org.apache.sis.storage/org/apache/sis/storage/FeatureQuery.ProjectionType.html - sis-site - Git at Google

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 <div class="sub-title"><span class="module-label-in-type">Module</span>&nbsp;<a href="../../../../module-summary.html">org.apache.sis.storage</a></div>
 <div class="sub-title"><span class="package-label-in-type">Package</span>&nbsp;<a href="package-summary.html">org.apache.sis.storage</a></div>
 <h1 title="Enum Class FeatureQuery.ProjectionType" class="title">Enum Class FeatureQuery.ProjectionType</h1>
 </div>
 <div class="inheritance" title="Inheritance Tree"><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a>
 <div class="inheritance"><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html" title="class or interface in java.lang" class="external-link">Enum</a>&lt;<a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a>&gt;
 <div class="inheritance">ProjectionType</div>
 </div>
 </div>
 <section class="class-description" id="class-description">
 <dl class="notes">
 <dt>All Implemented Interfaces:</dt>
 <dd><code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/Serializable.html" title="class or interface in java.io" class="external-link">Serializable</a></code>, <code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Comparable.html" title="class or interface in java.lang" class="external-link">Comparable</a>&lt;<a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a>&gt;</code>, <code>Constable</code></dd>
 </dl>
 <dl class="notes">
 <dt>Enclosing class:</dt>
 <dd><code><a href="FeatureQuery.html" title="class in org.apache.sis.storage">FeatureQuery</a></code></dd>
 </dl>
 <hr>
 <div class="type-signature"><span class="modifiers">public static enum </span><span class="element-name type-name-label">FeatureQuery.ProjectionType</span>
 <span class="extends-implements">extends <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html" title="class or interface in java.lang" class="external-link">Enum</a>&lt;<a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a>&gt;</span></div>
 <div class="block">Whether a property evaluated by a query is computed on the fly or stored.
  By default, an expression is evaluated only once for each feature instance,
  then the result is stored as a feature <a href="../../../../../org.apache.sis.feature/org/apache/sis/feature/AbstractAttribute.html" title="class in org.apache.sis.feature"><code>AbstractAttribute</code></a> value.
  But the same expression can also be wrapped in a feature <a href="../../../../../org.apache.sis.feature/org/apache/sis/feature/AbstractOperation.html" title="class in org.apache.sis.feature"><code>AbstractOperation</code></a>
  and evaluated every times that the value is requested.

  <h2 id="analogy-with-relational-databases-heading">Analogy with relational databases</h2>
  The terminology used in this enumeration is close to the one used in relational database.
  A <cite>projection</cite> is the set of feature properties to keep in the query results.
  The projection may contain <cite>generated columns</cite>, which are specified in SQL by
  <code>SQL GENERATED ALWAYS</code> statement, optionally with <code>STORED</code> or <code>VIRTUAL</code>
  modifier.</div>
 <dl class="notes">
 <dt>Since:</dt>
 <dd>1.4</dd>
 </dl>
 </section>
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 <!-- ======== NESTED CLASS SUMMARY ======== -->
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 <h2>Nested Class Summary</h2>
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 <h2 id="nested-classes-inherited-from-class-java.lang.Enum">Nested classes/interfaces inherited from class&nbsp;<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html" title="class or interface in java.lang" class="external-link">Enum</a></h2>
 <code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.EnumDesc.html" title="class or interface in java.lang" class="external-link">Enum.EnumDesc</a>&lt;<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.EnumDesc.html" title="class or interface in java.lang" class="external-link">E</a> extends <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html" title="class or interface in java.lang" class="external-link">Enum</a>&lt;<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.EnumDesc.html" title="class or interface in java.lang" class="external-link">E</a>&gt;&gt;</code></div>
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 <div class="caption"><span>Enum Constants</span></div>
 <div class="summary-table two-column-summary">
 <div class="table-header col-first">Enum Constant</div>
 <div class="table-header col-last">Description</div>
 <div class="col-first even-row-color"><code><a href="#COMPUTING" class="member-name-link">COMPUTING</a></code></div>
 <div class="col-last even-row-color">
 <div class="block">The expression is evaluated every times that the property value is requested.</div>
 </div>
 <div class="col-first odd-row-color"><code><a href="#STORED" class="member-name-link">STORED</a></code></div>
 <div class="col-last odd-row-color">
 <div class="block">The expression is evaluated exactly once when a feature instance is created,
  and the result is stored as a feature attribute.</div>
 </div>
 </div>
 </section>
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 <div class="table-header col-second">Method</div>
 <div class="table-header col-last">Description</div>
 <div class="col-first even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code>static <a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a></code></div>
 <div class="col-second even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code><a href="#valueOf(java.lang.String)" class="member-name-link">valueOf</a><wbr>(<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link">String</a>&nbsp;name)</code></div>
 <div class="col-last even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4">
 <div class="block">Returns the enum constant of this class with the specified name.</div>
 </div>
 <div class="col-first odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code>static <a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a>[]</code></div>
 <div class="col-second odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code><a href="#values()" class="member-name-link">values</a>()</code></div>
 <div class="col-last odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4">
 <div class="block">Returns an array containing the constants of this enum class, in
 the order they are declared.</div>
 </div>
 </div>
 </div>
 </div>
 <div class="inherited-list">
 <h3 id="methods-inherited-from-class-Enum">Methods inherited from class&nbsp;<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html" title="class or interface in java.lang" class="external-link">Enum</a></h3>
 <code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#clone()" title="class or interface in java.lang" class="external-link">clone</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#compareTo(E)" title="class or interface in java.lang" class="external-link">compareTo</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#describeConstable()" title="class or interface in java.lang" class="external-link">describeConstable</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#equals(java.lang.Object)" title="class or interface in java.lang" class="external-link">equals</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#finalize()" title="class or interface in java.lang" class="external-link">finalize</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#getDeclaringClass()" title="class or interface in java.lang" class="external-link">getDeclaringClass</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#hashCode()" title="class or interface in java.lang" class="external-link">hashCode</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#name()" title="class or interface in java.lang" class="external-link">name</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#ordinal()" title="class or interface in java.lang" class="external-link">ordinal</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#toString()" title="class or interface in java.lang" class="external-link">toString</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Enum.html#valueOf(java.lang.Class,java.lang.String)" title="class or interface in java.lang" class="external-link">valueOf</a></code></div>
 <div class="inherited-list">
 <h3 id="methods-inherited-from-class-Object">Methods inherited from class&nbsp;<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a></h3>
 <code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#getClass()" title="class or interface in java.lang" class="external-link">getClass</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#notify()" title="class or interface in java.lang" class="external-link">notify</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#notifyAll()" title="class or interface in java.lang" class="external-link">notifyAll</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#wait()" title="class or interface in java.lang" class="external-link">wait</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#wait(long)" title="class or interface in java.lang" class="external-link">wait</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#wait(long,int)" title="class or interface in java.lang" class="external-link">wait</a></code></div>
 </section>
 </li>
 </ul>
 </section>
 <section class="details">
 <ul class="details-list">
 <!-- ============ ENUM CONSTANT DETAIL =========== -->
 <li>
 <section class="constant-details" id="enum-constant-detail">
 <h2>Enum Constant Details</h2>
 <ul class="member-list">
 <li>
 <section class="detail" id="STORED">
 <h3>STORED</h3>
 <div class="member-signature"><span class="modifiers">public static final</span>&nbsp;<span class="return-type"><a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a></span>&nbsp;<span class="element-name">STORED</span></div>
 <div class="block">The expression is evaluated exactly once when a feature instance is created,
  and the result is stored as a feature attribute.
  The feature property type will be <a href="../../../../../org.apache.sis.feature/org/apache/sis/feature/AbstractAttribute.html" title="class in org.apache.sis.feature"><code>AbstractAttribute</code></a> and its value will be modifiable.
  This is the default projection type.

  <h4 id="feature-instances-in-expression-evaluation-heading">Feature instances in expression evaluation</h4>
  The features given in calls to <a href="../../../../../org.apache.sis.feature/org/apache/sis/filter/Expression.html#apply(R)"><code>Expression.apply(Object)</code></a> are instances from the
  <em>source</em> <a href="FeatureSet.html" title="interface in org.apache.sis.storage"><code>FeatureSet</code></a>, before filtering.</div>
 </section>
 </li>
 <li>
 <section class="detail" id="COMPUTING">
 <h3>COMPUTING</h3>
 <div class="member-signature"><span class="modifiers">public static final</span>&nbsp;<span class="return-type"><a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a></span>&nbsp;<span class="element-name">COMPUTING</span></div>
 <div class="block">The expression is evaluated every times that the property value is requested.
  The feature property type will be <a href="../../../../../org.apache.sis.feature/org/apache/sis/feature/AbstractOperation.html" title="class in org.apache.sis.feature"><code>AbstractOperation</code></a>.
  This projection type may be preferable to <a href="#STORED"><code>STORED</code></a> in the following circumstances:

  <ul>
    <li>The expression may produce different results every times that it is evaluated.</li>
    <li>The feature property should be a <a href="../../../../../org.apache.sis.feature/org/apache/sis/feature/FeatureOperations.html#link(java.util.Map,org.apache.sis.feature.AbstractIdentifiedType)">link</a> to another attribute.</li>
    <li>Potentially expensive computation should be deferred until first needed.</li>
    <li>Computation result should not be stored in order to reduce memory usage.</li>
  </ul>

  <h4 id="feature-instances-in-expression-evaluation-heading1">Feature instances in expression evaluation</h4>
  The features given in calls to <a href="../../../../../org.apache.sis.feature/org/apache/sis/filter/Expression.html#apply(R)"><code>Expression.apply(Object)</code></a> are instances from the <em>target</em>
  <a href="FeatureSet.html" title="interface in org.apache.sis.storage"><code>FeatureSet</code></a>, after filtering. The instances from the source <code>FeatureSet</code> are no longer
  available when the expression is executed. Consequently, all fields that are necessary for computing
  a <code>COMPUTING</code> field shall have been first copied in <a href="#STORED"><code>STORED</code></a> fields.

  <div class="note"><b>Note on naming:</b>
  verb tense <i>-ing</i> instead of <i>-ed</i> is for emphasizing that the data used for computation
  are current (filtered) data instead of past (original) data.</div></div>
 <dl class="notes">
 <dt>See Also:</dt>
 <dd>
 <ul class="tag-list-long">
 <li><a href="../../../../../org.apache.sis.feature/org/apache/sis/feature/FeatureOperations.html#function(java.util.Map,java.util.function.Function,org.apache.sis.feature.DefaultAttributeType)"><code>FeatureOperations.function(Map, Function, AttributeType)</code></a></li>
 </ul>
 </dd>
 </dl>
 </section>
 </li>
 </ul>
 </section>
 </li>
 <!-- ============ METHOD DETAIL ========== -->
 <li>
 <section class="method-details" id="method-detail">
 <h2>Method Details</h2>
 <ul class="member-list">
 <li>
 <section class="detail" id="values()">
 <h3>values</h3>
 <div class="member-signature"><span class="modifiers">public static</span>&nbsp;<span class="return-type"><a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a>[]</span>&nbsp;<span class="element-name">values</span>()</div>
 <div class="block">Returns an array containing the constants of this enum class, in
 the order they are declared.</div>
 <dl class="notes">
 <dt>Returns:</dt>
 <dd>an array containing the constants of this enum class, in the order they are declared</dd>
 </dl>
 </section>
 </li>
 <li>
 <section class="detail" id="valueOf(java.lang.String)">
 <h3>valueOf</h3>
 <div class="member-signature"><span class="modifiers">public static</span>&nbsp;<span class="return-type"><a href="FeatureQuery.ProjectionType.html" title="enum class in org.apache.sis.storage">FeatureQuery.ProjectionType</a></span>&nbsp;<span class="element-name">valueOf</span><wbr><span class="parameters">(<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link">String</a>&nbsp;name)</span></div>
 <div class="block">Returns the enum constant of this class with the specified name.
 The string must match <i>exactly</i> an identifier used to declare an
 enum constant in this class.  (Extraneous whitespace characters are
 not permitted.)</div>
 <dl class="notes">
 <dt>Parameters:</dt>
 <dd><code>name</code> - the name of the enum constant to be returned.</dd>
 <dt>Returns:</dt>
 <dd>the enum constant with the specified name</dd>
 <dt>Throws:</dt>
 <dd><code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/IllegalArgumentException.html" title="class or interface in java.lang" class="external-link">IllegalArgumentException</a></code> - if this enum class has no constant with the specified name</dd>
 <dd><code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/NullPointerException.html" title="class or interface in java.lang" class="external-link">NullPointerException</a></code> - if the argument is null</dd>
 </dl>
 </section>
 </li>
 </ul>
 </section>
 </li>
 </ul>
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