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LUCENE-9418: Fix ordered intervals over interleaved terms (#1618)

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Given the input text 'A B A C', an ordered interval 'A B C' will currently return an incorrect
internal [2, 3] in addition to the correct [0, 3] interval. This is due to a bug in the ORDERED
algorithm, where we assume that after the first interval is returned, the sub-intervals are
always in-order. This assumption only holds during minimization, as minimizing an interval
may move the earlier terms beyond the trailing terms.

For example, after the initial [0, 3] interval is found above, the algorithm will attempt to
minimize it by advancing A to [2,2]. Because this is still before C at [3,3], but after B at
[1,1], we then try advancing B, leaving it at [Inf,Inf]. Minimization has failed, so we return
the original interval of [0,3]. However, when we come to retrieve the next interval, our
subintervals look like this: A[2,2], B[Inf,Inf], C[3,3] - the assumption that they are in order
is broken. The algorithm sees that A is before B, assumes that therefore all subsequent
subintervals are in order, and returns the new interval.

This commit fixes things by changing the assumption of ordering to only hold during
minimization. When first finding a candidate interval, the algorithm now checks that
all sub-intervals appear in order.
This commit is contained in:
Alan Woodward 2020-06-30 09:13:55 +01:00 committed by GitHub
parent 0cc45f6cdf
commit 3ff331072a
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 26 additions and 3 deletions
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4
lucene/queries/src/java/org/apache/lucene/queries/intervals/OrderedIntervalsSource.java
View File

@ -133,12 +133,13 @@ class OrderedIntervalsSource extends ConjunctionIntervalsSource {
public int nextInterval() throws IOException {
start = end = slop = IntervalIterator.NO_MORE_INTERVALS;
int lastStart = Integer.MAX_VALUE;
boolean minimizing = false;
i = 1;
while (true) {
while (true) {
if (subIterators.get(i - 1).end() >= lastStart)
return start;
if (i == subIterators.size() || subIterators.get(i).start() > subIterators.get(i - 1).end())
if (i == subIterators.size() || (minimizing && subIterators.get(i).start() > subIterators.get(i - 1).end()))
break;
do {
if (subIterators.get(i).end() >= lastStart || subIterators.get(i).nextInterval() == IntervalIterator.NO_MORE_INTERVALS)
@ -160,6 +161,7 @@ class OrderedIntervalsSource extends ConjunctionIntervalsSource {
i = 1;
if (subIterators.get(0).nextInterval() == IntervalIterator.NO_MORE_INTERVALS)
return start;
minimizing = true;
}
}

10
lucene/queries/src/test/org/apache/lucene/queries/intervals/TestIntervalQuery.java
View File

@ -73,7 +73,8 @@ public class TestIntervalQuery extends LuceneTestCase {
"coordinate genome mapping research",
"coordinate genome research",
"greater new york",
"x x x x x intend x x x message x x x message x x x addressed x x"
"x x x x x intend x x x message x x x message x x x addressed x x",
"issue with intervals queries from search engine. So it's a big issue for us as we need to do ordered searches. Thank you to help us concerning that issue"
};
private void checkHits(Query query, int[] results) throws IOException {
@ -262,6 +263,13 @@ public class TestIntervalQuery extends LuceneTestCase {
checkHits(q, new int[]{ 6, 7 });
}
public void testOrderedWithGaps() throws IOException {
Query q = new IntervalQuery(field, Intervals.maxgaps(1, Intervals.ordered(
Intervals.term("issue"), Intervals.term("search"), Intervals.term("ordered")
)));
checkHits(q, new int[]{});
}
public void testNestedOrInContainedBy() throws IOException {
Query q = new IntervalQuery(field, Intervals.containedBy(
Intervals.term("genome"),

15
lucene/queries/src/test/org/apache/lucene/queries/intervals/TestIntervals.java
View File

@ -73,7 +73,7 @@ public class TestIntervals extends LuceneTestCase {
private static String field2_docs[] = {
"In Xanadu did Kubla Khan a stately pleasure dome decree",
"Where Alph the sacred river ran through caverns measureless to man",
"Down to a sunless sea",
"a b a c b a b c",
"So thrice five miles of fertile ground",
"Pease hot porridge porridge",
"w1 w2 w3 w4 w1 w6 w3 w8 w4 w7 w1 w6"
@ -525,6 +525,14 @@ public class TestIntervals extends LuceneTestCase {
assertEquals(4, source.minExtent());
}
public void testInterleavedOrdered() throws IOException {
IntervalsSource source = Intervals.ordered(Intervals.term("a"), Intervals.term("b"), Intervals.term("c"));
checkIntervals(source, "field2", 1, new int[][]{
{}, {}, { 0, 3, 5, 7 }, {}, {}, {}
});
assertGaps(source, 2, "field2", new int[]{ 1, 0 });
}
public void testUnorderedDistinct() throws IOException {
checkIntervals(Intervals.unorderedNoOverlaps(Intervals.term("pease"), Intervals.term("pease")),
"field1", 3, new int[][]{
@ -670,6 +678,11 @@ public class TestIntervals extends LuceneTestCase {
assertMatch(mi, 0, 3, 0, 11);
assertEquals(3, source.minExtent());
assertEquals(source, source);
assertEquals(source, Intervals.maxgaps(1,
Intervals.unordered(Intervals.term("w1"), Intervals.term("w3"), Intervals.term("w4"))));
assertNotEquals(source, Intervals.maxgaps(2,
Intervals.unordered(Intervals.term("w1"), Intervals.term("w3"), Intervals.term("w4"))));
}