Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/8747#discussion_r41169832
--- Diff:
sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/codegen/UnsafeArrayWriter.java
---
@@ -0,0 +1,179 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalyst.expressions.codegen;
+
+import org.apache.spark.sql.catalyst.expressions.UnsafeArrayData;
+import org.apache.spark.sql.types.Decimal;
+import org.apache.spark.unsafe.Platform;
+import org.apache.spark.unsafe.types.CalendarInterval;
+import org.apache.spark.unsafe.types.UTF8String;
+
+/**
+ * A helper class to write data into global row buffer using
`UnsafeArrayData` format,
+ * used by {@link
org.apache.spark.sql.catalyst.expressions.codegen.GenerateUnsafeProjection}.
+ */
+public class UnsafeArrayWriter {
+
+ private BufferHolder holder;
+ // The offset of the global buffer where we start to write this array.
+ private int startingOffset;
+
+ public void initialize(
+ BufferHolder holder,
+ int numElements,
+ boolean needHeader,
+ int fixedElementSize) {
+
+ // We need 4 bytes each element to store offset.
+ final int fixedSize = 4 * numElements;
+
+ if (needHeader) {
+ // If header is required, we need extra 4 bytes to store the header.
+ holder.grow(fixedSize + 4);
+ // Writes the number of elements into first 4 bytes;
+ Platform.putInt(holder.buffer, holder.cursor, numElements);
+ holder.cursor += 4;
+ } else {
+ holder.grow(fixedSize);
+ }
+
+ this.holder = holder;
+ this.startingOffset = holder.cursor;
+
+ holder.cursor += fixedSize;
+
+ // Grows the global buffer ahead for fixed size data.
+ if (fixedElementSize > 0) {
+ holder.grow(fixedElementSize * numElements);
+ }
+ }
+
+ private long getElementOffset(int ordinal) {
+ return startingOffset + 4 * ordinal;
+ }
+
+ public void setNullAt(int ordinal) {
+ final int relativeOffset = holder.cursor - startingOffset;
+ // Writes negative offset value to represent null element.
+ Platform.putInt(holder.buffer, getElementOffset(ordinal),
-relativeOffset);
+ }
+
+ public void setOffset(int ordinal) {
+ final int relativeOffset = holder.cursor - startingOffset;
+ Platform.putInt(holder.buffer, getElementOffset(ordinal),
relativeOffset);
+ }
+
+
+
+ public void writeCompactDecimal(int ordinal, Decimal input, int
precision, int scale) {
+ // make sure Decimal object has the same scale as DecimalType
+ if (input.changePrecision(precision, scale)) {
+ Platform.putLong(holder.buffer, holder.cursor,
input.toUnscaledLong());
+ setOffset(ordinal);
+ holder.cursor += 8;
+ } else {
+ setNullAt(ordinal);
+ }
+ }
+
+ public void write(int ordinal, Decimal input, int precision, int scale) {
+ // make sure Decimal object has the same scale as DecimalType
+ if (input.changePrecision(precision, scale)) {
+ final byte[] bytes =
input.toJavaBigDecimal().unscaledValue().toByteArray();
+ assert bytes.length <= 16;
+ holder.grow(bytes.length);
+
+ // Write the bytes to the variable length portion.
+ Platform.copyMemory(
+ bytes, Platform.BYTE_ARRAY_OFFSET, holder.buffer, holder.cursor,
bytes.length);
+ setOffset(ordinal);
+ holder.cursor += bytes.length;
+ } else {
+ setNullAt(ordinal);
+ }
+ }
+
+ public void write(int ordinal, UTF8String input) {
+ final int numBytes = input.numBytes();
+
+ // grow the global buffer before writing data.
+ holder.grow(numBytes);
+
+ // Write the bytes to the variable length portion.
+ input.writeToMemory(holder.buffer, holder.cursor);
+
+ setOffset(ordinal);
+
+ // move the cursor forward.
+ holder.cursor += numBytes;
+ }
+
+ public void write(int ordinal, byte[] input) {
+ // grow the global buffer before writing data.
+ holder.grow(input.length);
+
+ // Write the bytes to the variable length portion.
+ Platform.copyMemory(
+ input, Platform.BYTE_ARRAY_OFFSET, holder.buffer, holder.cursor,
input.length);
+
+ setOffset(ordinal);
+
+ // move the cursor forward.
+ holder.cursor += input.length;
+ }
+
+ public void write(int ordinal, CalendarInterval input) {
+ // grow the global buffer before writing data.
+ holder.grow(16);
+
+ // Write the months and microseconds fields of Interval to the
variable length portion.
+ Platform.putLong(holder.buffer, holder.cursor, input.months);
+ Platform.putLong(holder.buffer, holder.cursor + 8, input.microseconds);
+
+ setOffset(ordinal);
+
+ // move the cursor forward.
+ holder.cursor += 16;
+ }
+
+
+
+ // If this array is already an UnsafeArray, we don't need to go through
all elements, we can
+ // directly write it.
+ public static void directWrite(
+ BufferHolder holder,
+ UnsafeArrayData input,
+ boolean needHeader) {
+ final int numBytes = input.getSizeInBytes();
+
+ if (needHeader) {
+ // If header is required, we need extra 4 bytes to store the header.
+ holder.grow(numBytes + 4);
+ // Writes the number of elements into first 4 bytes;
+ Platform.putInt(holder.buffer, holder.cursor, input.numElements());
--- End diff --
Same to here, it's better to move this out of this method.
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