fix(highgo): preserve public functions in schema queries

Closes #5617

agents/drivers/highgo/src/main/java/com/dbx/agent/highgo/HighgoAgent.java

@@ -14,6 +14,14 @@ public final class HighgoAgent extends PostgresLikeAgent {
         super(HIGHGO_PROFILE);
     }
 
+    @Override
+    public String setSchemaSQL(String schema) {
+        if ("public".equals(schema)) {
+            return super.setSchemaSQL(schema);
+        }
+        return super.setSchemaSQL(schema) + ", public";
+    }
+
     public static void main(String[] args) {
         new MultiSessionJsonRpcServer(HighgoAgent::new).run();
     }

agents/drivers/highgo/src/test/java/com/dbx/agent/highgo/HighgoAgentTest.java

@@ -28,6 +28,15 @@ class HighgoAgentTest extends JdbcFakeExecutionBehaviorTest {
         Assertions.assertEquals("jdbc:highgo://{host}:{port}/{database}", agent.getProfile().getUrlTemplate());
     }
 
+    @Test
+    void preservesPublicFunctionsWhenSwitchingSchemas() {
+        HighgoAgent agent = new HighgoAgent();
+
+        Assertions.assertEquals("SET search_path TO \"app\", public", agent.setSchemaSQL("app"));
+        Assertions.assertEquals("SET search_path TO \"public\"", agent.setSchemaSQL("public"));
+        Assertions.assertEquals("SET search_path TO \"PUBLIC\", public", agent.setSchemaSQL("PUBLIC"));
+    }
+
     @Test
     void readsViewSourceWithQuotedRegclassParameter() {
         HighgoAgent agent = new HighgoAgent();