Handle QueryString function

Author: julian-elastic

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/fulltext/QueryString.java

@@ -60,13 +60,14 @@
 import static org.elasticsearch.index.query.QueryStringQueryBuilder.TIME_ZONE_FIELD;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.FIRST;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.SECOND;
-import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isNotNullAndFoldable;
+import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isNotNull;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isType;
 import static org.elasticsearch.xpack.esql.core.type.DataType.BOOLEAN;
 import static org.elasticsearch.xpack.esql.core.type.DataType.FLOAT;
 import static org.elasticsearch.xpack.esql.core.type.DataType.INTEGER;
 import static org.elasticsearch.xpack.esql.core.type.DataType.KEYWORD;
 import static org.elasticsearch.xpack.esql.core.type.DataType.TEXT;
+import static org.elasticsearch.xpack.esql.expression.function.FunctionUtils.resolveTypeQuery;
 
 /**
  * Full text function that performs a {@link QueryStringQuery} .
@@ -309,9 +310,17 @@ public Expression options() {
     public static final Set<DataType> QUERY_DATA_TYPES = Set.of(KEYWORD, TEXT);
 
     private TypeResolution resolveQuery() {
-        return isType(query(), QUERY_DATA_TYPES::contains, sourceText(), FIRST, "keyword, text").and(
-            isNotNullAndFoldable(query(), sourceText(), FIRST)
+        TypeResolution result = isType(query(), QUERY_DATA_TYPES::contains, sourceText(), FIRST, "keyword, text").and(
+            isNotNull(query(), sourceText(), FIRST)
         );
+        if (result.unresolved()) {
+            return result;
+        }
+        result = resolveTypeQuery(query(), sourceText());
+        if (result.equals(TypeResolution.TYPE_RESOLVED) == false) {
+            return result;
+        }
+        return TypeResolution.TYPE_RESOLVED;
     }
 
     private Map<String, Object> queryStringOptions() throws InvalidArgumentException {

x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/esql/230_folding.yml

@@ -241,3 +241,41 @@ Foldable query using MULTI_MATCH on name but with non-foldable expression:
   - match: { error.type: "verification_exception" }
   - contains: { error.reason: "Query must be a valid string in [MULTI_MATCH(CONCAT(\"Bob \", name), name)], found [CONCAT(\"Bob \", name)]" }
 
+---
+
+Foldable query using QSTR on name:
+  - do:
+      esql.query:
+        body:
+          query: |
+            FROM employees
+            | WHERE QSTR(CONCAT("name:", "Bob*"))
+            | KEEP hire_date, salary, salary_change, salary_change_long, name
+            | LIMIT 5
+  - match: { columns.0.name: "hire_date" }
+  - match: { columns.1.name: "salary" }
+  - match: { columns.2.name: "salary_change" }
+  - match: { columns.3.name: "salary_change_long" }
+  - match: { columns.4.name: "name" }
+  - length: { values: 1 }
+  - match: { values.0.0: "2021-01-01T00:00:00.000Z" }
+  - match: { values.0.1: 60000 }
+  - match: { values.0.2: 200.5 }
+  - match: { values.0.3: 200 }
+  - match: { values.0.4: "Bob Johnson" }
+
+---
+
+Foldable query using QSTR on name but with non-foldable expression:
+  - do:
+      catch: bad_request
+      esql.query:
+        body:
+          query: |
+            FROM employees
+            | WHERE QSTR(CONCAT(name, "Bob"))
+            | KEEP hire_date, salary, salary_change, salary_change_long, name
+            | LIMIT 5
+  - match: { error.type: "verification_exception" }
+  - contains: { error.reason: "Query must be a valid string in [QSTR(CONCAT(name, \"Bob\"))], found [CONCAT(name, \"Bob\")]" }
+