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| <section id="logical-plans-via-datafusion-proto"> |
| <h1>Logical plans via datafusion-proto<a class="headerlink" href="#logical-plans-via-datafusion-proto" title="Link to this heading">#</a></h1> |
| <p><code class="docutils literal notranslate"><span class="pre">SessionContext.fromProto(byte[])</span></code> accepts a serialized DataFusion |
| <code class="docutils literal notranslate"><span class="pre">LogicalPlanNode</span></code> and returns a lazy <code class="docutils literal notranslate"><span class="pre">DataFrame</span></code>. This is useful when you |
| already have a plan produced by another DataFusion-aware tool, or when |
| you want to construct the plan programmatically with finer-grained |
| control than the <code class="docutils literal notranslate"><span class="pre">sql</span></code> or DataFrame APIs.</p> |
| <p>The protobuf Java classes are generated by the build into the |
| <code class="docutils literal notranslate"><span class="pre">org.apache.datafusion.protobuf</span></code> (plan and expression nodes) and |
| <code class="docutils literal notranslate"><span class="pre">datafusion_common</span></code> (scalar values, schema, column references, file |
| formats) packages. The Maven build downloads pinned <code class="docutils literal notranslate"><span class="pre">.proto</span></code> files from |
| the matching upstream DataFusion tag on first build, then generates the |
| Java classes locally — see the |
| <a class="reference internal" href="../contributor-guide/updating-datafusion-version.html"><span class="std std-doc">Contributor Guide</span></a> |
| for how to bump the version.</p> |
| <section id="a-minimal-plan"> |
| <h2>A minimal plan<a class="headerlink" href="#a-minimal-plan" title="Link to this heading">#</a></h2> |
| <p>The smallest interesting plan is a projection of a literal over an |
| empty input. It is useful as a sanity check and exercises serialization |
| end-to-end without touching any storage.</p> |
| <div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.RootAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.IntVector</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.VectorSchemaRoot</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.ipc.ArrowReader</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.DataFrame</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.SessionContext</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.EmptyRelationNode</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.LogicalExprNode</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.LogicalPlanNode</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.ProjectionNode</span><span class="p">;</span> |
| |
| <span class="kn">import</span><span class="w"> </span><span class="nn">datafusion_common.DatafusionCommon</span><span class="p">;</span> |
| |
| <span class="n">LogicalPlanNode</span><span class="w"> </span><span class="n">plan</span><span class="w"> </span><span class="o">=</span> |
| <span class="w"> </span><span class="n">LogicalPlanNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setProjection</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">ProjectionNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setInput</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">LogicalPlanNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setEmptyRelation</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">EmptyRelationNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">().</span><span class="na">setProduceOneRow</span><span class="p">(</span><span class="kc">true</span><span class="p">).</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">addExpr</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">LogicalExprNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setLiteral</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">DatafusionCommon</span><span class="p">.</span><span class="na">ScalarValue</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">().</span><span class="na">setInt32Value</span><span class="p">(</span><span class="mi">1</span><span class="p">).</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">();</span> |
| |
| <span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="kd">var</span><span class="w"> </span><span class="n">allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RootAllocator</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">SessionContext</span><span class="w"> </span><span class="n">ctx</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SessionContext</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">DataFrame</span><span class="w"> </span><span class="n">df</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ctx</span><span class="p">.</span><span class="na">fromProto</span><span class="p">(</span><span class="n">plan</span><span class="p">.</span><span class="na">toByteArray</span><span class="p">());</span> |
| <span class="w"> </span><span class="n">ArrowReader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">df</span><span class="p">.</span><span class="na">collect</span><span class="p">(</span><span class="n">allocator</span><span class="p">))</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">loadNextBatch</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">VectorSchemaRoot</span><span class="w"> </span><span class="n">batch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">getVectorSchemaRoot</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">IntVector</span><span class="w"> </span><span class="n">col</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">IntVector</span><span class="p">)</span><span class="w"> </span><span class="n">batch</span><span class="p">.</span><span class="na">getVector</span><span class="p">(</span><span class="mi">0</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">col</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="mi">0</span><span class="p">));</span><span class="w"> </span><span class="c1">// 1</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <p><code class="docutils literal notranslate"><span class="pre">fromProto</span></code> performs the same logical-planning, optimization, and |
| physical-planning pipeline as <code class="docutils literal notranslate"><span class="pre">sql</span></code>; the result is a lazy |
| <a class="reference internal" href="dataframe.html"><span class="std std-doc"><code class="docutils literal notranslate"><span class="pre">DataFrame</span></code></span></a> that only executes when you pull results.</p> |
| </section> |
| <section id="scanning-a-parquet-file-via-listingtablescannode"> |
| <h2>Scanning a Parquet file via ListingTableScanNode<a class="headerlink" href="#scanning-a-parquet-file-via-listingtablescannode" title="Link to this heading">#</a></h2> |
| <p>A <code class="docutils literal notranslate"><span class="pre">ListingTableScanNode</span></code> reads one or more files of the same format |
| from disk. Unlike <code class="docutils literal notranslate"><span class="pre">registerParquet</span></code>, it does not require the table to |
| be in the catalog — the scan node carries everything DataFusion needs: |
| the file paths, the schema, the projection, the file format, and the |
| target partition count.</p> |
| <p>The scan node’s <code class="docutils literal notranslate"><span class="pre">schema</span></code> field is a <code class="docutils literal notranslate"><span class="pre">datafusion_common.Schema</span></code>, not an |
| Arrow <code class="docutils literal notranslate"><span class="pre">Schema</span></code>. Convert between the two with the helper in |
| <code class="docutils literal notranslate"><span class="pre">org.apache.datafusion.proto.SchemaConverter</span></code>:</p> |
| <div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Schema</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.proto.SchemaConverter</span><span class="p">;</span> |
| |
| <span class="n">Schema</span><span class="w"> </span><span class="n">arrow</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ctx</span><span class="p">.</span><span class="na">tableSchema</span><span class="p">(</span><span class="s">"lineitem"</span><span class="p">);</span> |
| <span class="n">DatafusionCommon</span><span class="p">.</span><span class="na">Schema</span><span class="w"> </span><span class="n">schemaProto</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">SchemaConverter</span><span class="p">.</span><span class="na">toProto</span><span class="p">(</span><span class="n">arrow</span><span class="p">);</span> |
| </pre></div> |
| </div> |
| <p>The full example: register the file once to introspect its schema, |
| then build a plan that scans the same file, sorts by <code class="docutils literal notranslate"><span class="pre">l_orderkey</span></code>, |
| and fetches the first row. This is equivalent to |
| <code class="docutils literal notranslate"><span class="pre">SELECT</span> <span class="pre">l_orderkey</span> <span class="pre">FROM</span> <span class="pre">lineitem</span> <span class="pre">ORDER</span> <span class="pre">BY</span> <span class="pre">l_orderkey</span> <span class="pre">LIMIT</span> <span class="pre">1</span></code>.</p> |
| <div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.BareTableReference</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.ListingTableScanNode</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.ProjectionColumns</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.SortExprNode</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.SortNode</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.protobuf.TableReference</span><span class="p">;</span> |
| |
| <span class="n">String</span><span class="w"> </span><span class="n">path</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"/path/to/lineitem.parquet"</span><span class="p">;</span> |
| |
| <span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="kd">var</span><span class="w"> </span><span class="n">allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RootAllocator</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">SessionContext</span><span class="w"> </span><span class="n">ctx</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SessionContext</span><span class="p">())</span><span class="w"> </span><span class="p">{</span> |
| |
| <span class="w"> </span><span class="n">ctx</span><span class="p">.</span><span class="na">registerParquet</span><span class="p">(</span><span class="s">"lineitem"</span><span class="p">,</span><span class="w"> </span><span class="n">path</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">DatafusionCommon</span><span class="p">.</span><span class="na">Schema</span><span class="w"> </span><span class="n">schemaProto</span><span class="w"> </span><span class="o">=</span> |
| <span class="w"> </span><span class="n">SchemaConverter</span><span class="p">.</span><span class="na">toProto</span><span class="p">(</span><span class="n">ctx</span><span class="p">.</span><span class="na">tableSchema</span><span class="p">(</span><span class="s">"lineitem"</span><span class="p">));</span> |
| |
| <span class="w"> </span><span class="n">LogicalExprNode</span><span class="w"> </span><span class="n">orderKeyCol</span><span class="w"> </span><span class="o">=</span> |
| <span class="w"> </span><span class="n">LogicalExprNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setColumn</span><span class="p">(</span><span class="n">DatafusionCommon</span><span class="p">.</span><span class="na">Column</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">().</span><span class="na">setName</span><span class="p">(</span><span class="s">"l_orderkey"</span><span class="p">).</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">();</span> |
| |
| <span class="w"> </span><span class="n">LogicalPlanNode</span><span class="w"> </span><span class="n">plan</span><span class="w"> </span><span class="o">=</span> |
| <span class="w"> </span><span class="n">LogicalPlanNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setSort</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">SortNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setInput</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">LogicalPlanNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setListingScan</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">ListingTableScanNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setTableName</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">TableReference</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setBare</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">BareTableReference</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setTable</span><span class="p">(</span><span class="s">"lineitem"</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">addPaths</span><span class="p">(</span><span class="n">path</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setFileExtension</span><span class="p">(</span><span class="s">".parquet"</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setSchema</span><span class="p">(</span><span class="n">schemaProto</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setProjection</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">ProjectionColumns</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">addColumns</span><span class="p">(</span><span class="s">"l_orderkey"</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setParquet</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">DatafusionCommon</span><span class="p">.</span><span class="na">ParquetFormat</span><span class="p">.</span><span class="na">getDefaultInstance</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setTargetPartitions</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">addExpr</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">SortExprNode</span><span class="p">.</span><span class="na">newBuilder</span><span class="p">()</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setExpr</span><span class="p">(</span><span class="n">orderKeyCol</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setAsc</span><span class="p">(</span><span class="kc">true</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setNullsFirst</span><span class="p">(</span><span class="kc">false</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">setFetch</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">())</span> |
| <span class="w"> </span><span class="p">.</span><span class="na">build</span><span class="p">();</span> |
| |
| <span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">DataFrame</span><span class="w"> </span><span class="n">df</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ctx</span><span class="p">.</span><span class="na">fromProto</span><span class="p">(</span><span class="n">plan</span><span class="p">.</span><span class="na">toByteArray</span><span class="p">());</span> |
| <span class="w"> </span><span class="n">ArrowReader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">df</span><span class="p">.</span><span class="na">collect</span><span class="p">(</span><span class="n">allocator</span><span class="p">))</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">loadNextBatch</span><span class="p">();</span> |
| <span class="w"> </span><span class="c1">// ...</span> |
| <span class="w"> </span><span class="p">}</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| </section> |
| <section id="when-to-use-proto-plans"> |
| <h2>When to use proto plans<a class="headerlink" href="#when-to-use-proto-plans" title="Link to this heading">#</a></h2> |
| <p>The <code class="docutils literal notranslate"><span class="pre">sql</span></code> and DataFrame APIs are the right choice for most workloads. |
| Reach for <code class="docutils literal notranslate"><span class="pre">fromProto</span></code> when you need one of:</p> |
| <ul class="simple"> |
| <li><p><strong>Cross-tool interop.</strong> Accept plans produced by another |
| DataFusion-based system (a planner, a scheduler, a query frontend).</p></li> |
| <li><p><strong>Programmatic plan construction.</strong> Build the plan node tree directly |
| instead of going through SQL parsing, useful for tools that compile |
| their own surface language to DataFusion.</p></li> |
| <li><p><strong>Plan persistence.</strong> Serialize a plan to bytes, store or transmit |
| it, and execute it later — possibly in a different process or on a |
| different machine.</p></li> |
| </ul> |
| </section> |
| <section id="schema-conversion-support"> |
| <h2>Schema conversion support<a class="headerlink" href="#schema-conversion-support" title="Link to this heading">#</a></h2> |
| <p><code class="docutils literal notranslate"><span class="pre">SchemaConverter.toProto</span></code> and <code class="docutils literal notranslate"><span class="pre">SchemaConverter.fromProto</span></code> support the |
| primitive Arrow types this project’s tests exercise: <code class="docutils literal notranslate"><span class="pre">Bool</span></code>, signed and |
| unsigned integer types 8 through 64 bits, <code class="docutils literal notranslate"><span class="pre">Float32</span></code>, <code class="docutils literal notranslate"><span class="pre">Float64</span></code>, <code class="docutils literal notranslate"><span class="pre">Utf8</span></code>, |
| <code class="docutils literal notranslate"><span class="pre">Utf8View</span></code>, <code class="docutils literal notranslate"><span class="pre">LargeUtf8</span></code>, <code class="docutils literal notranslate"><span class="pre">Date32</span></code>, and <code class="docutils literal notranslate"><span class="pre">Decimal128</span></code>. Anything else |
| raises <code class="docutils literal notranslate"><span class="pre">UnsupportedOperationException</span></code> naming the offending type.</p> |
| </section> |
| </section> |
| |
| |
| </article> |
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