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[MINOR]: Add a test case for when target partition is 1, no hash repartition is added to the plan. #8757

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Jan 5, 2024
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[MINOR]: Add a test case for when target partition is 1, no hash repartition is added to the plan. #8757

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3 changes: 1 addition & 2 deletions datafusion/core/src/physical_optimizer/enforce_distribution.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -927,9 +927,8 @@ fn add_hash_on_top(
n_target: usize,
repartition_beneficial_stats: bool,
) -> Result<DistributionContext> {
let partition_count = input.plan.output_partitioning().partition_count();
// Early return if hash repartition is unnecessary
if n_target == partition_count && n_target == 1 {
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I think previous check was wrong, partition count equality doesn't mean their hash requirement is satisfied. However, when target is 1 hash requirement is trivially satisfied

if n_target == 1 {
return Ok(input);
}

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32 changes: 32 additions & 0 deletions datafusion/sqllogictest/test_files/join.slt
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Expand Up @@ -626,6 +626,38 @@ Alice 100 Alice 1
Alice 50 Alice 2
Alice 100 Alice 2

statement ok
set datafusion.execution.target_partitions = 1;

statement ok
set datafusion.optimizer.repartition_joins = true;

# make sure when target partition is 1, hash repartition is not added
# to the final plan.
query TT
EXPLAIN SELECT *
FROM t1,
t1 as t2
WHERE t1.a=t2.a;
----
logical_plan
Inner Join: t1.a = t2.a
--TableScan: t1 projection=[a, b]
--SubqueryAlias: t2
----TableScan: t1 projection=[a, b]
physical_plan
CoalesceBatchesExec: target_batch_size=8192
--HashJoinExec: mode=CollectLeft, join_type=Inner, on=[(a@0, a@0)]
----MemoryExec: partitions=1, partition_sizes=[1]
----MemoryExec: partitions=1, partition_sizes=[1]

# Reset the configs to old values
statement ok
set datafusion.execution.target_partitions = 4;

statement ok
set datafusion.optimizer.repartition_joins = false;

statement ok
DROP TABLE t1;

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