sleepycat/persist/evolve/Renamer.html" title="class in com.sleepycat.persist.evolve"><CODE>Renamer</CODE></A>, <A HREF="/com/sleepycat/persist/evolve/Deleter.html" title="class in com.sleepycat.persist.evolve"><CODE>Deleter</CODE></A> and <A HREF="/com/sleepycat/persist/evolve/Converter.html" title="class in com.sleepycat.persist.evolve"><CODE>Converter</CODE></A>.</p> 276 277<p>A class or field can be renamed using a <A HREF="/com/sleepycat/persist/evolve/Renamer.html" title="class in com.sleepycat.persist.evolve"><CODE>Renamer</CODE></A>. Renaming is not expensive, since it 278does not involve conversion of instance data.</p> 279 280<p>A class or field can be deleted using a <A HREF="/com/sleepycat/persist/evolve/Deleter.html" title="class in com.sleepycat.persist.evolve"><CODE>Deleter</CODE></A>.</p> 281<ul> 282<li>Deleting an entity class causes removal of the primary and secondary 283indices for the store, on other words, removal of all store entities for that 284class and its subclasses. Removal is performed when the store is opened. A 285<A HREF="/com/sleepycat/persist/evolve/Deleter.html" title="class in com.sleepycat.persist.evolve"><CODE>Deleter</CODE></A> should be used for an entity class 286in all of the following circumstances: 287 <ul> 288 <li>When removing the entity class itself.</li> 289 <li>When removing <A HREF="/com/sleepycat/persist/model/Entity.html" title="annotation in com.sleepycat.persist.model"><CODE>Entity</CODE></A> from the class 290 to make it non-persistent.</li> 291 <li>When removing <A HREF="/com/sleepycat/persist/model/Entity.html" title="annotation in com.sleepycat.persist.model"><CODE>Entity</CODE></A> from the class 292 and adding <A HREF="/com/sleepycat/persist/model/Persistent.html" title="annotation in com.sleepycat.persist.model"><CODE>Persistent</CODE></A>, to use it as an 293 embedded persistent class but not an entity class. The version of the class 294 must be incremented in this case.</li> 295 </ul> 296</li> 297 298<li>Deleting a non-entity class does not itself cause deletion of instance 299data, but is needed to inform DPL that the deleted class will not be used. 300Instances of the deleted class must be handled (discarded or converted to 301another class) by <A HREF="/com/sleepycat/persist/evolve/Deleter.html" title="class in com.sleepycat.persist.evolve"><CODE>Deleter</CODE></A> or <A HREF="/com/sleepycat/persist/evolve/Converter.html" title="class in com.sleepycat.persist.evolve"><CODE>Converter</CODE></A> mutations for the field or enclosing 302class that contain embedded instances of the deleted class. A <A HREF="/com/sleepycat/persist/evolve/Deleter.html" title="class in com.sleepycat.persist.evolve"><CODE>Deleter</CODE></A> should be used for a non-entity class in 303all of the following circumstances: 304 <ul> 305 <li>When removing the persistent class itself.</li> 306 <li>When removing <A HREF="/com/sleepycat/persist/model/Persistent.html" title="annotation in com.sleepycat.persist.model"><CODE>Persistent</CODE></A> from the 307 class to make it non-persistent.</li> 308 <li>When removing <A HREF="/com/sleepycat/persist/model/Persistent.html" title="annotation in com.sleepycat.persist.model"><CODE>Persistent</CODE></A> from the 309 class and adding <A HREF="/com/sleepycat/persist/model/Entity.html" title="annotation in com.sleepycat.persist.model"><CODE>Entity</CODE></A>, to use it as an 310 entity class but not an embedded persistent class. The version of the class 311 must be incremented in this case.</li> 312 </ul> 313</li> 314 315<li>Deleting a field causes automatic conversion of the instances containing 316that field, in order to discard the field values.</li> 317</ul> 318 319<p>Other incompatible changes are handled by creating a <A HREF="/com/sleepycat/persist/evolve/Converter.html" title="class in com.sleepycat.persist.evolve"><CODE>Converter</CODE></A> mutation and implementing a <A HREF="/com/sleepycat/persist/evolve/Conversion.html#convert(java.lang.Object)"><CODE>Conversion.convert</CODE></A> method that 320manipulates the raw objects and/or simple values directly. The <code>convert</code> 321method is passed an object of the old incompatible type and it returns an 322object of a current type.</p> 323 324<p>Conversions can be specified in two ways: for specific fields or for all 325instances of a class. A different <A HREF="/com/sleepycat/persist/evolve/Converter.html" title="class in com.sleepycat.persist.evolve"><CODE>Converter</CODE></A> constructor is used in each case. 326Field-specific conversions are used instead of class conversions when both are 327applicable.</p> 328 329<p>Note that each mutation is applied to a specific class version number. The 330class version must be explicitly specified in a mutation for two reasons:</p> 331<ol> 332<li>This provides safety in the face of multiple unconverted versions of a 333given type. Without a version, a single conversion method would have to handle 334multiple input types, and would have to distinguish between them by examining 335the data or type information.</li> 336<li>This allows arbitrary changes to be made. For example, a series of name 337changes may reuse a given name for more than one version. To identify the 338specific type being converted or renamed, a version number is needed.</li> 339</ol> 340<p>See <A HREF="/com/sleepycat/persist/model/Entity.html#version()"><CODE>Entity.version()</CODE></A> and <A HREF="/com/sleepycat/persist/model/Persistent.html#version()"><CODE>Persistent.version()</CODE></A> for information on assigning 341class version numbers.</p> 342 343<p>Mutations are therefore responsible for converting each existing 344incompatible class version to the current version as defined by a current class 345definition. For example, consider that class-version A-1 is initially changed 346to A-2 and a mutation is added for converting A-1 to A-2. If later changes in 347version A-3 occur before converting all A-1 instances to version A-2, the 348converter for A-1 will have to be changed. Instead of converting from A-1 to 349A-2 it will need to convert from A-1 to A-3. In addition, a mutation 350converting A-2 to A-3 will be needed.</p> 351 352<p>When a <A HREF="/com/sleepycat/persist/evolve/Converter.html" title="class in com.sleepycat.persist.evolve"><CODE>Converter</CODE></A> mutation applies to a 353given object, other mutations that may apply to that object are not 354automatically performed. It is the responsibility of the <A HREF="/com/sleepycat/persist/evolve/Converter.html" title="class in com.sleepycat.persist.evolve"><CODE>Converter</CODE></A> to return an object that conforms to 355the current class definition, including renaming fields and classes. If the 356input object has nested objects or superclasses that also need conversion, the 357converter must perform these nested conversions before returning the final 358converted object. This rule avoids the complexity and potential errors that 359could result if a converter mutation were automatically combined with other 360mutations in an arbitrary manner.</p> 361 362<p>The <A HREF="/com/sleepycat/persist/EntityStore.html#evolve(com.sleepycat.persist.evolve.EvolveConfig)"><CODE>EntityStore.evolve</CODE></A> 363method may optionally be used to ensure that all instances of an old class 364version are converted to the current version.</p> 365 366<h2>Other Metadata Changes</h2> 367 368<p>When a class that happens to be an entity class is renamed, it remains an 369entity class. When a field that happens to be a primary or 370secondary key field is renamed, its metadata remains intact as well.</p> 371 372<p>When the <A HREF="/com/sleepycat/persist/model/SecondaryKey.html" title="annotation in com.sleepycat.persist.model"><CODE>SecondaryKey</CODE></A> annotation is 373added to an <em>existing</em> field, a new index is created automatically. The 374new index will be populated by reading the entire primary index when the 375primary index is opened.</p> 376 377<p>When the <A HREF="/com/sleepycat/persist/model/SecondaryKey.html" title="annotation in com.sleepycat.persist.model"><CODE>SecondaryKey</CODE></A> annotation is 378included with a <em>new</em> field, a new index is created automatically. The 379new field is required to be a reference type (not a primitive) and must be 380initialized to null (the default behavior) in the default constructor. 381Entities will be indexed by the field when they are stored with a non-null key 382value.</p> 383 384<p>When a field with the <A HREF="/com/sleepycat/persist/model/SecondaryKey.html" title="annotation in com.sleepycat.persist.model"><CODE>SecondaryKey</CODE></A> 385annotation is deleted, or when the <A HREF="/com/sleepycat/persist/model/SecondaryKey.html" title="annotation in com.sleepycat.persist.model"><CODE>SecondaryKey</CODE></A> annotation is removed from a field 386without deleting it, the secondary index is removed (dropped). Removal occurs 387when the store is opened.</p> 388 389<p>The <A HREF="/com/sleepycat/persist/model/SecondaryKey.html#relate()"><CODE>SecondaryKey.relate</CODE></A> property may NOT be changed. All other properties of a 390<A HREF="/com/sleepycat/persist/model/SecondaryKey.html" title="annotation in com.sleepycat.persist.model"><CODE>SecondaryKey</CODE></A> may be changed, although 391avoiding changes that cause foreign key integrity errors is the responsibility 392of the application developer. For example, if the <A HREF="/com/sleepycat/persist/model/SecondaryKey.html#relatedEntity()"><CODE>SecondaryKey.relatedEntity()</CODE></A> property is added but 393not all existing secondary keys reference existing primary keys for the related 394entity, foreign key integrity errors may occur.</p> 395 396<p>The <A HREF="/com/sleepycat/persist/model/PrimaryKey.html" title="annotation in com.sleepycat.persist.model"><CODE>PrimaryKey</CODE></A> annotation may NOT be 397removed from a field in an entity class.</p> 398 399<p>The <A HREF="/com/sleepycat/persist/model/PrimaryKey.html#sequence()"><CODE>PrimaryKey.sequence()</CODE></A> property may be 400added, removed, or changed to a different name.</p> 401 402<p>The <A HREF="/com/sleepycat/persist/model/Persistent.html#proxyFor()"><CODE>Persistent.proxyFor()</CODE></A> property may be 403NOT be added, removed, or changed to a different class.</p> 404 405<h2>Warnings on Testing and Backups</h2> 406 407<p>The application developer is responsible for verifying that class evolution 408works properly before deploying with a changed set of persistent classes. The 409DPL will report errors when old class definitions cannot be evolved, for 410example, when a mutation is missing. To test that no such errors will occur, 411application test cases must include instances of all persistent classes.</p> 412 413<p>Converter mutations require special testing. Since the application 414conversion method is allowed to return instances of any type, the DPL cannot 415check that the proper type is returned until the data is accessed. To avoid 416data access errors, application test cases must cover converter mutations for 417all potential input and output types.</p> 418 419<p>When secondary keys are dropped or entity classes are deleted, the 420underlying databases are deleted and cannot be recovered from the store. This 421takes place when the store is opened. It is strongly recommended that a backup 422of the entire store is made before opening the store and causing class 423evolution to proceed.</p> 424 425<h2><a name="storeConversion">Store Conversion<a/></h2> 426 427<p>When mutations are not sufficient for handling class changes, a full store 428conversion may be performed. This is necessary for two particular types of 429class changes:</p> 430<ul> 431<li>A change to a physical key format, for example, a change from type 432<code>int</code> to type <code>long</code>.</li> 433<li>A conversion that involves multiple entities at once, for example, 434combining two separate entity classes into a new single entity class.</li> 435</ul> 436 437<p>To perform a full store conversion, a program is written that performs the 438following steps to copy the data from the old store to a new converted 439store:</p> 440<ol> 441<li>The old store is opened as a <A HREF="/com/sleepycat/persist/raw/RawStore.html" title="class in com.sleepycat.persist.raw"><CODE>RawStore</CODE></A> and 442the new store is opened as an <A HREF="/com/sleepycat/persist/EntityStore.html" title="class in com.sleepycat.persist"><CODE>EntityStore</CODE></A>.</li> 443<li>All entities are read from the old store. Entities are read using a <A HREF="/com/sleepycat/persist/raw/RawStore.html" title="class in com.sleepycat.persist.raw"><CODE>RawStore</CODE></A> to allow access to entities for which no 444compatible class exists.</li> 445<li>The <A HREF="/com/sleepycat/persist/raw/RawObject.html" title="class in com.sleepycat.persist.raw"><CODE>RawObject</CODE></A> entities are then converted 446to the format desired. Raw objects can be arbitrarily manipulated as needed. 447The updated raw objects must conform to the new evolved class definitions.</li> 448<li>The updated raw entities are converted to live objects by calling the 449<A HREF="/com/sleepycat/persist/model/EntityModel.html#convertRawObject(com.sleepycat.persist.raw.RawObject)"><CODE>EntityModel.convertRawObject</CODE></A> method of the new store. This method converts 450raw objects obtained from a different store, as long as they conform to the new 451evolved class definitions.</li> 452<li>The new live objects are written to the new <A HREF="/com/sleepycat/persist/EntityStore.html" title="class in com.sleepycat.persist"><CODE>EntityStore</CODE></A> using a <A HREF="/com/sleepycat/persist/PrimaryIndex.html" title="class in com.sleepycat.persist"><CODE>PrimaryIndex</CODE></A> as usual.</li> 453</ol> 454 455<p>To perform such a conversion, two separate stores must be open at once. 456Both stores may be in the same <A HREF="/com/sleepycat/db/Environment.html" title="class in com.sleepycat.db"><CODE>Environment</CODE></A>, if 457desired, by giving them different store names. But since all data is being 458rewritten, there are performance advantages to creating the new store in a new 459fresh environment: the data will be compacted as it is written, and the old 460store can be removed very quickly by deleting the old environment directory 461after the conversion is complete.</p> 462<P> 463 464<P> 465<DL> 466</DL> 467<HR> 468 469 470<!-- ======= START OF BOTTOM NAVBAR ====== --> 471<A NAME="navbar_bottom"><!-- --></A> 472<A HREF="#skip-navbar_bottom" title="Skip navigation links"></A> 473<TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0" SUMMARY=""> 474<TR> 475<TD COLSPAN=2 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> 476<A NAME="navbar_bottom_firstrow"><!-- --></A> 477<TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3" SUMMARY=""> 478 <TR ALIGN="center" VALIGN="top"> 479 <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="/overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> 480 <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Package</B></FONT> </TD> 481 <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <FONT CLASS="NavBarFont1">Class</FONT> </TD> 482 <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-use.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> 483 <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> 484 <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="/deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> 485 <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="/index-all.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> 486 <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="/help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> 487 </TR> 488</TABLE> 489</TD> 490<TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM> 491<b>Berkeley DB</b><br><font size="-1"> version 4.7.25</font></EM> 492</TD> 493</TR> 494 495<TR> 496<TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> 497 <A HREF="/com/sleepycat/persist/package-summary.html"><B>PREV PACKAGE</B></A> 498 <A HREF="/com/sleepycat/persist/model/package-summary.html"><B>NEXT PACKAGE</B></A></FONT></TD> 499<TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> 500 <A HREF="/index.html?com/sleepycat/persist/evolve/package-summary.html" target="_top"><B>FRAMES</B></A> 501 <A HREF="package-summary.html" target="_top"><B>NO FRAMES</B></A> 502 <SCRIPT type="text/javascript"> 503 <!-- 504 if(window==top) { 505 document.writeln('<A HREF="/allclasses-noframe.html"><B>All Classes</B></A>'); 506 } 507 //--> 508</SCRIPT> 509<NOSCRIPT> 510 <A HREF="/allclasses-noframe.html"><B>All Classes</B></A> 511</NOSCRIPT> 512 513 514</FONT></TD> 515</TR> 516</TABLE> 517<A NAME="skip-navbar_bottom"></A> 518<!-- ======== END OF BOTTOM NAVBAR ======= --> 519 520<HR> 521<font size=1>Copyright (c) 1996,2008 Oracle. 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