Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/8747#discussion_r40958537
--- Diff:
sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/codegen/UnsafeRowWriter.java
---
@@ -0,0 +1,218 @@
+/*
+ * 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.UnsafeRow;
+import org.apache.spark.sql.types.Decimal;
+import org.apache.spark.unsafe.Platform;
+import org.apache.spark.unsafe.array.ByteArrayMethods;
+import org.apache.spark.unsafe.bitset.BitSetMethods;
+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 `UnsafeRow`
format,
+ * used by {@link
org.apache.spark.sql.catalyst.expressions.codegen.GenerateUnsafeProjection}.
+ */
+public class UnsafeRowWriter {
+
+ private GlobalBufferHolder holder;
+ // The offset of the global buffer where we start to write this row.
+ private int startingOffset;
+ private int nullBitsSize;
+
+ public void initialize(GlobalBufferHolder holder, int numFields) {
+ this.holder = holder;
+ this.startingOffset = holder.cursor;
+ this.nullBitsSize = UnsafeRow.calculateBitSetWidthInBytes(numFields);
+
+ // grow the global buffer to make sure it has enough space to write
fixed-length data.
+ final int fixedSize = nullBitsSize + 8 * numFields;
+ holder.grow(fixedSize);
+ holder.cursor += fixedSize;
+
+ // zero-out the null bits region
+ for (int i = 0; i < nullBitsSize; i += 8) {
+ Platform.putLong(holder.buffer, startingOffset + i, 0L);
+ }
+ }
+
+ private void zeroOutPaddingBytes(int numBytes) {
+ if ((numBytes & 0x07) > 0) {
+ Platform.putLong(holder.buffer, holder.cursor + ((numBytes >> 3) <<
3), 0L);
+ }
+ }
+
+ public void setNullAt(int ordinal) {
+ BitSetMethods.set(holder.buffer, startingOffset, ordinal);
+ Platform.putLong(holder.buffer, getFieldOffset(ordinal), 0L);
+ }
+
+ public long getFieldOffset(int ordinal) {
+ return startingOffset + nullBitsSize + 8 * ordinal;
+ }
+
+ public void setOffsetAndSize(int ordinal, long size) {
+ setOffsetAndSize(ordinal, holder.cursor, size);
+ }
+
+ public void setOffsetAndSize(int ordinal, long currentCursor, long size)
{
+ final long relativeOffset = currentCursor - startingOffset;
+ final long fieldOffset = getFieldOffset(ordinal);
+ final long offsetAndSize = (relativeOffset << 32) | size;
+
+ Platform.putLong(holder.buffer, fieldOffset, offsetAndSize);
+ }
+
+ // Do word alignment for this row and return the number of bytes padded.
+ // todo: remove this after we make unsafe array data word align.
+ public void alignWords(int numBytes) {
+ final int remainder = numBytes & 0x07;
+
+ if (remainder > 0) {
+ final int paddingBytes = 8 - remainder;
+ holder.grow(paddingBytes);
+
+ final byte[] orignalValues = new byte[remainder];
+ Platform.copyMemory(
+ holder.buffer,
+ holder.cursor - remainder,
+ orignalValues,
+ Platform.BYTE_ARRAY_OFFSET,
+ remainder);
+
+ Platform.putLong(holder.buffer, holder.cursor - remainder, 0);
+
+ Platform.copyMemory(
+ orignalValues,
+ Platform.BYTE_ARRAY_OFFSET,
+ holder.buffer,
+ holder.cursor - remainder,
+ remainder);
+
+ holder.cursor += paddingBytes;
+ }
+ }
+
+
+
+ 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, getFieldOffset(ordinal),
input.toUnscaledLong());
+ } else {
+ setNullAt(ordinal);
+ }
+ }
+
+ public void write(int ordinal, Decimal input, int precision, int scale) {
+ // grow the global buffer before writing data.
+ holder.grow(16);
+
+ // zero-out the bytes
+ Platform.putLong(holder.buffer, holder.cursor, 0L);
+ Platform.putLong(holder.buffer, holder.cursor + 8, 0L);
+
+ // Make sure Decimal object has the same scale as DecimalType.
+ // Note that we may pass in null Decimal object to set null for it.
+ if (input == null || !input.changePrecision(precision, scale)) {
+ BitSetMethods.set(holder.buffer, startingOffset, ordinal);
+ // keep the offset for future update
+ final long relativeOffset = holder.cursor - startingOffset;
+ Platform.putLong(holder.buffer, getFieldOffset(ordinal),
relativeOffset << 32);
--- End diff --
setOffsetAndSize(ordinal, 0)
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