[SPARK-52232][SQL] Fix non-deterministic queries to produce different results at every step #50957
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… results at every step
cloud-fan
reviewed
May 22, 2025
| val recursionReseeded = if (recursion.deterministic) { | ||
| recursion | ||
| } else { | ||
| recursion.transformExpressionsDown { |
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I think we should use transformAllExpressionsWithSubqueries
cloud-fan
reviewed
May 22, 2025
| } else { | ||
| recursion.transformExpressionsDown { | ||
| case e: ExpressionWithRandomSeed => | ||
| e.withShiftedSeed(currentLevel) |
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does the currentLevel start with 0?
cloud-fan
reviewed
May 22, 2025
| @@ -1267,6 +1267,9 @@ case class Shuffle(child: Expression, randomSeed: Option[Long] = None) extends U | |||
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| override def withNewSeed(seed: Long): Shuffle = copy(randomSeed = Some(seed)) | |||
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| override def withShiftedSeed(shift: Long): Shuffle = | |||
| copy(randomSeed = Some(randomSeed.get + shift)) | |||
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this may cause errors, we should do randomSeed.map(_ + shift)
cloud-fan
reviewed
May 22, 2025
| @@ -260,6 +260,8 @@ case class Uuid(randomSeed: Option[Long] = None) extends LeafExpression with Non | |||
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| override def withNewSeed(seed: Long): Uuid = Uuid(Some(seed)) | |||
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| override def withShiftedSeed(shift: Long): Uuid = Uuid(Some(randomSeed.get + shift)) | |||
cloud-fan
reviewed
May 22, 2025
| @@ -114,6 +115,8 @@ case class Rand(child: Expression, hideSeed: Boolean = false) extends Nondetermi | |||
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| override def withNewSeed(seed: Long): Rand = Rand(Literal(seed, LongType), hideSeed) | |||
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| override def withShiftedSeed(shift: Long): Rand = Rand(Add(child, Literal(shift)), hideSeed) | |||
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Suggested change
| override def withShiftedSeed(shift: Long): Rand = Rand(Add(child, Literal(shift)), hideSeed) | |
| override def withShiftedSeed(shift: Long): Rand = Rand(Add(child, Literal(shift), evalMode = EvalMode.LEGACY), hideSeed) |
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to make sure it won't cause overflow error
cloud-fan
reviewed
May 22, 2025
| @@ -165,6 +168,8 @@ case class Randn(child: Expression, hideSeed: Boolean = false) extends Nondeterm | |||
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| override def withNewSeed(seed: Long): Randn = Randn(Literal(seed, LongType), hideSeed) | |||
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| override def withShiftedSeed(shift: Long): Randn = Randn(Add(child, Literal(shift)), hideSeed) | |||
cloud-fan
reviewed
May 22, 2025
| -- !query output | ||
| org.apache.spark.sql.AnalysisException | ||
| { | ||
| "errorClass" : "ASSIGNMENT_ARITY_MISMATCH", |
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why do we have this error?
cloud-fan
reviewed
May 22, 2025
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| test("Random rCTEs produce different results in different iterations - RAND") { | ||
| val df = sql("""WITH RECURSIVE randoms(val) AS ( | ||
| | SELECT CAST(floor(rand() * 50 + 1) AS INT) |
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shall we specify a seed to make the test result stable?
cloud-fan
reviewed
May 22, 2025
| import org.apache.spark.sql.functions.countDistinct | ||
| import org.apache.spark.sql.test.SharedSparkSession | ||
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| class RecursiveCTESuite extends QueryTest with SharedSparkSession { |
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how does this test suite provide more test coverage in addition to the golden files?
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What changes were proposed in this pull request?
Enable deterministic queries to work with rCTEs. Fix bug where non-deterministic queries produce same result every iteration.
Why are the changes needed?
Currently, recursive CTEs create a new plan for each iteration of the recursion, so the expressions that use randomness "roll-back" to their initial value, causing things like "rand()" to produce the same result every time.
Does this PR introduce any user-facing change?
No.
How was this patch tested?
New tests in golden files.
Was this patch authored or co-authored using generative AI tooling?
No.