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| <div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">org.apache.datafusion</a></div> |
| <h1 title="Interface ScalarFunction" class="title">Interface ScalarFunction</h1> |
| </div> |
| <section class="class-description" id="class-description"> |
| <hr> |
| <div class="type-signature"><span class="modifiers">public interface </span><span class="element-name type-name-label">ScalarFunction</span></div> |
| <div class="block">A Java-implemented scalar SQL function. Implementations declare their own name, signature, and |
| volatility, and evaluate one input batch at a time. |
| |
| <p>Mirrors DataFusion's <code>ScalarUDFImpl</code> trait. Wrap an instance in a <a href="ScalarUdf.html" title="class in org.apache.datafusion"><code>ScalarUdf</code></a> and |
| register it via <a href="SessionContext.html#registerUdf(org.apache.datafusion.ScalarUdf)"><code>SessionContext.registerUdf(ScalarUdf)</code></a> to make it callable from SQL or |
| DataFrame plans. |
| |
| <p>Implementations may be invoked concurrently by DataFusion on multiple worker threads. If the |
| implementation carries mutable state, the implementation must synchronize it.</div> |
| </section> |
| <section class="summary"> |
| <ul class="summary-list"> |
| <!-- ========== METHOD SUMMARY =========== --> |
| <li> |
| <section class="method-summary" id="method-summary"> |
| <h2>Method Summary</h2> |
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| <div class="table-header col-first">Modifier and Type</div> |
| <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-tab2 method-summary-table-tab3"><code><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/List.html" title="class or interface in java.util" class="external-link">List</a><org.apache.arrow.vector.types.pojo.Field></code></div> |
| <div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#argFields()" class="member-name-link">argFields</a>()</code></div> |
| <div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"> |
| <div class="block">Declared argument fields, in positional order.</div> |
| </div> |
| <div class="col-first odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="ColumnarValue.html" title="interface in org.apache.datafusion">ColumnarValue</a></code></div> |
| <div class="col-second odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#evaluate(org.apache.arrow.memory.BufferAllocator,org.apache.datafusion.ScalarFunctionArgs)" class="member-name-link">evaluate</a><wbr>(org.apache.arrow.memory.BufferAllocator allocator, |
| <a href="ScalarFunctionArgs.html" title="class in org.apache.datafusion">ScalarFunctionArgs</a> args)</code></div> |
| <div class="col-last odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"> |
| <div class="block">Compute the function result for one input batch.</div> |
| </div> |
| <div class="col-first even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link">String</a></code></div> |
| <div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#name()" class="member-name-link">name</a>()</code></div> |
| <div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"> |
| <div class="block">SQL name under which this function is invoked (e.g., <code>"add_one"</code>).</div> |
| </div> |
| <div class="col-first odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code>org.apache.arrow.vector.types.pojo.Field</code></div> |
| <div class="col-second odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#returnField()" class="member-name-link">returnField</a>()</code></div> |
| <div class="col-last odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"> |
| <div class="block">Declared return field.</div> |
| </div> |
| <div class="col-first even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="Volatility.html" title="enum class in org.apache.datafusion">Volatility</a></code></div> |
| <div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#volatility()" class="member-name-link">volatility</a>()</code></div> |
| <div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"> |
| <div class="block">Volatility classification.</div> |
| </div> |
| </div> |
| </div> |
| </div> |
| </section> |
| </li> |
| </ul> |
| </section> |
| <section class="details"> |
| <ul class="details-list"> |
| <!-- ============ METHOD DETAIL ========== --> |
| <li> |
| <section class="method-details" id="method-detail"> |
| <h2>Method Details</h2> |
| <ul class="member-list"> |
| <li> |
| <section class="detail" id="name()"> |
| <h3>name</h3> |
| <div class="member-signature"><span class="return-type"><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link">String</a></span> <span class="element-name">name</span>()</div> |
| <div class="block">SQL name under which this function is invoked (e.g., <code>"add_one"</code>).</div> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="argFields()"> |
| <h3>argFields</h3> |
| <div class="member-signature"><span class="return-type"><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/List.html" title="class or interface in java.util" class="external-link">List</a><org.apache.arrow.vector.types.pojo.Field></span> <span class="element-name">argFields</span>()</div> |
| <div class="block">Declared argument fields, in positional order. The function is registered with an exact |
| signature; calls whose argument types do not match exactly are rejected. |
| |
| <p>Each entry is an Arrow <code>Field</code> -- a name plus a <code>FieldType</code> plus an optional |
| list of child fields. Use <code>Field.nullable(String, org.apache.arrow.vector.types.pojo.ArrowType)</code> for primitive types (e.g. <code> |
| Field.nullable("arg0", new ArrowType.Int(32, true))</code>). Nested types like <code>List</code>, <code> |
| Struct</code>, and <code>Map</code> require the children list to carry element / member / key / value type |
| information; constructing a <code>Field</code> via <code>new Field(name, FieldType, children)</code> is |
| the canonical Arrow way to do that.</div> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="returnField()"> |
| <h3>returnField</h3> |
| <div class="member-signature"><span class="return-type">org.apache.arrow.vector.types.pojo.Field</span> <span class="element-name">returnField</span>()</div> |
| <div class="block">Declared return field. The returned <a href="ColumnarValue.html" title="interface in org.apache.datafusion"><code>ColumnarValue</code></a>'s vector must have this exact type, |
| including any nested children. Same construction rules as <a href="#argFields()"><code>argFields()</code></a>.</div> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="volatility()"> |
| <h3>volatility</h3> |
| <div class="member-signature"><span class="return-type"><a href="Volatility.html" title="enum class in org.apache.datafusion">Volatility</a></span> <span class="element-name">volatility</span>()</div> |
| <div class="block">Volatility classification. Use <a href="Volatility.html#IMMUTABLE"><code>Volatility.IMMUTABLE</code></a> for pure functions, <a href="Volatility.html#STABLE"><code>Volatility.STABLE</code></a> for functions deterministic within a query, and <a href="Volatility.html#VOLATILE"><code>Volatility.VOLATILE</code></a> |
| for non-deterministic functions.</div> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="evaluate(org.apache.arrow.memory.BufferAllocator,org.apache.datafusion.ScalarFunctionArgs)"> |
| <h3>evaluate</h3> |
| <div class="member-signature"><span class="return-type"><a href="ColumnarValue.html" title="interface in org.apache.datafusion">ColumnarValue</a></span> <span class="element-name">evaluate</span><wbr><span class="parameters">(org.apache.arrow.memory.BufferAllocator allocator, |
| <a href="ScalarFunctionArgs.html" title="class in org.apache.datafusion">ScalarFunctionArgs</a> args)</span></div> |
| <div class="block">Compute the function result for one input batch.</div> |
| <dl class="notes"> |
| <dt>Parameters:</dt> |
| <dd><code>allocator</code> - the <code>BufferAllocator</code> that MUST be used for any new Arrow vector |
| allocation, including the result. Buffers allocated from other allocators will not survive |
| the JNI handoff.</dd> |
| <dd><code>args</code> - the per-arg <a href="ColumnarValue.html" title="interface in org.apache.datafusion"><code>ColumnarValue</code></a>s and the batch row count. Each <a href="ColumnarValue.html" title="interface in org.apache.datafusion"><code>ColumnarValue</code></a> is a read-only view; the implementation must NOT close its underlying |
| vector.</dd> |
| <dt>Returns:</dt> |
| <dd>a <a href="ColumnarValue.html" title="interface in org.apache.datafusion"><code>ColumnarValue</code></a> of the declared return type. If <a href="ColumnarValue.Array.html" title="class in org.apache.datafusion"><code>ColumnarValue.Array</code></a>, |
| the underlying vector must have length <code>args.rowCount()</code>; if <a href="ColumnarValue.Scalar.html" title="class in org.apache.datafusion"><code>ColumnarValue.Scalar</code></a>, length 1. Ownership of the returned vector transfers to the |
| framework; the implementation must NOT close it.</dd> |
| </dl> |
| </section> |
| </li> |
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