Fix "File too large" error for impossible precedence

Author: thomaskrause

graphannis/src/annis/db/aql/operators/precedence.rs

@@ -178,7 +178,8 @@ impl<'a> BinaryOperatorBase for Precedence<'a> {
                 std::ops::Bound::Excluded(max_dist) => max_dist - 1,
             };
             let max_possible_dist = std::cmp::min(max_dist, stats_order.max_depth);
-            let num_of_descendants = max_possible_dist - self.spec.dist.min_dist() + 1;
+            let num_of_descendants =
+                max_possible_dist.saturating_sub(self.spec.dist.min_dist()) + 1;
 
             return Ok(EstimationType::Selectivity(
                 (num_of_descendants as f64) / (stats_order.nodes as f64 / 2.0),

graphannis/tests/searchtest.rs

@@ -364,3 +364,27 @@ fn negative_token_search_applies_leaf_filter() {
         }
     }
 }
+
+#[ignore]
+#[test]
+fn no_error_on_large_token_distance() {
+    let cs = CORPUS_STORAGE.as_ref().unwrap();
+
+    let q = SearchQuery {
+        corpus_names: &["subtok.demo"],
+        query: r#"tok .100 tok"#,
+        query_language: QueryLanguage::AQL,
+        timeout: None,
+    };
+    // There should be an empty result, but no error
+    let result = cs
+        .find(
+            q.clone(),
+            0,
+            Some(1),
+            graphannis::corpusstorage::ResultOrder::Normal,
+        )
+        .unwrap();
+
+    assert_eq!(0, result.len());
+}