[score boosting] extract first element of arrays (#6106)

* if a value is an array, extract the first element

* extract variable from geodistance

lib/collection/src/operations/universal_query/formula.rs

@@ -92,6 +92,7 @@ impl ExpressionInternal {
                 by_zero_default,
             ),
             ExpressionInternal::GeoDistance { origin, to } => {
+                payload_vars.insert(to.clone());
                 ParsedExpression::new_geo_distance(origin, to)
             }
             ExpressionInternal::Sqrt(expression_internal) => ParsedExpression::Sqrt(Box::new(

lib/segment/src/index/query_optimization/rescore_formula/value_retriever.rs

@@ -75,6 +75,16 @@ fn payload_variable_retriever(
             |payload| {
                 let values = payload.get_value(&json_path);
                 let value = *values.first()?;
+
+                // not using array wildcard `[]` on a key which has an array value will return the whole
+                // array as one value, let's extract the first element if that is the case.
+                match value {
+                    serde_json::Value::Array(array) if !json_path.has_wildcard_suffix() => {
+                        return array.first().cloned();
+                    }
+                    _ => {}
+                }
+
                 Some(value.clone())
             },
             hw_counter,
@@ -253,12 +263,12 @@ mod tests {
             payload_provider.clone(),
             &hw_counter,
         );
-        for id in 0..2 {
+        for id in 0..=2 {
             let value = retriever(id);
             match id {
                 0 => assert_eq!(value, Some(json!(42))),
                 1 => assert_eq!(value, None),
-                2 => assert_eq!(value, Some(json!(99.0))),
+                2 => assert_eq!(value, Some(json!(99))),
                 _ => unreachable!(),
             }
         }
@@ -270,7 +280,7 @@ mod tests {
             payload_provider.clone(),
             &hw_counter,
         );
-        for id in 0..2 {
+        for id in 0..=2 {
             let value = retriever(id);
             match id {
                 0 => assert_eq!(value, None),
@@ -324,7 +334,7 @@ mod tests {
             payload_provider.clone(),
             &hw_counter,
         );
-        for id in 0..2 {
+        for id in 0..=2 {
             let value = retriever(id);
             match id {
                 0 => assert_eq!(value, Some(json!(42))),
@@ -341,7 +351,7 @@ mod tests {
             payload_provider.clone(),
             &hw_counter,
         );
-        for id in 0..2 {
+        for id in 0..=2 {
             let value = retriever(id);
             match id {
                 0 => assert_eq!(value, None),

lib/segment/src/json_path/mod.rs

@@ -171,6 +171,10 @@ impl JsonPath {
         result
     }
 
+    pub fn has_wildcard_suffix(&self) -> bool {
+        self.rest.last() == Some(&JsonPathItem::WildcardIndex)
+    }
+
     /// Check if a path is included in a list of patterns.
     ///
     /// Basically, it checks if either the pattern or path is a prefix of the other.