davisusanibar commented on a change in pull request #113:
URL: https://github.com/apache/arrow-cookbook/pull/113#discussion_r782258223
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File path: java/source/schema.rst
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@@ -0,0 +1,330 @@
+===================
+Working with schema
+===================
+
+Common definition of table has an schema. Java arrow is columnar oriented and
it also has an schema representation.
+Consider that each name on the schema maps to a columns for a predefined data
type
+
+
+.. contents::
+
+We are going to use this util for creating arrow objects:
+
+.. code-block:: java
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.BitVectorHelper;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.complex.BaseRepeatedValueVector;
+ import org.apache.arrow.vector.complex.ListVector;
+ import org.apache.arrow.vector.types.Types;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+
+ import java.util.List;
+
+
+ void setVector(IntVector vector, Integer... values) {
+ final int length = values.length;
+ vector.allocateNew(length);
+ for (int i = 0; i < length; i++) {
+ if (values[i] != null) {
+ vector.set(i, values[i]);
+ }
+ }
+ vector.setValueCount(length);
+ }
+
+ void setVector(VarCharVector vector, byte[]... values) {
+ final int length = values.length;
+ vector.allocateNewSafe();
+ for (int i = 0; i < length; i++) {
+ if (values[i] != null) {
+ vector.set(i, values[i]);
+ }
+ }
+ vector.setValueCount(length);
+ }
+
+ void setVector(ListVector vector, List<Integer>... values) {
+ vector.allocateNewSafe();
+ Types.MinorType type = Types.MinorType.INT;
+ vector.addOrGetVector(FieldType.nullable(type.getType()));
+
+ IntVector dataVector = (IntVector) vector.getDataVector();
+ dataVector.allocateNew();
+
+ // set underlying vectors
+ int curPos = 0;
+ vector.getOffsetBuffer().setInt(0, curPos);
+ for (int i = 0; i < values.length; i++) {
+ if (values[i] == null) {
+ BitVectorHelper.unsetBit(vector.getValidityBuffer(), i);
+ } else {
+ BitVectorHelper.setBit(vector.getValidityBuffer(), i);
+ for (int value : values[i]) {
+ dataVector.setSafe(curPos, value);
+ curPos += 1;
+ }
+ }
+ vector.getOffsetBuffer().setInt((i + 1) *
BaseRepeatedValueVector.OFFSET_WIDTH, curPos);
+ }
+ dataVector.setValueCount(curPos);
+ vector.setLastSet(values.length - 1);
+ vector.setValueCount(values.length);
+ }
+
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE); // deal
with byte buffer allocation
+
+Define data type
+================
+
+Definition of columnar fields for string (name), integer (age) and array
(points):
+
+.. code-block:: java
+ :emphasize-lines: 6,8,12,15
+
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+
+ // create a column data type
Review comment:
Related to cookbook is to show case how java arrow is working. Related
to teach our audience we could define something like this comments on that part
>
All the comments was removed because the title of cookbook also resume very
well the objective of the code
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