[SPARK-20253][SQL] Remove unnecessary nullchecks of a return value from Spark runtime routines in generated Java code

## What changes were proposed in this pull request?

This PR elminates unnecessary nullchecks of a return value from known Spark runtime routines. We know whether a given Spark runtime routine returns ``null`` or not (e.g. ``ArrayData.toDoubleArray()`` never returns ``null``). Thus, we can eliminate a null check for the return value from the Spark runtime routine.

When we run the following example program, now we get the Java code "Without this PR". In this code, since we know ``ArrayData.toDoubleArray()`` never returns ``null```, we can eliminate null checks at lines 90-92, and 97.

```java
val ds = sparkContext.parallelize(Seq(Array(1.1, 2.2)), 1).toDS.cache
ds.count
ds.map(e => e).show
```

Without this PR
```java
/* 050 */   protected void processNext() throws java.io.IOException {
/* 051 */     while (inputadapter_input.hasNext() && !stopEarly()) {
/* 052 */       InternalRow inputadapter_row = (InternalRow) inputadapter_input.next();
/* 053 */       boolean inputadapter_isNull = inputadapter_row.isNullAt(0);
/* 054 */       ArrayData inputadapter_value = inputadapter_isNull ? null : (inputadapter_row.getArray(0));
/* 055 */
/* 056 */       ArrayData deserializetoobject_value1 = null;
/* 057 */
/* 058 */       if (!inputadapter_isNull) {
/* 059 */         int deserializetoobject_dataLength = inputadapter_value.numElements();
/* 060 */
/* 061 */         Double[] deserializetoobject_convertedArray = null;
/* 062 */         deserializetoobject_convertedArray = new Double[deserializetoobject_dataLength];
/* 063 */
/* 064 */         int deserializetoobject_loopIndex = 0;
/* 065 */         while (deserializetoobject_loopIndex < deserializetoobject_dataLength) {
/* 066 */           MapObjects_loopValue2 = (double) (inputadapter_value.getDouble(deserializetoobject_loopIndex));
/* 067 */           MapObjects_loopIsNull2 = inputadapter_value.isNullAt(deserializetoobject_loopIndex);
/* 068 */
/* 069 */           if (MapObjects_loopIsNull2) {
/* 070 */             throw new RuntimeException(((java.lang.String) references[0]));
/* 071 */           }
/* 072 */           if (false) {
/* 073 */             deserializetoobject_convertedArray[deserializetoobject_loopIndex] = null;
/* 074 */           } else {
/* 075 */             deserializetoobject_convertedArray[deserializetoobject_loopIndex] = MapObjects_loopValue2;
/* 076 */           }
/* 077 */
/* 078 */           deserializetoobject_loopIndex += 1;
/* 079 */         }
/* 080 */
/* 081 */         deserializetoobject_value1 = new org.apache.spark.sql.catalyst.util.GenericArrayData(deserializetoobject_convertedArray); /*###*/
/* 082 */       }
/* 083 */       boolean deserializetoobject_isNull = true;
/* 084 */       double[] deserializetoobject_value = null;
/* 085 */       if (!inputadapter_isNull) {
/* 086 */         deserializetoobject_isNull = false;
/* 087 */         if (!deserializetoobject_isNull) {
/* 088 */           Object deserializetoobject_funcResult = null;
/* 089 */           deserializetoobject_funcResult = deserializetoobject_value1.toDoubleArray();
/* 090 */           if (deserializetoobject_funcResult == null) {
/* 091 */             deserializetoobject_isNull = true;
/* 092 */           } else {
/* 093 */             deserializetoobject_value = (double[]) deserializetoobject_funcResult;
/* 094 */           }
/* 095 */
/* 096 */         }
/* 097 */         deserializetoobject_isNull = deserializetoobject_value == null;
/* 098 */       }
/* 099 */
/* 100 */       boolean mapelements_isNull = true;
/* 101 */       double[] mapelements_value = null;
/* 102 */       if (!false) {
/* 103 */         mapelements_resultIsNull = false;
/* 104 */
/* 105 */         if (!mapelements_resultIsNull) {
/* 106 */           mapelements_resultIsNull = deserializetoobject_isNull;
/* 107 */           mapelements_argValue = deserializetoobject_value;
/* 108 */         }
/* 109 */
/* 110 */         mapelements_isNull = mapelements_resultIsNull;
/* 111 */         if (!mapelements_isNull) {
/* 112 */           Object mapelements_funcResult = null;
/* 113 */           mapelements_funcResult = ((scala.Function1) references[1]).apply(mapelements_argValue);
/* 114 */           if (mapelements_funcResult == null) {
/* 115 */             mapelements_isNull = true;
/* 116 */           } else {
/* 117 */             mapelements_value = (double[]) mapelements_funcResult;
/* 118 */           }
/* 119 */
/* 120 */         }
/* 121 */         mapelements_isNull = mapelements_value == null;
/* 122 */       }
/* 123 */
/* 124 */       serializefromobject_resultIsNull = false;
/* 125 */
/* 126 */       if (!serializefromobject_resultIsNull) {
/* 127 */         serializefromobject_resultIsNull = mapelements_isNull;
/* 128 */         serializefromobject_argValue = mapelements_value;
/* 129 */       }
/* 130 */
/* 131 */       boolean serializefromobject_isNull = serializefromobject_resultIsNull;
/* 132 */       final ArrayData serializefromobject_value = serializefromobject_resultIsNull ? null : org.apache.spark.sql.catalyst.expressions.UnsafeArrayData.fromPrimitiveArray(serializefromobject_argValue);
/* 133 */       serializefromobject_isNull = serializefromobject_value == null;
/* 134 */       serializefromobject_holder.reset();
/* 135 */
/* 136 */       serializefromobject_rowWriter.zeroOutNullBytes();
/* 137 */
/* 138 */       if (serializefromobject_isNull) {
/* 139 */         serializefromobject_rowWriter.setNullAt(0);
/* 140 */       } else {
/* 141 */         // Remember the current cursor so that we can calculate how many bytes are
/* 142 */         // written later.
/* 143 */         final int serializefromobject_tmpCursor = serializefromobject_holder.cursor;
/* 144 */
/* 145 */         if (serializefromobject_value instanceof UnsafeArrayData) {
/* 146 */           final int serializefromobject_sizeInBytes = ((UnsafeArrayData) serializefromobject_value).getSizeInBytes();
/* 147 */           // grow the global buffer before writing data.
/* 148 */           serializefromobject_holder.grow(serializefromobject_sizeInBytes);
/* 149 */           ((UnsafeArrayData) serializefromobject_value).writeToMemory(serializefromobject_holder.buffer, serializefromobject_holder.cursor);
/* 150 */           serializefromobject_holder.cursor += serializefromobject_sizeInBytes;
/* 151 */
/* 152 */         } else {
/* 153 */           final int serializefromobject_numElements = serializefromobject_value.numElements();
/* 154 */           serializefromobject_arrayWriter.initialize(serializefromobject_holder, serializefromobject_numElements, 8);
/* 155 */
/* 156 */           for (int serializefromobject_index = 0; serializefromobject_index < serializefromobject_numElements; serializefromobject_index++) {
/* 157 */             if (serializefromobject_value.isNullAt(serializefromobject_index)) {
/* 158 */               serializefromobject_arrayWriter.setNullDouble(serializefromobject_index);
/* 159 */             } else {
/* 160 */               final double serializefromobject_element = serializefromobject_value.getDouble(serializefromobject_index);
/* 161 */               serializefromobject_arrayWriter.write(serializefromobject_index, serializefromobject_element);
/* 162 */             }
/* 163 */           }
/* 164 */         }
/* 165 */
/* 166 */         serializefromobject_rowWriter.setOffsetAndSize(0, serializefromobject_tmpCursor, serializefromobject_holder.cursor - serializefromobject_tmpCursor);
/* 167 */       }
/* 168 */       serializefromobject_result.setTotalSize(serializefromobject_holder.totalSize());
/* 169 */       append(serializefromobject_result);
/* 170 */       if (shouldStop()) return;
/* 171 */     }
/* 172 */   }
```

With this PR (removed most of lines 90-97 in the above code)
```java
/* 050 */   protected void processNext() throws java.io.IOException {
/* 051 */     while (inputadapter_input.hasNext() && !stopEarly()) {
/* 052 */       InternalRow inputadapter_row = (InternalRow) inputadapter_input.next();
/* 053 */       boolean inputadapter_isNull = inputadapter_row.isNullAt(0);
/* 054 */       ArrayData inputadapter_value = inputadapter_isNull ? null : (inputadapter_row.getArray(0));
/* 055 */
/* 056 */       ArrayData deserializetoobject_value1 = null;
/* 057 */
/* 058 */       if (!inputadapter_isNull) {
/* 059 */         int deserializetoobject_dataLength = inputadapter_value.numElements();
/* 060 */
/* 061 */         Double[] deserializetoobject_convertedArray = null;
/* 062 */         deserializetoobject_convertedArray = new Double[deserializetoobject_dataLength];
/* 063 */
/* 064 */         int deserializetoobject_loopIndex = 0;
/* 065 */         while (deserializetoobject_loopIndex < deserializetoobject_dataLength) {
/* 066 */           MapObjects_loopValue2 = (double) (inputadapter_value.getDouble(deserializetoobject_loopIndex));
/* 067 */           MapObjects_loopIsNull2 = inputadapter_value.isNullAt(deserializetoobject_loopIndex);
/* 068 */
/* 069 */           if (MapObjects_loopIsNull2) {
/* 070 */             throw new RuntimeException(((java.lang.String) references[0]));
/* 071 */           }
/* 072 */           if (false) {
/* 073 */             deserializetoobject_convertedArray[deserializetoobject_loopIndex] = null;
/* 074 */           } else {
/* 075 */             deserializetoobject_convertedArray[deserializetoobject_loopIndex] = MapObjects_loopValue2;
/* 076 */           }
/* 077 */
/* 078 */           deserializetoobject_loopIndex += 1;
/* 079 */         }
/* 080 */
/* 081 */         deserializetoobject_value1 = new org.apache.spark.sql.catalyst.util.GenericArrayData(deserializetoobject_convertedArray); /*###*/
/* 082 */       }
/* 083 */       boolean deserializetoobject_isNull = true;
/* 084 */       double[] deserializetoobject_value = null;
/* 085 */       if (!inputadapter_isNull) {
/* 086 */         deserializetoobject_isNull = false;
/* 087 */         if (!deserializetoobject_isNull) {
/* 088 */           Object deserializetoobject_funcResult = null;
/* 089 */           deserializetoobject_funcResult = deserializetoobject_value1.toDoubleArray();
/* 090 */           deserializetoobject_value = (double[]) deserializetoobject_funcResult;
/* 091 */
/* 092 */         }
/* 093 */
/* 094 */       }
/* 095 */
/* 096 */       boolean mapelements_isNull = true;
/* 097 */       double[] mapelements_value = null;
/* 098 */       if (!false) {
/* 099 */         mapelements_resultIsNull = false;
/* 100 */
/* 101 */         if (!mapelements_resultIsNull) {
/* 102 */           mapelements_resultIsNull = deserializetoobject_isNull;
/* 103 */           mapelements_argValue = deserializetoobject_value;
/* 104 */         }
/* 105 */
/* 106 */         mapelements_isNull = mapelements_resultIsNull;
/* 107 */         if (!mapelements_isNull) {
/* 108 */           Object mapelements_funcResult = null;
/* 109 */           mapelements_funcResult = ((scala.Function1) references[1]).apply(mapelements_argValue);
/* 110 */           if (mapelements_funcResult == null) {
/* 111 */             mapelements_isNull = true;
/* 112 */           } else {
/* 113 */             mapelements_value = (double[]) mapelements_funcResult;
/* 114 */           }
/* 115 */
/* 116 */         }
/* 117 */         mapelements_isNull = mapelements_value == null;
/* 118 */       }
/* 119 */
/* 120 */       serializefromobject_resultIsNull = false;
/* 121 */
/* 122 */       if (!serializefromobject_resultIsNull) {
/* 123 */         serializefromobject_resultIsNull = mapelements_isNull;
/* 124 */         serializefromobject_argValue = mapelements_value;
/* 125 */       }
/* 126 */
/* 127 */       boolean serializefromobject_isNull = serializefromobject_resultIsNull;
/* 128 */       final ArrayData serializefromobject_value = serializefromobject_resultIsNull ? null : org.apache.spark.sql.catalyst.expressions.UnsafeArrayData.fromPrimitiveArray(serializefromobject_argValue);
/* 129 */       serializefromobject_isNull = serializefromobject_value == null;
/* 130 */       serializefromobject_holder.reset();
/* 131 */
/* 132 */       serializefromobject_rowWriter.zeroOutNullBytes();
/* 133 */
/* 134 */       if (serializefromobject_isNull) {
/* 135 */         serializefromobject_rowWriter.setNullAt(0);
/* 136 */       } else {
/* 137 */         // Remember the current cursor so that we can calculate how many bytes are
/* 138 */         // written later.
/* 139 */         final int serializefromobject_tmpCursor = serializefromobject_holder.cursor;
/* 140 */
/* 141 */         if (serializefromobject_value instanceof UnsafeArrayData) {
/* 142 */           final int serializefromobject_sizeInBytes = ((UnsafeArrayData) serializefromobject_value).getSizeInBytes();
/* 143 */           // grow the global buffer before writing data.
/* 144 */           serializefromobject_holder.grow(serializefromobject_sizeInBytes);
/* 145 */           ((UnsafeArrayData) serializefromobject_value).writeToMemory(serializefromobject_holder.buffer, serializefromobject_holder.cursor);
/* 146 */           serializefromobject_holder.cursor += serializefromobject_sizeInBytes;
/* 147 */
/* 148 */         } else {
/* 149 */           final int serializefromobject_numElements = serializefromobject_value.numElements();
/* 150 */           serializefromobject_arrayWriter.initialize(serializefromobject_holder, serializefromobject_numElements, 8);
/* 151 */
/* 152 */           for (int serializefromobject_index = 0; serializefromobject_index < serializefromobject_numElements; serializefromobject_index++) {
/* 153 */             if (serializefromobject_value.isNullAt(serializefromobject_index)) {
/* 154 */               serializefromobject_arrayWriter.setNullDouble(serializefromobject_index);
/* 155 */             } else {
/* 156 */               final double serializefromobject_element = serializefromobject_value.getDouble(serializefromobject_index);
/* 157 */               serializefromobject_arrayWriter.write(serializefromobject_index, serializefromobject_element);
/* 158 */             }
/* 159 */           }
/* 160 */         }
/* 161 */
/* 162 */         serializefromobject_rowWriter.setOffsetAndSize(0, serializefromobject_tmpCursor, serializefromobject_holder.cursor - serializefromobject_tmpCursor);
/* 163 */       }
/* 164 */       serializefromobject_result.setTotalSize(serializefromobject_holder.totalSize());
/* 165 */       append(serializefromobject_result);
/* 166 */       if (shouldStop()) return;
/* 167 */     }
/* 168 */   }
```

## How was this patch tested?

Add test suites to ``DatasetPrimitiveSuite``

Author: Kazuaki Ishizaki <ishizaki@jp.ibm.com>

Closes #17569 from kiszk/SPARK-20253.

1 files changed, 10 insertions, 0 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DatasetPrimitiveSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DatasetPrimitiveSuite.scala
index 82b707537e..541565344f 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/DatasetPrimitiveSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/DatasetPrimitiveSuite.scala
@@ -96,6 +96,16 @@ class DatasetPrimitiveSuite extends QueryTest with SharedSQLContext {
     checkDataset(dsBoolean.map(e => !e), false, true)
   }
 
+  test("mapPrimitiveArray") {
+    val dsInt = Seq(Array(1, 2), Array(3, 4)).toDS()
+    checkDataset(dsInt.map(e => e), Array(1, 2), Array(3, 4))
+    checkDataset(dsInt.map(e => null: Array[Int]), null, null)
+
+    val dsDouble = Seq(Array(1D, 2D), Array(3D, 4D)).toDS()
+    checkDataset(dsDouble.map(e => e), Array(1D, 2D), Array(3D, 4D))
+    checkDataset(dsDouble.map(e => null: Array[Double]), null, null)
+  }
+
   test("filter") {
     val ds = Seq(1, 2, 3, 4).toDS()
     checkDataset(