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Posted to github@arrow.apache.org by "yahoNanJing (via GitHub)" <gi...@apache.org> on 2023/04/10 11:23:14 UTC
[GitHub] [arrow-datafusion] yahoNanJing opened a new pull request, #5941: Issue 5940
yahoNanJing opened a new pull request, #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941
# Which issue does this PR close?
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Closes #5940.
# Rationale for this change
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After applying patches based on #5866 and #5904, based on the flame graph for q17 generated by
`sudo CARGO_PROFILE_RELEASE_DEBUG=true cargo flamegraph --freq 500 --bin tpch -- benchmark datafusion --path ./data-parquet/ --format parquet --partitions 1 -q 17 --iterations 10`
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# Are there any user-facing changes?
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[GitHub] [arrow-datafusion] yahoNanJing commented on a diff in pull request #5941: Remove unnecessary equality check for JoinHashMap - Issue 5940
Posted by "yahoNanJing (via GitHub)" <gi...@apache.org>.
yahoNanJing commented on code in PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#discussion_r1162238740
##########
datafusion/core/src/physical_plan/joins/hash_join.rs:
##########
@@ -594,16 +593,17 @@ pub fn update_hash(
let hash_values = create_hashes(&keys_values, random_state, hashes_buffer)?;
// insert hashes to key of the hashmap
- for (row, hash_value) in hash_values.iter().enumerate() {
- let item = hash_map
- .0
- .get_mut(*hash_value, |(hash, _)| *hash_value == *hash);
+ let row_start = offset;
+ let row_end = offset + hash_values.len();
+ for (row, hash_value) in (row_start..row_end).zip(hash_values.iter()) {
+ // the hash value is the key, always true
+ let item = hash_map.0.get_mut(*hash_value, |_| true);
Review Comment:
Thanks @Dandandan for pointing it out. You are right. It's my bad. The RawTable utilizes the open addressing policy for looking for matched entries. I'll revert this commit.
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[GitHub] [arrow-datafusion] Dandandan commented on pull request #5941: Remove unnecessary equality check for JoinHashMap - Issue 5940
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#issuecomment-1502178618
It would be nice to show whether we are not getting regressions for other queries.
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Re: [PR] Change back SmallVec to Vec for JoinHashMap - Issue 5940 [arrow-datafusion]
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan closed pull request #5941: Change back SmallVec to Vec for JoinHashMap - Issue 5940
URL: https://github.com/apache/arrow-datafusion/pull/5941
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[GitHub] [arrow-datafusion] alamb commented on pull request #5941: Remove unnecessary equality check for JoinHashMap - Issue 5940
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#issuecomment-1502057461
There is a CI check https://github.com/apache/arrow-datafusion/actions/runs/4657156069/jobs/8241558786?pr=5941 appears to be failing
Given that we have a benchmark that improves (q17) I think we should merge this PR, assuming we can resolve the CI failure satisfactorily.
Thank you for this @yahoNanJing
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Re: [PR] Change back SmallVec to Vec for JoinHashMap - Issue 5940 [arrow-datafusion]
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#issuecomment-1900409350
We have improved the datastructure of join in other ways already, so closing the PR in order to clean it up
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[GitHub] [arrow-datafusion] yahoNanJing commented on pull request #5941: Change back SmallVec to Vec for JoinHashMap - Issue 5940
Posted by "yahoNanJing (via GitHub)" <gi...@apache.org>.
yahoNanJing commented on PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#issuecomment-1502741913
Thanks @Dandandan and @alamb. I tested this PR with other sqls from TPCH. It seems it's not always true of bringing performance benefits. I think we can hold on this PR.
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[GitHub] [arrow-datafusion] yahoNanJing commented on pull request #5941: Issue 5940
Posted by "yahoNanJing (via GitHub)" <gi...@apache.org>.
yahoNanJing commented on PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#issuecomment-1501717963
Hi @Dandandan and @alamb, could you help review this PR?
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[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #5941: Issue 5940
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on code in PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#discussion_r1161804695
##########
datafusion/core/src/physical_plan/joins/hash_join.rs:
##########
@@ -543,7 +542,7 @@ async fn collect_left_input(
)
})? / 7)
.next_power_of_two();
- // 32 bytes per `(u64, SmallVec<[u64; 1]>)`
+ // 32 bytes per `(u64, Vec<[u64; 1]>)`
Review Comment:
This probably is a trade-off, joins with unique keys will probably get slower.
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[GitHub] [arrow-datafusion] alamb commented on pull request #5941: Change back SmallVec to Vec for JoinHashMap - Issue 5940
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#issuecomment-1503092951
Marking to draft so we don't accidentally merge it
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[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #5941: Remove unnecessary equality check for JoinHashMap - Issue 5940
Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on code in PR #5941:
URL: https://github.com/apache/arrow-datafusion/pull/5941#discussion_r1161987716
##########
datafusion/core/src/physical_plan/joins/hash_join.rs:
##########
@@ -594,16 +593,17 @@ pub fn update_hash(
let hash_values = create_hashes(&keys_values, random_state, hashes_buffer)?;
// insert hashes to key of the hashmap
- for (row, hash_value) in hash_values.iter().enumerate() {
- let item = hash_map
- .0
- .get_mut(*hash_value, |(hash, _)| *hash_value == *hash);
+ let row_start = offset;
+ let row_end = offset + hash_values.len();
+ for (row, hash_value) in (row_start..row_end).zip(hash_values.iter()) {
+ // the hash value is the key, always true
+ let item = hash_map.0.get_mut(*hash_value, |_| true);
Review Comment:
The equality check might still be necessary.
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