kazuyukitanimura commented on a change in pull request #34611:
URL: https://github.com/apache/spark/pull/34611#discussion_r754843844
##########
File path:
sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedPlainValuesReader.java
##########
@@ -53,19 +53,50 @@ public void skip() {
throw new UnsupportedOperationException();
}
+ private void updateCurrentByte() {
+ try {
+ currentByte = (byte) in.read();
+ } catch (IOException e) {
+ throw new ParquetDecodingException("Failed to read a byte", e);
+ }
+ }
+
@Override
public final void readBooleans(int total, WritableColumnVector c, int rowId)
{
- // TODO: properly vectorize this
- for (int i = 0; i < total; i++) {
- c.putBoolean(rowId + i, readBoolean());
+ int i = 0;
+ if (bitOffset > 0) {
+ i = Math.min(8 - bitOffset, total);
+ c.putBooleans(rowId, i, currentByte, bitOffset);
+ bitOffset = (bitOffset + i) & 7;
+ }
+ for (; i + 7 < total; i += 8) {
+ updateCurrentByte();
+ c.putBooleans(rowId + i, currentByte);
+ }
+ if (i < total) {
+ updateCurrentByte();
+ bitOffset = total - i;
+ c.putBooleans(rowId + i, bitOffset, currentByte, 0);
}
}
@Override
public final void skipBooleans(int total) {
- // TODO: properly vectorize this
- for (int i = 0; i < total; i++) {
- readBoolean();
+ // Using >>3 instead of /8 below. The difference is important when
(total-(8-bitOffset))<0.
+ // E.g. (-1)>>3=(-1) vs. (-1)/8=0. The latter incorrectly enters the
if(numBytesToSkip>=0){.
Review comment:
Let's say `total=8`, `bitOffset=1`, then there are `(8-bitOffset)=7`
bits to skip in the `currentByte`. Now there is still 1 more bit to skip as
`total=8`. So `updateCurrentByte()` needs to be called to update the
`currentByte` and `bitOffset` will be again `1`. In the future, the rest of
the 7bits may be read from the updated `currentByte`. For that reason, we need
to go into the if statement when `numBytesToSkip = (8 - (8 - 1)) >> 3 = 1>>3 =
0`.
The following is a few-lines longer but equivalent condition.
```
if (numBytesToSkip > 0) {
try {
in.skipFully(numBytesToSkip);
} catch (IOException e) {...}
}
if (numBytesToSkip >= 0 && bitOffset > 0) {
updateCurrentByte();
}
```
The scenario is tested at
https://github.com/apache/spark/pull/34611/files#diff-b84cbbb2eadfa9d267b9ab8be2e6be579f28c1813623785c9e667a864f7960e1R194
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