chore: use once_cell to avoid parse everytime in pipeline exec (#5943)

* chore: use once_cell to avoid parse everytime

* chore: remove pub on options

src/pipeline/src/etl/transform/transformer/greptime.rs

@@ -25,6 +25,7 @@ use api::v1::{ColumnDataType, ColumnDataTypeExtension, JsonTypeExtension, Semant
 use coerce::{coerce_columns, coerce_value};
 use greptime_proto::v1::{ColumnSchema, Row, Rows, Value as GreptimeValue};
 use itertools::Itertools;
+use once_cell::sync::OnceCell;
 use serde_json::Number;
 
 use crate::error::{
@@ -54,8 +55,12 @@ pub struct GreptimeTransformer {
 /// Parameters that can be used to configure the greptime pipelines.
 #[derive(Debug, Clone, Default)]
 pub struct GreptimePipelineParams {
-    /// The options for configuring the greptime pipelines.
-    pub options: HashMap<String, String>,
+    /// The original options for configuring the greptime pipelines.
+    /// This should not be used directly, instead, use the parsed shortcut option values.
+    options: HashMap<String, String>,
+
+    /// Parsed shortcut option values
+    pub flatten_json_object: OnceCell<bool>,
 }
 
 impl GreptimePipelineParams {
@@ -70,15 +75,20 @@ impl GreptimePipelineParams {
             .map(|(k, v)| (k.to_string(), v.to_string()))
             .collect::<HashMap<String, String>>();
 
-        Self { options }
+        Self {
+            options,
+            flatten_json_object: OnceCell::new(),
+        }
     }
 
     /// Whether to flatten the JSON object.
     pub fn flatten_json_object(&self) -> bool {
-        self.options
-            .get("flatten_json_object")
-            .map(|v| v == "true")
-            .unwrap_or(false)
+        *self.flatten_json_object.get_or_init(|| {
+            self.options
+                .get("flatten_json_object")
+                .map(|v| v == "true")
+                .unwrap_or(false)
+        })
     }
 }