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[SPARK-32115][SQL] Fix SUBSTRING to handle integer overflows #28937

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[SPARK-32115][SQL] Fix SUBSTRING to handle integer overflows #28937

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5f109a8
fix
xuanyuanking Jun 28, 2020
4dcfe81
address comments
xuanyuanking Jun 28, 2020
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11 changes: 10 additions & 1 deletion common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
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Original file line number Diff line number Diff line change
Expand Up @@ -341,8 +341,17 @@ public UTF8String substringSQL(int pos, int length) {
// to the -ith element before the end of the sequence. If a start index i is 0, it
// refers to the first element.
int len = numChars();
// `len + pos` does not overflow as `len >= 0`.
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@kiszk kiszk Jun 28, 2020

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What happens if len = 10 and pos = Integer.MIN_VALUE. I guess that start would have an incorrect value.

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@xuanyuanking xuanyuanking Jun 28, 2020

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The negative pos here refers to the -ith element before the end of the sequence, so if pos = Integer.MIN_VALUE, then the start should be pos + len. The final result of EMPTY_UTF8 will be returned by substring when its param start and until are both negative. I also added a UT in 4dcfe81.

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@kiszk kiszk Jun 28, 2020

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I made misunderstaning. Thank you for clarification and adding a test.

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@xuanyuanking xuanyuanking Jun 30, 2020

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Thanks for reviewing!

int start = (pos > 0) ? pos -1 : ((pos < 0) ? len + pos : 0);
int end = (length == Integer.MAX_VALUE) ? len : start + length;

int end;
if ((long) start + length > Integer.MAX_VALUE) {
end = Integer.MAX_VALUE;
} else if ((long) start + length < Integer.MIN_VALUE) {
end = Integer.MIN_VALUE;
} else {
end = start + length;
}
return substring(start, end);
}

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4 changes: 4 additions & 0 deletions common/unsafe/src/test/java/org/apache/spark/unsafe/types/UTF8StringSuite.java
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Expand Up @@ -390,6 +390,10 @@ public void substringSQL() {
assertEquals(fromString("example"), e.substringSQL(0, Integer.MAX_VALUE));
assertEquals(fromString("example"), e.substringSQL(1, Integer.MAX_VALUE));
assertEquals(fromString("xample"), e.substringSQL(2, Integer.MAX_VALUE));
assertEquals(EMPTY_UTF8, e.substringSQL(-100, -100));
assertEquals(EMPTY_UTF8, e.substringSQL(-1207959552, -1207959552));
assertEquals(fromString("pl"), e.substringSQL(-3, 2));
assertEquals(EMPTY_UTF8, e.substringSQL(Integer.MIN_VALUE, 6));
}

@Test
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4 changes: 4 additions & 0 deletions ...yst/src/test/scala/org/apache/spark/sql/catalyst/expressions/StringExpressionsSuite.scala
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Expand Up @@ -236,6 +236,10 @@ class StringExpressionsSuite extends SparkFunSuite with ExpressionEvalHelper {
"xample",
row)

// Substring with from negative position with negative length
checkEvaluation(Substring(s, Literal.create(-1207959552, IntegerType),
Literal.create(-1207959552, IntegerType)), "", row)

val s_notNull = 'a.string.notNull.at(0)

assert(Substring(s, Literal.create(0, IntegerType), Literal.create(2, IntegerType)).nullable)
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