Limit complexity of IntervalQueryBuilderTests#testRandomSource() (#41538)

IntervalsSources can throw IllegalArgumentExceptions if they would produce
too many disjunctions.  To mitigate against this when building random
sources, we limit the depth of the randomly generated source to four
nested sources

Fixes #41402

Author: romseygeek

server/src/test/java/org/elasticsearch/index/query/IntervalQueryBuilderTests.java

@@ -49,26 +49,14 @@ public class IntervalQueryBuilderTests extends AbstractQueryTestCase<IntervalQue
 
     @Override
     protected IntervalQueryBuilder doCreateTestQueryBuilder() {
-        return new IntervalQueryBuilder(STRING_FIELD_NAME, createRandomSource());
-    }
-
-    @Override
-    public void testUnknownField() throws IOException {
-        super.testUnknownField();
+        return new IntervalQueryBuilder(STRING_FIELD_NAME, createRandomSource(0));
     }
 
     private static final String[] filters = new String[]{
         "containing", "contained_by", "not_containing", "not_contained_by",
         "overlapping", "not_overlapping", "before", "after"
     };
 
-    private IntervalsSourceProvider.IntervalFilter createRandomFilter() {
-        if (randomInt(20) > 18) {
-            return new IntervalsSourceProvider.IntervalFilter(createRandomSource(), randomFrom(filters));
-        }
-        return null;
-    }
-
     private static final String MASKED_FIELD = "masked_field";
     private static final String NO_POSITIONS_FIELD = "no_positions_field";
 
@@ -88,42 +76,56 @@ protected void initializeAdditionalMappings(MapperService mapperService) throws
             new CompressedXContent(Strings.toString(mapping)), MapperService.MergeReason.MAPPING_UPDATE);
     }
 
-    private IntervalsSourceProvider createRandomSource() {
-        String useField = rarely() ? MASKED_FIELD : null;
+    private IntervalsSourceProvider createRandomSource(int depth) {
+        if (depth > 3) {
+            return createRandomMatch(depth + 1);
+        }
         switch (randomInt(20)) {
             case 0:
             case 1:
                 int orCount = randomInt(4) + 1;
                 List<IntervalsSourceProvider> orSources = new ArrayList<>();
                 for (int i = 0; i < orCount; i++) {
-                    orSources.add(createRandomSource());
+                    orSources.add(createRandomSource(depth + 1));
                 }
-                return new IntervalsSourceProvider.Disjunction(orSources, createRandomFilter());
+                return new IntervalsSourceProvider.Disjunction(orSources, createRandomFilter(depth + 1));
             case 2:
             case 3:
                 int count = randomInt(5) + 1;
                 List<IntervalsSourceProvider> subSources = new ArrayList<>();
                 for (int i = 0; i < count; i++) {
-                    subSources.add(createRandomSource());
+                    subSources.add(createRandomSource(depth + 1));
                 }
                 boolean ordered = randomBoolean();
                 int maxGaps = randomInt(5) - 1;
-                IntervalsSourceProvider.IntervalFilter filter = createRandomFilter();
+                IntervalsSourceProvider.IntervalFilter filter = createRandomFilter(depth + 1);
                 return new IntervalsSourceProvider.Combine(subSources, ordered, maxGaps, filter);
             default:
-                int wordCount = randomInt(4) + 1;
-                List<String> words = new ArrayList<>();
-                for (int i = 0; i < wordCount; i++) {
-                    words.add(randomRealisticUnicodeOfLengthBetween(4, 20));
-                }
-                String text = String.join(" ", words);
-                boolean mOrdered = randomBoolean();
-                int maxMGaps = randomInt(5) - 1;
-                String analyzer = randomFrom("simple", "keyword", "whitespace");
-                return new IntervalsSourceProvider.Match(text, maxMGaps, mOrdered, analyzer, createRandomFilter(), useField);
+                return createRandomMatch(depth + 1);
         }
     }
 
+    private IntervalsSourceProvider.IntervalFilter createRandomFilter(int depth) {
+        if (depth < 3 && randomInt(20) > 18) {
+            return new IntervalsSourceProvider.IntervalFilter(createRandomSource(depth + 1), randomFrom(filters));
+        }
+        return null;
+    }
+
+    private IntervalsSourceProvider createRandomMatch(int depth) {
+        String useField = rarely() ? MASKED_FIELD : null;
+        int wordCount = randomInt(4) + 1;
+        List<String> words = new ArrayList<>();
+        for (int i = 0; i < wordCount; i++) {
+            words.add(randomRealisticUnicodeOfLengthBetween(4, 20));
+        }
+        String text = String.join(" ", words);
+        boolean mOrdered = randomBoolean();
+        int maxMGaps = randomInt(5) - 1;
+        String analyzer = randomFrom("simple", "keyword", "whitespace");
+        return new IntervalsSourceProvider.Match(text, maxMGaps, mOrdered, analyzer, createRandomFilter(depth + 1), useField);
+    }
+
     @Override
     protected void doAssertLuceneQuery(IntervalQueryBuilder queryBuilder, Query query, SearchContext context) throws IOException {
         assertThat(query, instanceOf(IntervalQuery.class));
@@ -382,6 +384,5 @@ public <FactoryType> FactoryType compile(Script script, ScriptContext<FactoryTyp
         assertEquals(expected, q);
 
     }
-
-
+    
 }