Stelyus opened a new pull request #35231:
URL: https://github.com/apache/spark/pull/35231
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### What changes were proposed in this pull request?
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When using non-deterministic function, the method getAllValidConstraints can
throw an OOM
```
protected def getAllValidConstraints(projectList: Seq[NamedExpression]):
ExpressionSet = {
var allConstraints = child.constraints
projectList.foreach {
case a @ Alias(l: Literal, _) =>
allConstraints += EqualNullSafe(a.toAttribute, l)
case a @ Alias(e, _) =>
// For every alias in `projectList`, replace the reference in
constraints by its attribute.
allConstraints ++= allConstraints.map(_ transform {
case expr: Expression if expr.semanticEquals(e) =>
a.toAttribute
})
allConstraints += EqualNullSafe(e, a.toAttribute)
case _ => // Don't change.
}
allConstraints
}
```
In particular, this line `allConstraints ++= allConstraints.map(...)` can
generate an exponential number of expressions
This is because non deterministic functions are considered unique in a
ExpressionSet
Therefore, the number of non-deterministic expressions double every time we
go through this line
We can filter and keep only deterministic expression because
1 - the `semanticEquals` automatically discard non deterministic expressions
2 - this method is only used in one code path, and we keep only determinic
expressions
```
lazy val constraints: ExpressionSet = {
if (conf.constraintPropagationEnabled) {
validConstraints
.union(inferAdditionalConstraints(validConstraints))
.union(constructIsNotNullConstraints(validConstraints, output))
.filter { c =>
c.references.nonEmpty && c.references.subsetOf(outputSet) &&
c.deterministic
}
} else {
ExpressionSet()
}
}
```
### Why are the changes needed?
It can lead to an exponential number of expressions and / or OOM
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
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Local test
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