[GitHub] [arrow] sunchao commented on a change in pull request #7917: ARROW-8243: [Rust] [Parquet] Serialize Arrow schema metadata

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

sunchao commented on a change in pull request #7917:
URL: https://github.com/apache/arrow/pull/7917#discussion_r470327828



##########
File path: rust/parquet/src/file/properties.rs
##########
@@ -99,7 +99,7 @@ pub struct WriterProperties {
     max_row_group_size: usize,
     writer_version: WriterVersion,
     created_by: String,
-    key_value_metadata: Option<Vec<KeyValue>>,
+    pub(crate) key_value_metadata: Option<Vec<KeyValue>>,

Review comment:
       +1. I think this is fine.

##########
File path: rust/parquet/Cargo.toml
##########
@@ -52,4 +53,4 @@ zstd = "0.5"
 arrow = { path = "../arrow", version = "2.0.0-SNAPSHOT" }
 
 [features]
-default = ["arrow", "snap", "brotli", "flate2", "lz4", "zstd"]
+default = ["arrow", "snap", "brotli", "flate2", "lz4", "zstd", "base64"]

Review comment:
       Sounds fine. What will the be error message like in this case?

##########
File path: rust/parquet/src/arrow/schema.rs
##########
@@ -55,40 +55,75 @@ pub fn parquet_to_arrow_schema_by_columns<T>(
 where
     T: IntoIterator<Item = usize>,
 {
-    let mut base_nodes = Vec::new();
-    let mut base_nodes_set = HashSet::new();
-    let mut leaves = HashSet::new();
-
-    for c in column_indices {
-        let column = parquet_schema.column(c).self_type() as *const Type;
-        let root = parquet_schema.get_column_root(c);
-        let root_raw_ptr = root as *const Type;
-
-        leaves.insert(column);
-        if !base_nodes_set.contains(&root_raw_ptr) {
-            base_nodes.push(root);
-            base_nodes_set.insert(root_raw_ptr);
+    let mut metadata = parse_key_value_metadata(key_value_metadata).unwrap_or_default();

Review comment:
       👍 




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