Add protection against test running into an infinite loop (#3186)

Trying to improve the test experience, abort tests in case they are
running into infinite loops when processing continuations.
This assumes that the test data will not produce more than a maximum
number of rows (currently set to 100), and aborts the continuation loop
after that number.
Note that the non-forced-continuation loop does not need that protection
since it will require a "result" line in the yaml to trigger a
continuation , and those are bound by a finite number.

Author: ohadzeliger

yaml-tests/src/main/java/com/apple/foundationdb/relational/yamltests/command/QueryExecutor.java

@@ -51,6 +51,7 @@
 public class QueryExecutor {
     private static final Logger logger = LogManager.getLogger(QueryExecutor.class);
     private static final int FORCED_MAX_ROWS = 1; // The maxRows number to use when we are forcing it on the test
+    private static final int MAX_CONTINUATIONS_ALLOWED = 100;
 
     @Nonnull
     private final String query;
@@ -242,6 +243,7 @@ private Object executeStatementWithForcedContinuations(final @Nonnull Statement
             results.add(resultSet);
             // Have continuations - keep running the query
             Continuation continuation = resultSet.getContinuation();
+            int count = 0;
             while (!continuation.atEnd()) {
                 if (continuation.atBeginning()) {
                     reportTestFailure("Received continuation shouldn't be at beginning");
@@ -257,6 +259,10 @@ private Object executeStatementWithForcedContinuations(final @Nonnull Statement
                         Assertions.assertFalse(hasNext);
                     }
                 }
+                count += 1; // PMD failure for ++
+                if (count > MAX_CONTINUATIONS_ALLOWED) {
+                    reportTestFailure("Too many continuations for query. Test aborted.");
+                }
             }
             // Use first metadata for the aggregated result set as they are all the same
             // Use last continuation