Check k is a constant

Author: carlosdelest

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/vector/Knn.java

@@ -50,6 +50,7 @@
 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.ParamOrdinal.THIRD;
+import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isFoldable;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isMapExpression;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isNotNull;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isNotNullAndFoldable;
@@ -180,8 +181,9 @@ private TypeResolution resolveQuery() {
     }
 
     private TypeResolution resolveK() {
-        return isNotNull(k(), sourceText(), TypeResolutions.ParamOrdinal.THIRD)
-            .and(isType(k(), dt -> dt == INTEGER, sourceText(), TypeResolutions.ParamOrdinal.THIRD, "integer"));
+        return isType(k(), dt -> dt == INTEGER, sourceText(), THIRD, "integer")
+            .and(isFoldable(k(), sourceText(), THIRD))
+            .and(isNotNull(k(), sourceText(), THIRD));
     }
 
     private TypeResolution resolveOptions() {

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/analysis/VerifierTests.java

@@ -2173,24 +2173,25 @@ private void checkFullTextFunctionNullArgs(String functionInvocation, String arg
         );
     }
 
-    public void testFullTextFunctionsConstantQuery() throws Exception {
-        checkFullTextFunctionsConstantQuery("match(title, category)", "second");
-        checkFullTextFunctionsConstantQuery("qstr(title)", "");
-        checkFullTextFunctionsConstantQuery("kql(title)", "");
-        checkFullTextFunctionsConstantQuery("match_phrase(title, tags)", "second");
+    public void testFullTextFunctionsConstantArg() throws Exception {
+        checkFullTextFunctionsConstantArg("match(title, category)", "second");
+        checkFullTextFunctionsConstantArg("qstr(title)", "");
+        checkFullTextFunctionsConstantArg("kql(title)", "");
+        checkFullTextFunctionsConstantArg("match_phrase(title, tags)", "second");
         if (EsqlCapabilities.Cap.MULTI_MATCH_FUNCTION.isEnabled()) {
-            checkFullTextFunctionsConstantQuery("multi_match(category, body)", "first");
-            checkFullTextFunctionsConstantQuery("multi_match(concat(title, \"world\"), title)", "first");
+            checkFullTextFunctionsConstantArg("multi_match(category, body)", "first");
+            checkFullTextFunctionsConstantArg("multi_match(concat(title, \"world\"), title)", "first");
         }
         if (EsqlCapabilities.Cap.TERM_FUNCTION.isEnabled()) {
-            checkFullTextFunctionsConstantQuery("term(title, tags)", "second");
+            checkFullTextFunctionsConstantArg("term(title, tags)", "second");
         }
         if (EsqlCapabilities.Cap.KNN_FUNCTION.isEnabled()) {
-            checkFullTextFunctionsConstantQuery("knn(vector, vector, 10)", "second");
+            checkFullTextFunctionsConstantArg("knn(vector, vector, 10)", "second");
+            checkFullTextFunctionsConstantArg("knn(vector, [0, 1, 2], category)", "third");
         }
     }
 
-    private void checkFullTextFunctionsConstantQuery(String functionInvocation, String argOrdinal) throws Exception {
+    private void checkFullTextFunctionsConstantArg(String functionInvocation, String argOrdinal) throws Exception {
         assertThat(
             error("from test | where " + functionInvocation, fullTextAnalyzer),
             containsString(argOrdinal + " argument of [" + functionInvocation + "] must be a constant")