[GitHub] [arrow] jorgecarleitao commented on a change in pull request #8033: ARROW-9837: [Rust][DataFusion] Add provider for variable

[GitBox <gi...@apache.org>]

jorgecarleitao commented on a change in pull request #8033:
URL: https://github.com/apache/arrow/pull/8033#discussion_r475270454



##########
File path: rust/datafusion/src/variable/system.rs
##########
@@ -0,0 +1,18 @@
+use crate::logicalplan::ScalarValue;
+use crate::error::Result;
+use crate::variable::VariableProvider;
+
+pub struct SystemVariable {}
+
+impl SystemVariable {
+    pub fn new() -> Self {
+        Self {}
+    }
+}
+
+impl VariableProvider for SystemVariable {
+    fn get_value(&self, variable_names: Vec<String>) -> Result<ScalarValue> {
+        let s = format!("{}-{}", "test".to_string(), variable_names.concat());

Review comment:
       why `test`?




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