feat(cubesql): Support %s in format (#9129)

Used by Metabase introspection
See metabase/metabase#50900

Fixes #9126

Author: mcheshkov

rust/cubesql/cubesql/src/compile/engine/udf/common.rs

@@ -3281,6 +3281,42 @@ pub fn create_format_udf() -> ScalarUDF {
                         // %% is escaped to single %
                         result.push('%');
                     }
+                    Some('s') => {
+                        // Handle %s - regular string
+                        if arg_index >= args.len() {
+                            return Err(DataFusionError::Execution(
+                                "Not enough arguments for format string".to_string(),
+                            ));
+                        }
+
+                        let arg = &args[arg_index];
+                        let value = match arg.data_type() {
+                            DataType::Utf8 => {
+                                let str_arr = downcast_string_arg!(arg, "arg", i32);
+                                if str_arr.is_null(i) {
+                                    // A null value is treated as an empty string
+                                    String::new()
+                                } else {
+                                    str_arr.value(i).to_string()
+                                }
+                            }
+                            _ => {
+                                // For other types, try to convert to string
+                                let str_arr = cast(&arg, &DataType::Utf8)?;
+                                let str_arr =
+                                    str_arr.as_any().downcast_ref::<StringArray>().unwrap();
+                                if str_arr.is_null(i) {
+                                    // A null value is treated as an empty string
+                                    String::new()
+                                } else {
+                                    str_arr.value(i).to_string()
+                                }
+                            }
+                        };
+
+                        result.push_str(&value);
+                        arg_index += 1;
+                    }
                     Some(c) => {
                         return Err(DataFusionError::Execution(format!(
                             "Unsupported format specifier %{}",

rust/cubesql/cubesql/src/compile/mod.rs

@@ -16214,6 +16214,30 @@ LIMIT {{ limit }}{% endif %}"#.to_string(),
 
     #[tokio::test]
     async fn test_format_function() -> Result<(), CubeError> {
+        // Test: Basic usage with a single string
+        let result = execute_query(
+            "SELECT format('%s', 'foo') AS formatted_string".to_string(),
+            DatabaseProtocol::PostgreSQL,
+        )
+        .await?;
+        insta::assert_snapshot!("formatted_string", result);
+
+        // Test: Basic usage with a single null string
+        let result = execute_query(
+            "SELECT format('%s', NULL) = '' AS formatted_null_string_is_empty".to_string(),
+            DatabaseProtocol::PostgreSQL,
+        )
+        .await?;
+        insta::assert_snapshot!("formatted_null_string_is_empty", result);
+
+        // Test: Basic usage with a multiple strings
+        let result = execute_query(
+            "SELECT format('%s.%s', 'foo', 'bar') AS formatted_strings".to_string(),
+            DatabaseProtocol::PostgreSQL,
+        )
+        .await?;
+        insta::assert_snapshot!("formatted_strings", result);
+
         // Test: Basic usage with a single identifier
         let result = execute_query(
             "SELECT format('%I', 'column_name') AS formatted_identifier".to_string(),

rust/cubesql/cubesql/src/compile/snapshots/cubesql__compile__tests__formatted_null_string_is_empty.snap

@@ -0,0 +1,9 @@
+---
+source: cubesql/src/compile/mod.rs
+expression: result
+---
++--------------------------------+
+| formatted_null_string_is_empty |
++--------------------------------+
+| true                           |
++--------------------------------+

rust/cubesql/cubesql/src/compile/snapshots/cubesql__compile__tests__formatted_string.snap

@@ -0,0 +1,9 @@
+---
+source: cubesql/src/compile/mod.rs
+expression: result
+---
++------------------+
+| formatted_string |
++------------------+
+| foo              |
++------------------+

rust/cubesql/cubesql/src/compile/snapshots/cubesql__compile__tests__formatted_strings.snap

@@ -0,0 +1,9 @@
+---
+source: cubesql/src/compile/mod.rs
+expression: result
+---
++-------------------+
+| formatted_strings |
++-------------------+
+| foo.bar           |
++-------------------+