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<div class="sub-title"><span class="module-label-in-type">Module</span>&nbsp;<a href="../../../../../../module-summary.html">org.apache.jena.arq</a></div>
<div class="sub-title"><span class="package-label-in-type">Package</span>&nbsp;<a href="package-summary.html">org.apache.jena.sparql.algebra.optimize</a></div>
<h1 title="Class TransformImplicitLeftJoin" class="title">Class TransformImplicitLeftJoin</h1>
</div>
<div class="inheritance" title="Inheritance Tree"><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">java.lang.Object</a>
<div class="inheritance"><a href="../TransformCopy.html" title="class in org.apache.jena.sparql.algebra">org.apache.jena.sparql.algebra.TransformCopy</a>
<div class="inheritance">org.apache.jena.sparql.algebra.optimize.TransformImplicitLeftJoin</div>
</div>
</div>
<section class="class-description" id="class-description">
<dl class="notes">
<dt>All Implemented Interfaces:</dt>
<dd><code><a href="../Transform.html" title="interface in org.apache.jena.sparql.algebra">Transform</a></code></dd>
</dl>
<hr>
<div class="type-signature"><span class="modifiers">public class </span><span class="element-name type-name-label">TransformImplicitLeftJoin</span>
<span class="extends-implements">extends <a href="../TransformCopy.html" title="class in org.apache.jena.sparql.algebra">TransformCopy</a></span></div>
<div class="block"><p>
Optimizer for transforming implicit joins. These covers queries like the
following:
</p>
<pre>
SELECT *
WHERE
{
?s a ?type1 .
OPTIONAL
{
?t a ?type2 .
FILTER(?s = ?t)
}
}
</pre>
<p>
Clearly this is a trivial example but doing this optimization can have big
performance gains since it can completely eliminate cross products that we
would otherwise be required to evaluate. The optimization where applicable
results in a query of the following form:
</p>
<pre>
SELECT *
WHERE
{
?s a ?type1 .
OPTIONAL
{
?s a ?type1 .
BIND(?s AS ?t)
}
}
</pre>
<p>
This does not handle the simpler case of implicit joins where
<code>OPTIONAL</code> is not involved, for that see
<a href="TransformFilterImplicitJoin.html" title="class in org.apache.jena.sparql.algebra.optimize"><code>TransformFilterImplicitJoin</code></a>
</p>
<h3>Applicability</h3>
<p>
This optimization aims to eliminate implicit left joins of the form
<code>?x = ?y</code> or <code>SAMETERM(?x, ?y)</code>, the latter can almost always be
safely eliminated while the former may only be eliminated in the case where
we can guarantee that at least one of the variables is a non-literal e.g. it
occurs in the subject/predicate position. In the case where this is not true
the optimization may not be made since we cannot assume that we can map value
equality to term equality by making the optimization.
</p></div>
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<!-- =========== FIELD SUMMARY =========== -->
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<h2>Field Summary</h2>
<div class="inherited-list">
<h3 id="fields-inherited-from-class-org.apache.jena.sparql.algebra.TransformCopy">Fields inherited from class&nbsp;org.apache.jena.sparql.algebra.<a href="../TransformCopy.html" title="class in org.apache.jena.sparql.algebra">TransformCopy</a></h3>
<code><a href="../TransformCopy.html#COPY_ALWAYS">COPY_ALWAYS</a>, <a href="../TransformCopy.html#COPY_ONLY_ON_CHANGE">COPY_ONLY_ON_CHANGE</a></code></div>
</section>
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<!-- ======== CONSTRUCTOR SUMMARY ======== -->
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<h2>Constructor Summary</h2>
<div class="caption"><span>Constructors</span></div>
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<div class="table-header col-first">Constructor</div>
<div class="table-header col-last">Description</div>
<div class="col-constructor-name even-row-color"><code><a href="#%3Cinit%3E()" class="member-name-link">TransformImplicitLeftJoin</a>()</code></div>
<div class="col-last even-row-color">&nbsp;</div>
</div>
</section>
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<div class="col-first even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"><code><a href="../Op.html" title="interface in org.apache.jena.sparql.algebra">Op</a></code></div>
<div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"><code><a href="#transform(org.apache.jena.sparql.algebra.op.OpLeftJoin,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)" class="member-name-link">transform</a><wbr>(<a href="../op/OpLeftJoin.html" title="class in org.apache.jena.sparql.algebra.op">OpLeftJoin</a>&nbsp;opLeftJoin,
<a href="../Op.html" title="interface in org.apache.jena.sparql.algebra">Op</a>&nbsp;left,
<a href="../Op.html" title="interface in org.apache.jena.sparql.algebra">Op</a>&nbsp;right)</code></div>
<div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4">&nbsp;</div>
</div>
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<h3 id="methods-inherited-from-class-org.apache.jena.sparql.algebra.TransformCopy">Methods inherited from class&nbsp;org.apache.jena.sparql.algebra.<a href="../TransformCopy.html" title="class in org.apache.jena.sparql.algebra">TransformCopy</a></h3>
<code><a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpAssign,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpBGP)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpConditional,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpDatasetNames)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpDiff,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpDisjunction,java.util.List)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpDistinct,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpExt)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpExtend,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpFilter,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpGraph,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpGroup,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpJoin,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpLabel,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpLateral,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpList,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpMinus,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpNull)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpOrder,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpPath)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpProcedure,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpProject,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpPropFunc,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpQuad)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpQuadBlock)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpQuadPattern)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpReduced,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpSequence,java.util.List)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpService,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpSlice,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpTable)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpTopN,org.apache.jena.sparql.algebra.Op)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpTriple)">transform</a>, <a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpUnion,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">transform</a></code></div>
<div class="inherited-list">
<h3 id="methods-inherited-from-class-java.lang.Object">Methods inherited from class&nbsp;java.lang.<a href="https://docs.oracle.com/en/java/javase/17/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/17/docs/api/java.base/java/lang/Object.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/17/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/17/docs/api/java.base/java/lang/Object.html#hashCode()" title="class or interface in java.lang" class="external-link">hashCode</a>, <a href="https://docs.oracle.com/en/java/javase/17/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/17/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/17/docs/api/java.base/java/lang/Object.html#toString()" title="class or interface in java.lang" class="external-link">toString</a>, <a href="https://docs.oracle.com/en/java/javase/17/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/17/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/17/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">
<!-- ========= CONSTRUCTOR DETAIL ======== -->
<li>
<section class="constructor-details" id="constructor-detail">
<h2>Constructor Details</h2>
<ul class="member-list">
<li>
<section class="detail" id="&lt;init&gt;()">
<h3>TransformImplicitLeftJoin</h3>
<div class="member-signature"><span class="modifiers">public</span>&nbsp;<span class="element-name">TransformImplicitLeftJoin</span>()</div>
</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="transform(org.apache.jena.sparql.algebra.op.OpLeftJoin,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">
<h3>transform</h3>
<div class="member-signature"><span class="modifiers">public</span>&nbsp;<span class="return-type"><a href="../Op.html" title="interface in org.apache.jena.sparql.algebra">Op</a></span>&nbsp;<span class="element-name">transform</span><wbr><span class="parameters">(<a href="../op/OpLeftJoin.html" title="class in org.apache.jena.sparql.algebra.op">OpLeftJoin</a>&nbsp;opLeftJoin,
<a href="../Op.html" title="interface in org.apache.jena.sparql.algebra">Op</a>&nbsp;left,
<a href="../Op.html" title="interface in org.apache.jena.sparql.algebra">Op</a>&nbsp;right)</span></div>
<dl class="notes">
<dt>Specified by:</dt>
<dd><code><a href="../Transform.html#transform(org.apache.jena.sparql.algebra.op.OpLeftJoin,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">transform</a></code>&nbsp;in interface&nbsp;<code><a href="../Transform.html" title="interface in org.apache.jena.sparql.algebra">Transform</a></code></dd>
<dt>Overrides:</dt>
<dd><code><a href="../TransformCopy.html#transform(org.apache.jena.sparql.algebra.op.OpLeftJoin,org.apache.jena.sparql.algebra.Op,org.apache.jena.sparql.algebra.Op)">transform</a></code>&nbsp;in class&nbsp;<code><a href="../TransformCopy.html" title="class in org.apache.jena.sparql.algebra">TransformCopy</a></code></dd>
</dl>
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