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[Parquet] Add BooleanArray based row selection #6624
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The benchmark can take a while to run, here're some of my results visualized by ChatGPT. Note that both x and y axies are in log scale. Selection ratio 1e-5 means 0.0001% of the rows are selected, 0.3 means 30% are selected, and so on. |
Perhaps we could model the number of disjoint selections as opposed to raw selectivity, this more accurately models the sorts of selection one gets from evaluation against the page index (which necessarily has page level granularity) Edit: although the methods benchmarked are those used for late materialization, so perhaps it doesn't matter |
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I've not reviewed in fine detail, but the code looks good to me
I will try and find time to review this today or tomorrow as well -- thank you @XiangpengHao and @tustvold |
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Thanks @XiangpengHao -- I think this is an interesting direction to head (use bitmap for selection). However, I am not sure about this exact implementation)
I left some questions below.
One thing that seems like it might be more useful is to switch RowSelection
into an enum
so we can dynamically switch between the two representations based on what is actually selected
enum RowSelection {
Ranges(Vec<Selection>),
Btitmap(..)
}
I realize one challenge with this is that BooleanArray
is part of arrow and not available in Parquet directly.
/// A selection of rows, similar to [`RowSelection`], but based on a boolean array | ||
#[derive(Debug, Clone, PartialEq, Eq)] | ||
pub struct BooleanRowSelection { | ||
selector: BooleanBuffer, |
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One question I have while reviewing this PR is "why not just use BooleanArray
directly?"
It seems like most of these methods would be generally useful on BooleanArray
(or perhaps as kernels) -- and in fact most of them are already (like union is |
and intersection is &
).
Another thing that might be interesting to do if we really care about performance is to look into implementing in-place updates -- maybe something like https://docs.rs/arrow/latest/arrow/compute/fn.binary_mut.html for BooleanArray)
That should work, my initial thoughts was to only use bitmap-based selectors when evaluating predicates (i.e., when filter pushdown is enabled); and always do range-based selectors otherwise.
I agree that most of the functionality overlaps with |
Marking as draft as I believe we plan additonal work for this PR |
Which issue does this PR close?
Part of #5523
Rationale for this change
Implement the row selection based on BooleanArray.
The implementation only covers the core operations like
union
,intersection
,and_then
, and is already quite large. Once we agree with the generally direction, I'll add remaining implementaions in follow up PRs.What changes are included in this PR?
I added more benchmark to cover different selection ratios, as suggested by @tustvold and @alamb
Are there any user-facing changes?