apache · andygrove · Mar 20, 2026 · Mar 20, 2026 · Mar 20, 2026 · Mar 20, 2026
diff --git a/docs/source/user-guide/latest/expressions.md b/docs/source/user-guide/latest/expressions.md
@@ -90,6 +90,12 @@ Expressions that are not Spark-compatible will fall back to Spark by default and
 | Substring       | Yes               |                                                                                                            |
 | Upper           | No                | Results can vary depending on locale and character set. Requires `spark.comet.caseConversion.enabled=true` |
 
+## JSON Functions
+
+| Expression    | Spark-Compatible? | Compatibility Notes                                                                           |
+| ------------- | ----------------- | --------------------------------------------------------------------------------------------- |
+| GetJsonObject | No                | Spark allows single-quoted JSON and unescaped control characters which Comet does not support |
+
 ## Date/Time Functions
 
 | Expression     | SQL                          | Spark-Compatible? | Compatibility Notes                                                                                                              |

diff --git a/docs/spark_expressions_support.md b/docs/spark_expressions_support.md
@@ -245,7 +245,7 @@
 ### json_funcs
 
 - [ ] from_json
-- [ ] get_json_object
+- [x] get_json_object
 - [ ] json_array_length
 - [ ] json_object_keys
 - [ ] json_tuple

diff --git a/native/Cargo.lock b/native/Cargo.lock
diff --git a/native/spark-expr/Cargo.toml b/native/spark-expr/Cargo.toml
@@ -34,7 +34,8 @@ chrono-tz = { workspace = true }
 num = { workspace = true }
 regex = { workspace = true }
 serde = { version = "1.0", features = ["derive"] }
-serde_json = "1.0"
+# preserve_order: needed for get_json_object to match Spark's JSON key ordering
+serde_json = { version = "1.0", features = ["preserve_order"] }
 thiserror = { workspace = true }
 futures = { workspace = true }
 twox-hash = "2.1.2"

diff --git a/native/spark-expr/src/comet_scalar_funcs.rs b/native/spark-expr/src/comet_scalar_funcs.rs
@@ -181,6 +181,10 @@ pub fn create_comet_physical_fun_with_eval_mode(
             let func = Arc::new(crate::string_funcs::spark_split);
             make_comet_scalar_udf!("split", func, without data_type)
         }
+        "get_json_object" => {
+            let func = Arc::new(crate::string_funcs::spark_get_json_object);
+            make_comet_scalar_udf!("get_json_object", func, without data_type)
+        }
         _ => registry.udf(fun_name).map_err(|e| {
             DataFusionError::Execution(format!(
                 "Function {fun_name} not found in the registry: {e}",