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Posted to github@datafusion.apache.org by "korowa (via GitHub)" <gi...@apache.org> on 2024/08/04 18:43:51 UTC
[PR] fix: hash join tests with forced collisions [datafusion]
korowa opened a new pull request, #11806:
URL: https://github.com/apache/datafusion/pull/11806
## Which issue does this PR close?
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Closes #11658.
## Rationale for this change
<!--
Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed.
Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes.
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Some tests in `hash_join.rs` check the number of output batches, and since output batch for `HashJoinExec` is created while matching join keys against hash table built on build-side data (which includes only matching by hashes, comparing actual values is a next step in join execution), these tests are failing with forced collisions (due to equal hashes, all records are considered as matching).
This PR recovers hash join tests by adjusting the numbers of expected batches in case test is running with `force_hash_collisions` feature.
## What changes are included in this PR?
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There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR.
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Different numbers of expected output batches for `force_hash_collisions` feature in hash join tests.
## Are these changes tested?
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2. Serve as another way to document the expected behavior of the code
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Yes
## Are there any user-facing changes?
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No
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Re: [PR] fix: hash join tests with forced collisions [datafusion]
Posted by "comphead (via GitHub)" <gi...@apache.org>.
comphead commented on code in PR #11806:
URL: https://github.com/apache/datafusion/pull/11806#discussion_r1703545148
##########
datafusion/physical-plan/src/joins/hash_join.rs:
##########
@@ -1964,12 +1960,21 @@ mod tests {
assert_eq!(columns, vec!["a1", "b2", "c1", "a1", "b2", "c2"]);
- // expected joined records = 3
- // in case batch_size is 1 - additional empty batch for remaining 3-2 row
- let mut expected_batch_count = div_ceil(3, batch_size);
- if batch_size == 1 {
- expected_batch_count += 1;
- }
+ let expected_batch_count = if cfg!(not(feature = "force_hash_collisions")) {
+ // Expected number of hash table matches = 3
+ // in case batch_size is 1 - additional empty batch for remaining 3-2 row
+ let mut expected_batch_count = div_ceil(3, batch_size);
+ if batch_size == 1 {
+ expected_batch_count += 1;
+ }
+ expected_batch_count
+ } else {
+ // With hash collisions enabled, all records will match each other
+ // and filtered later.
+ // Expected number of matches = 9
+ div_ceil(9, batch_size)
Review Comment:
just wondering will it be 9 for all batch sizes?
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Re: [PR] fix: hash join tests with forced collisions [datafusion]
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb merged PR #11806:
URL: https://github.com/apache/datafusion/pull/11806
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Re: [PR] fix: hash join tests with forced collisions [datafusion]
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on code in PR #11806:
URL: https://github.com/apache/datafusion/pull/11806#discussion_r1704502590
##########
datafusion/physical-plan/src/joins/hash_join.rs:
##########
@@ -2029,12 +2031,21 @@ mod tests {
assert_eq!(columns, vec!["a1", "b2", "c1", "a1", "b2", "c2"]);
- // expected joined records = 3
- // in case batch_size is 1 - additional empty batch for remaining 3-2 row
- let mut expected_batch_count = div_ceil(3, batch_size);
- if batch_size == 1 {
- expected_batch_count += 1;
- }
+ let expected_batch_count = if cfg!(not(feature = "force_hash_collisions")) {
+ // Expected number of hash table matches = 3
+ // in case batch_size is 1 - additional empty batch for remaining 3-2 row
+ let mut expected_batch_count = div_ceil(3, batch_size);
+ if batch_size == 1 {
+ expected_batch_count += 1;
+ }
+ expected_batch_count
+ } else {
+ // With hash collisions enabled, all records will match each other
+ // and filtered later.
+ // Expected number of matches = 9
Review Comment:
Likewise this seems somewhat redundant (and same below)
```suggestion
```
##########
datafusion/physical-plan/src/joins/hash_join.rs:
##########
@@ -1964,12 +1960,21 @@ mod tests {
assert_eq!(columns, vec!["a1", "b2", "c1", "a1", "b2", "c2"]);
- // expected joined records = 3
- // in case batch_size is 1 - additional empty batch for remaining 3-2 row
- let mut expected_batch_count = div_ceil(3, batch_size);
- if batch_size == 1 {
- expected_batch_count += 1;
- }
+ let expected_batch_count = if cfg!(not(feature = "force_hash_collisions")) {
+ // Expected number of hash table matches = 3
+ // in case batch_size is 1 - additional empty batch for remaining 3-2 row
+ let mut expected_batch_count = div_ceil(3, batch_size);
+ if batch_size == 1 {
+ expected_batch_count += 1;
+ }
+ expected_batch_count
+ } else {
+ // With hash collisions enabled, all records will match each other
+ // and filtered later.
+ // Expected number of matches = 9
Review Comment:
nit I think the comment is redundant with the assert right below it
```suggestion
```
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Re: [PR] fix: hash join tests with forced collisions [datafusion]
Posted by "korowa (via GitHub)" <gi...@apache.org>.
korowa commented on code in PR #11806:
URL: https://github.com/apache/datafusion/pull/11806#discussion_r1703600132
##########
datafusion/physical-plan/src/joins/hash_join.rs:
##########
@@ -1964,12 +1960,21 @@ mod tests {
assert_eq!(columns, vec!["a1", "b2", "c1", "a1", "b2", "c2"]);
- // expected joined records = 3
- // in case batch_size is 1 - additional empty batch for remaining 3-2 row
- let mut expected_batch_count = div_ceil(3, batch_size);
- if batch_size == 1 {
- expected_batch_count += 1;
- }
+ let expected_batch_count = if cfg!(not(feature = "force_hash_collisions")) {
+ // Expected number of hash table matches = 3
+ // in case batch_size is 1 - additional empty batch for remaining 3-2 row
+ let mut expected_batch_count = div_ceil(3, batch_size);
+ if batch_size == 1 {
+ expected_batch_count += 1;
+ }
+ expected_batch_count
+ } else {
+ // With hash collisions enabled, all records will match each other
+ // and filtered later.
+ // Expected number of matches = 9
+ div_ceil(9, batch_size)
Review Comment:
Yes, since [create_hashes](https://github.com/apache/datafusion/blob/1d3bdbe14fd01bbd03abeb57d3ec9bc155a36d71/datafusion/common/src/hash_utils.rs#L355) always sets 0 as hash values, with force-collisions feature enabled, the total number of hash table matches will be equal to `left.row_count() * right.row_count()` for each batch size. The result of the output batch count calculation depends on the batch size though, and it's based on the number of matches.
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Re: [PR] fix: hash join tests with forced collisions [datafusion]
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on PR #11806:
URL: https://github.com/apache/datafusion/pull/11806#issuecomment-2271001780
Thanks again @korowa and @comphead
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