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| <div class="subTitle"><span class="packageLabelInType">Package</span> <a href="package-summary.html">org.apache.calcite.linq4j.function</a></div> |
| <h1 title="Annotation Type Parameter" class="title">Annotation Type Parameter</h1> |
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| <section class="description"> |
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| <pre><a href="https://docs.oracle.com/javase/9/docs/api/java/lang/annotation/Retention.html?is-external=true" title="class or interface in java.lang.annotation" class="externalLink">@Retention</a>(<a href="https://docs.oracle.com/javase/9/docs/api/java/lang/annotation/RetentionPolicy.html?is-external=true#RUNTIME" title="class or interface in java.lang.annotation" class="externalLink">RUNTIME</a>) |
| <a href="https://docs.oracle.com/javase/9/docs/api/java/lang/annotation/Target.html?is-external=true" title="class or interface in java.lang.annotation" class="externalLink">@Target</a>(<a href="https://docs.oracle.com/javase/9/docs/api/java/lang/annotation/ElementType.html?is-external=true#PARAMETER" title="class or interface in java.lang.annotation" class="externalLink">PARAMETER</a>) |
| public @interface <span class="memberNameLabel">Parameter</span></pre> |
| <div class="block">Annotation that supplies metadata about a function parameter. |
| |
| <p>A typical use is to derive names for the parameters of user-defined |
| functions. |
| |
| <p>Here is an example: |
| |
| <blockquote><pre> |
| public static class MyLeftFunction { |
| public String eval( |
| @Parameter(name = "s") String s, |
| @Parameter(name = "n", optional = true) Integer n) { |
| return s.substring(0, n == null ? 1 : n); |
| } |
| }</pre></blockquote> |
| |
| <p>The first parameter is named "s" and is mandatory, |
| and the second parameter is named "n" and is optional. |
| |
| <p>If this annotation is present, it supersedes information that might be |
| available via |
| <code>Executable.getParameters()</code> (JDK 1.8 and above). |
| |
| <p>If the annotation is not specified, parameters will be named "arg0", |
| "arg1" et cetera, and will be mandatory.</div> |
| </section> |
| <section class="summary"> |
| <ul class="blockList"> |
| <!-- =========== ANNOTATION TYPE REQUIRED MEMBER SUMMARY =========== --> |
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| <section class="memberSummary"><a id="annotation.type.required.element.summary"> |
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| </a> |
| <h2>Required Element Summary</h2> |
| <div class="memberSummary"> |
| <table> |
| <caption><span>Required Elements</span><span class="tabEnd"> </span></caption> |
| <thead> |
| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colSecond" scope="col">Required Element</th> |
| <th class="colLast" scope="col">Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr class="altColor"> |
| <td class="colFirst"><code><a href="https://docs.oracle.com/javase/9/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang" class="externalLink">String</a></code></td> |
| <th class="colSecond" scope="row"><code><span class="memberNameLink"><a href="#name()">name</a></span></code></th> |
| <td class="colLast"> |
| <div class="block">The name of the parameter.</div> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </section> |
| </li> |
| <!-- =========== ANNOTATION TYPE OPTIONAL MEMBER SUMMARY =========== --> |
| <li class="blockList"> |
| <section class="memberSummary"><a id="annotation.type.optional.element.summary"> |
| <!-- --> |
| </a> |
| <h2>Optional Element Summary</h2> |
| <div class="memberSummary"> |
| <table> |
| <caption><span>Optional Elements</span><span class="tabEnd"> </span></caption> |
| <thead> |
| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colSecond" scope="col">Optional Element</th> |
| <th class="colLast" scope="col">Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr class="altColor"> |
| <td class="colFirst"><code>boolean</code></td> |
| <th class="colSecond" scope="row"><code><span class="memberNameLink"><a href="#optional()">optional</a></span></code></th> |
| <td class="colLast"> |
| <div class="block">Returns whether the parameter is optional.</div> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </section> |
| </li> |
| </ul> |
| </section> |
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| <!-- ============ ANNOTATION TYPE MEMBER DETAIL =========== --> |
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| <h2>Element Details</h2> |
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| <section class="detail"> |
| <h3><a id="name()">name</a></h3> |
| <div class="memberSignature"><span class="returnType"><a href="https://docs.oracle.com/javase/9/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang" class="externalLink">String</a></span> <span class="memberName">name</span></div> |
| <div class="block">The name of the parameter. |
| |
| <p>The name is used when the function is called |
| with parameter assignment, for example <code>foo(x => 1, y => 'a')</code>.</div> |
| </section> |
| </li> |
| </ul> |
| </section> |
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| <h3><a id="optional()">optional</a></h3> |
| <div class="memberSignature"><span class="returnType">boolean</span> <span class="memberName">optional</span></div> |
| <div class="block">Returns whether the parameter is optional. |
| |
| <p>An optional parameter does not need to be specified when you call the |
| function. |
| |
| <p>If you call a function using positional parameter syntax, you can omit |
| optional parameters on the trailing edge. For example, if you have a |
| function |
| <code>baz(int a, int b optional, int c, int d optional, int e optional)</code> |
| then you can call <code>baz(a, b, c, d, e)</code> |
| or <code>baz(a, b, c, d)</code> |
| or <code>baz(a, b, c)</code> |
| but not <code>baz(a, b)</code> because <code>c</code> is not optional. |
| |
| <p>If you call a function using parameter name assignment syntax, you can |
| omit any parameter that has a default value. For example, you can call |
| <code>baz(a => 1, e => 5, c => 3)</code>, omitting optional parameters <code>b</code> |
| and <code>d</code>. |
| |
| <p>Currently, the default value used when a parameter is not specified |
| is NULL, and therefore optional parameters must be nullable.</div> |
| <dl> |
| <dt>Default:</dt> |
| <dd>false</dd> |
| </dl> |
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