GH-319: [Java] recipe to concatenate value vectors as one (#320)
Closes #319.
---------
Co-authored-by: David Li <li.davidm96@gmail.com>
diff --git a/java/source/conf.py b/java/source/conf.py
index fca55e1..5337b59 100644
--- a/java/source/conf.py
+++ b/java/source/conf.py
@@ -38,9 +38,9 @@
author = 'The Apache Software Foundation'
arrow_nightly=os.getenv("ARROW_NIGHTLY")
if arrow_nightly and arrow_nightly != '0':
- version = "13.0.0-SNAPSHOT"
+ version = "14.0.0-SNAPSHOT"
else:
- version = "12.0.0"
+ version = "13.0.0"
print(f"Running with Arrow version: {version}")
# -- General configuration ---------------------------------------------------
diff --git a/java/source/data.rst b/java/source/data.rst
index 04c7ce0..a8bc386 100644
--- a/java/source/data.rst
+++ b/java/source/data.rst
@@ -27,7 +27,7 @@
=============================
In some cases, VectorSchemaRoot needs to be modeled as a container. To accomplish
-this, you can use ``VectorSchemaRootAppender.append``. The following code
+this, you can use ``VectorSchemaRootAppender.append``. The following code
creates two roots, then concatenates them together:
.. testcode::
@@ -75,6 +75,46 @@
34
75
+Concatenate Value Vectors
+=========================
+
+In some cases, we need to concatenate two value vectors into one. To accomplish
+this, we can use `VectorAppender`_. This mutates the initial ValueVector.
+
+.. testcode::
+
+ import org.apache.arrow.memory.BufferAllocator;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.ValueVector;
+ import org.apache.arrow.vector.util.VectorAppender;
+
+ try (
+ BufferAllocator allocator = new RootAllocator();
+ IntVector initialValues = new IntVector("initialValues", allocator);
+ IntVector toAppend = new IntVector("toAppend", allocator);
+ ) {
+ initialValues.allocateNew(2);
+ initialValues.set(0, 1);
+ initialValues.set(1, 2);
+ initialValues.setValueCount(2);
+ System.out.println("Initial IntVector: " + initialValues);
+ toAppend.allocateNew(4);
+ toAppend.set(1, 4);
+ toAppend.set(3, 6);
+ toAppend.setValueCount(4);
+ System.out.println("IntVector to Append: " + toAppend);
+ VectorAppender appenderUtil = new VectorAppender(initialValues);
+ toAppend.accept(appenderUtil, null);
+ System.out.println("IntVector Result: " + initialValues);
+ }
+
+.. testoutput::
+
+ Initial IntVector: [1, 2]
+ IntVector to Append: [null, 4, null, 6]
+ IntVector Result: [1, 2, null, 4, null, 6]
+
Compare Vectors for Field Equality
==================================
@@ -331,3 +371,5 @@
.. testoutput::
[null, 8, 10]
+
+.. _`VectorAppender`: https://github.com/apache/arrow/blob/main/java/vector/src/main/java/org/apache/arrow/vector/util/VectorAppender.java
