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| <div class="refsect1"> |
| <h2 class="refsect1"><font face="arial, helvetica, sans-serif" color="#330099">@CacheIndex</font></h2> |
| <p>Use <code>@CacheIndex</code> to define a cached index. Cache indexes are used only when caching is enabled.</p> |
| <a id="sthref34" name="sthref34"></a> |
| <p><strong><br /><span class="refsubsect">Annotation Elements</span></strong></p> |
| <p><a href="#BABFJHIC">Table 2-5</a> describes this annotation's elements.</p> |
| <div class="tblhruleformalwide"><a id="TLJPA341" name="TLJPA341"></a><a id="sthref35" name="sthref35"></a><a id="BABFJHIC" name="BABFJHIC"></a> |
| <p><strong><em><font face="arial, helvetica, sans-serif">Table 2-5 @CacheIndex Annotation Elements</font></em></strong></p> |
| <table class="HRuleFormalWide" title="@CacheIndex Annotation Elements" summary="This table describes the list of attributes for this annotation." dir="ltr" border="1" width="100%" frame="hsides" rules="rows" cellpadding="3" cellspacing="0"> |
| <col width="21%" /> |
| <col width="*" /> |
| <col width="20%" /> |
| <thead> |
| <tr align="left" valign="top"> |
| <th align="left" valign="bottom" id="r1c1-t9"><font face="Arial, Helvetica, sans-serif"><strong>Annotation Element</strong></font></th> |
| <th align="left" valign="bottom" id="r1c2-t9"><font face="Arial, Helvetica, sans-serif"><strong>Description</strong></font></th> |
| <th align="left" valign="bottom" id="r1c3-t9"><font face="Arial, Helvetica, sans-serif"><strong>Default</strong></font></th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr align="left" valign="top"> |
| <td align="left" id="r2c1-t9" headers="r1c1-t9"> |
| <p><code>columnNames</code></p> |
| </td> |
| <td align="left" headers="r2c1-t9 r1c2-t9"> |
| <p>(Optional) The set of columns on which to define the index. Not required when annotated on a field/method.</p> |
| </td> |
| <td align="left" headers="r2c1-t9 r1c3-t9"><br /></td> |
| </tr> |
| <tr align="left" valign="top"> |
| <td align="left" id="r3c1-t9" headers="r1c1-t9"> |
| <p><code>updateable</code></p> |
| </td> |
| <td align="left" headers="r3c1-t9 r1c2-t9"> |
| <p>(Optional) Specify if the indexed field is updateable.</p> |
| <p>If <code>true</code>, the object will be re-indexed on each update or refresh.</p> |
| </td> |
| <td align="left" headers="r3c1-t9 r1c3-t9"> |
| <p>true</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| <br /></div> |
| <!-- class="tblhruleformalwide" --> |
| <a id="sthref36" name="sthref36"></a> |
| <p><strong><br /><span class="refsubsect">Usage</span></strong></p> |
| <p>A cache index allows <code>singleResult</code> queries to obtain a cache hit when querying on the indexed fields. A <code>resultList</code> query cannot obtain cache hits, as it is unknown if all of the objects are in memory, (unless the cache usage query hint is used).</p> |
| <p>The index should be unique. If it is not, the first indexed object will be returned.</p> |
| <p>You can use <code>@CacheIndex</code> on an Entity class or on an attribute. The column is defaulted when defined on a attribute.</p> |
| <a id="sthref37" name="sthref37"></a> |
| <p><strong><br /><span class="refsubsect">Examples</span></strong></p> |
| <p><a href="#BABEECHH">Example 2-13</a> shows an example of using the <code>@CacheIndex</code> annotation.</p> |
| <div class="example"><a id="BABEECHH" name="BABEECHH"></a><a id="TLJPA342" name="TLJPA342"></a> |
| <p><strong><em><font face="arial, helvetica, sans-serif">Example 2-13 Using @CacheIndex Annotation</font></em></strong></p> |
| <pre xml:space="preserve" class="oac_no_warn"> |
| @Entity |
| <strong>@CacheIndex(columnNames={"F_NAME", "L_NAME"}, updateable=true)</strong> |
| public class Employee { |
| @Id |
| private long id; |
| @CacheIndex |
| private String ssn; |
| @Column(name="F_NAME") |
| private String firstName; |
| @Column(name="L_NAME") |
| private String lastName; |
| } |
| </pre></div> |
| <!-- class="example" --> |
| <p><a href="#BABIHBCC">Example 2-14</a> shows an example of using the <code><cache-index></code> XML element in the <code>eclipselink-orm.xml</code> file.</p> |
| <div class="example"><a id="BABIHBCC" name="BABIHBCC"></a><a id="TLJPA343" name="TLJPA343"></a> |
| <p><strong><em><font face="arial, helvetica, sans-serif">Example 2-14 Using <cache-index> XML</font></em></strong></p> |
| <pre xml:space="preserve" class="oac_no_warn"> |
| <?xml version="1.0"?> |
| <entity-mappings |
| xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/orm" |
| xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" |
| xsi:schemaLocation="http://www.eclipse.org/eclipselink/xsds/persistence/orm http://www.eclipse.org/eclipselink/xsds/eclipselink_orm_2_4.xsd" |
| version="2.4"> |
| <entity name="Employee" class="org.acme.Employee" access="FIELD"> |
| <strong><cache-index updateable="true"></strong> |
| <column-name>F_NAME</column-name> |
| <column-name>L_NAME</column-name> |
| <strong></cache-index></strong> |
| <attributes> |
| <id name="id"/> |
| <basic name="ssn"> |
| <cache-index/> |
| </basic> |
| <basic name="firstName"> |
| <column name="F_NAME"/> |
| </basic> |
| <basic name="lastName"> |
| <column name="L_NAME"/> |
| </basic> |
| </attributes> |
| </entity> |
| </entity-mappings> |
| </pre></div> |
| <!-- class="example" --> |
| <p><a href="#BABBIAGH">Example 2-15</a> shows an example query using a cache index.</p> |
| <div class="example"><a id="BABBIAGH" name="BABBIAGH"></a><a id="TLJPA344" name="TLJPA344"></a> |
| <p><strong><em><font face="arial, helvetica, sans-serif">Example 2-15 Caching an Index Query</font></em></strong></p> |
| <pre xml:space="preserve" class="oac_no_warn"> |
| Query query = em.createQuery("Select e from Employee e where e.firstName = :firstName and e.lastName = :lastName"); |
| query.setParameter("firstName", "Bob"); |
| query.setParameter("lastName", "Smith"); |
| Employee employee = (Employee)query.getSingleResult(); |
| </pre></div> |
| <!-- class="example" --> |
| <a id="sthref38" name="sthref38"></a> |
| <p><strong><br /><span class="refsubsect">See Also</span></strong></p> |
| <p>For more information, see:</p> |
| <ul> |
| <li> |
| <p><a href="a_cache.htm#CHDBBIHE">"@Cache"</a></p> |
| </li> |
| <li> |
| <p>"About Cache Indexes" in <em>Understanding EclipseLink</em></p> |
| </li> |
| </ul> |
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