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Posted to github@arrow.apache.org by "Dandandan (via GitHub)" <gi...@apache.org> on 2023/06/30 14:29:56 UTC
[GitHub] [arrow-datafusion] Dandandan opened a new pull request, #6811: Add fetch to sort preserving merge exec
Dandandan opened a new pull request, #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811
# Which issue does this PR close?
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Closes #6000
# Rationale for this change
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[GitHub] [arrow-datafusion] mustafasrepo commented on a diff in pull request #6811: Add fetch to `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "mustafasrepo (via GitHub)" <gi...@apache.org>.
mustafasrepo commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1250382912
##########
datafusion/proto/src/physical_plan/mod.rs:
##########
@@ -692,7 +692,14 @@ impl AsExecutionPlan for PhysicalPlanNode {
}
})
.collect::<Result<Vec<_>, _>>()?;
- Ok(Arc::new(SortPreservingMergeExec::new(exprs, input)))
+ let fetch = if sort.fetch == -1 {
Review Comment:
```suggestion
let fetch = if sort.fetch < 0 {
```
Maybe this version is safer. Also `Sort` uses this paradigm
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[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #6811: Add fetch to sort `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1249555982
##########
datafusion/core/src/physical_plan/sorts/merge.rs:
##########
@@ -227,11 +239,21 @@ impl<C: Cursor> SortPreservingMergeStream<C> {
if self.advance(stream_idx) {
self.loser_tree_adjusted = false;
self.in_progress.push_row(stream_idx);
- if self.in_progress.len() < self.batch_size {
+
Review Comment:
Makes sense, otherwise we could maybe need two separate implementations (with/without fetch)
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[GitHub] [arrow-datafusion] mustafasrepo commented on a diff in pull request #6811: Add fetch to `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "mustafasrepo (via GitHub)" <gi...@apache.org>.
mustafasrepo commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1250361516
##########
datafusion/core/src/physical_plan/sorts/merge.rs:
##########
@@ -140,6 +143,12 @@ struct SortPreservingMergeStream<C> {
/// Vector that holds cursors for each non-exhausted input partition
cursors: Vec<Option<C>>,
+
+ /// Optional number of rows to fetch
+ fetch: Option<usize>,
+
+ /// number of rows produces
Review Comment:
```suggestion
/// number of rows produced
```
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[GitHub] [arrow-datafusion] ozankabak commented on a diff in pull request #6811: Add fetch to sort `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "ozankabak (via GitHub)" <gi...@apache.org>.
ozankabak commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1248924600
##########
datafusion/core/src/physical_optimizer/sort_enforcement.rs:
##########
@@ -801,6 +803,22 @@ fn get_sort_exprs(sort_any: &Arc<dyn ExecutionPlan>) -> Result<&[PhysicalSortExp
}
}
+/// gets
Review Comment:
I think you forgot to complete this comment
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[GitHub] [arrow-datafusion] alamb commented on pull request #6811: Add fetch to `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#issuecomment-1619020334
Thanks everyone -- this looks like it was a great team effort 👍
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[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #6811: Add fetch to sort `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1248935188
##########
datafusion/core/src/physical_plan/sorts/sort.rs:
##########
@@ -285,14 +286,13 @@ impl ExternalSorter {
})
.collect::<Result<_>>()?;
- // TODO: Pushdown fetch to streaming merge (#6000)
-
streaming_merge(
streams,
self.schema.clone(),
&self.expr,
metrics,
self.batch_size,
+ self.fetch,
Review Comment:
This was removed a few months ago to use `streaming_merge` in `SortExec` causing `SortExec` to spill even with a (low) `fetch`.
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[GitHub] [arrow-datafusion] Dandandan merged pull request #6811: Add fetch to `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan merged PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811
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[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #6811: Add fetch to sort `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1249446929
##########
datafusion/core/src/physical_plan/sorts/merge.rs:
##########
@@ -227,11 +239,21 @@ impl<C: Cursor> SortPreservingMergeStream<C> {
if self.advance(stream_idx) {
self.loser_tree_adjusted = false;
self.in_progress.push_row(stream_idx);
- if self.in_progress.len() < self.batch_size {
+
+ // stop sorting if fetch has been reached
+ if self
Review Comment:
Nit: this might be easier to read if you moved the "fetch_reached" into its own function
like
```rust
if self.fetch_reached() {
self.aborted = true;
} else { ..
```
##########
datafusion/core/src/physical_plan/sorts/sort_preserving_merge.rs:
##########
@@ -71,6 +71,8 @@ pub struct SortPreservingMergeExec {
expr: Vec<PhysicalSortExpr>,
/// Execution metrics
metrics: ExecutionPlanMetricsSet,
+ /// Optional number of rows to fetch
Review Comment:
```suggestion
/// Optional number of rows to fetch. Stops producing rows after this fetch
```
##########
datafusion/core/tests/sqllogictests/test_files/tpch/q16.slt.part:
##########
@@ -67,7 +67,7 @@ Limit: skip=0, fetch=10
------------------TableScan: supplier projection=[s_suppkey, s_comment], partial_filters=[supplier.s_comment LIKE Utf8("%Customer%Complaints%")]
physical_plan
GlobalLimitExec: skip=0, fetch=10
---SortPreservingMergeExec: [supplier_cnt@3 DESC,p_brand@0 ASC NULLS LAST,p_type@1 ASC NULLS LAST,p_size@2 ASC NULLS LAST]
+--SortPreservingMergeExec: [supplier_cnt@3 DESC,p_brand@0 ASC NULLS LAST,p_type@1 ASC NULLS LAST,p_size@2 ASC NULLS LAST], fetch=10
Review Comment:
👍
##########
datafusion/core/src/physical_plan/sorts/sort.rs:
##########
@@ -285,14 +286,13 @@ impl ExternalSorter {
})
.collect::<Result<_>>()?;
- // TODO: Pushdown fetch to streaming merge (#6000)
Review Comment:
🎉
##########
datafusion/core/src/physical_plan/sorts/merge.rs:
##########
@@ -227,11 +239,21 @@ impl<C: Cursor> SortPreservingMergeStream<C> {
if self.advance(stream_idx) {
self.loser_tree_adjusted = false;
self.in_progress.push_row(stream_idx);
- if self.in_progress.len() < self.batch_size {
+
Review Comment:
This is the hot path for SortPreservingMerge -- I suspect adding an extra check for fetch won't impact performance in any measurable way, but it might be worth while checking the benchmarks
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[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #6811: Add fetch to `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1251224417
##########
datafusion/core/src/physical_plan/sorts/merge.rs:
##########
@@ -227,11 +239,21 @@ impl<C: Cursor> SortPreservingMergeStream<C> {
if self.advance(stream_idx) {
self.loser_tree_adjusted = false;
self.in_progress.push_row(stream_idx);
- if self.in_progress.len() < self.batch_size {
+
Review Comment:
As benchmarks showed no significant difference, I kept this check in the hot path.
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[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #6811: Add fetch to sort `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1248924899
##########
datafusion/core/src/physical_optimizer/sort_enforcement.rs:
##########
@@ -801,6 +803,22 @@ fn get_sort_exprs(sort_any: &Arc<dyn ExecutionPlan>) -> Result<&[PhysicalSortExp
}
}
+/// gets
Review Comment:
thanks
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[GitHub] [arrow-datafusion] jychen7 commented on a diff in pull request #6811: Add fetch to sort `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "jychen7 (via GitHub)" <gi...@apache.org>.
jychen7 commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1249569218
##########
datafusion/core/src/physical_optimizer/sort_enforcement.rs:
##########
Review Comment:
do we want to pass `sort_exec.fetch()` to the new `SortPreservingMergeExec` as well?
https://github.com/apache/arrow-datafusion/blob/99170b942d91fb419d22faaadd72616bf59a0b87/datafusion/core/src/physical_optimizer/sort_enforcement.rs#L553-L558
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[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #6811: Add fetch to sort `SortPreservingMergeExec` and `SortPreservingMergeStream`
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on code in PR #6811:
URL: https://github.com/apache/arrow-datafusion/pull/6811#discussion_r1248935188
##########
datafusion/core/src/physical_plan/sorts/sort.rs:
##########
@@ -285,14 +286,13 @@ impl ExternalSorter {
})
.collect::<Result<_>>()?;
- // TODO: Pushdown fetch to streaming merge (#6000)
-
streaming_merge(
streams,
self.schema.clone(),
&self.expr,
metrics,
self.batch_size,
+ self.fetch,
Review Comment:
This was moved in a PR to use `streaming_merge` in `SortExec` causing `SortExec` to spill even with a (low) `fetch`.
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