apidocs/org/apache/calcite/linq4j/function/Parameter.html - calcite-site - Git at Google

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 <h2 title="Annotation Type Parameter" class="title">Annotation Type Parameter</h2>
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 <pre>@Retention(RUNTIME)
 @Target(PARAMETER)
 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(
        &#64;Parameter(name = "s") String s,
        &#64;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>
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 <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>
 <tr class="altColor">
 <td class="colFirst"><code>java.lang.String</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>
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 <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>
 <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>
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 <pre>java.lang.String&nbsp;name</pre>
 <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 =&gt; 1, y =&gt; 'a')</code>.</div>
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 <pre>boolean&nbsp;optional</pre>
 <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 =&gt; 1, e =&gt; 5, c =&gt; 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>
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	<div class="subTitle"><span class="packageLabelInType">Package</span> <a href="package-summary.html">org.apache.calcite.linq4j.function</a></div>
	<h2 title="Annotation Type Parameter" class="title">Annotation Type Parameter</h2>
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	<pre>@Retention(RUNTIME)
	@Target(PARAMETER)
	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>
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	<caption><span>Required Elements</span><span class="tabEnd"> </span></caption>
	<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>
	<tr class="altColor">
	<td class="colFirst"><code>java.lang.String</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>
	</table>
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	<!-- =========== ANNOTATION TYPE OPTIONAL MEMBER SUMMARY =========== -->
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	<h3>Optional Element Summary</h3>
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	<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>
	<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>
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	<h4>name</h4>
	<pre>java.lang.String name</pre>
	<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>
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	<pre>boolean optional</pre>
	<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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