I think we can copy all encoded data into a ByteBuffer once, and unpack
values in the loop
while (valueIndex < this.currentCount) {
// values are bit packed 8 at a time, so reading bitWidth will always
work
this.packer.unpack8Values(buffer, buffer.position() + valueIndex,
this.currentBuffer, valueIndex);
valueIndex += 8;
}
Sean Owen <[email protected]> 于2020年9月14日周一 上午10:40写道：
> It certainly can't be called once - it's reading different data each time.
> There might be a faster way to do it, I don't know. Do you have ideas?
>
> On Sun, Sep 13, 2020 at 9:25 PM Chang Chen <[email protected]> wrote:
> >
> > Hi export
> >
> > it looks like there is a hot spot in
> VectorizedRleValuesReader#readNextGroup()
> >
> > case PACKED:
> > int numGroups = header >>> 1;
> > this.currentCount = numGroups * 8;
> >
> > if (this.currentBuffer.length < this.currentCount) {
> > this.currentBuffer = new int[this.currentCount];
> > }
> > currentBufferIdx = 0;
> > int valueIndex = 0;
> > while (valueIndex < this.currentCount) {
> > // values are bit packed 8 at a time, so reading bitWidth will
> always work
> > ByteBuffer buffer = in.slice(bitWidth);
> > this.packer.unpack8Values(buffer, buffer.position(),
> this.currentBuffer, valueIndex);
> > valueIndex += 8;
> > }
> >
> >
> > Per my profile, the codes will spend 30% time of readNextGrou() on slice
> ， why we can't call slice out of the loop？
>
