[GitHub] [arrow-datafusion] mingmwang commented on a diff in pull request #4347: Do not error in optimizer if resulting schema has different metadata

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

mingmwang commented on code in PR #4347:
URL: https://github.com/apache/arrow-datafusion/pull/4347#discussion_r1031012003


##########
datafusion/common/src/dfschema.rs:
##########
@@ -338,6 +338,24 @@ impl DFSchema {
             })
     }
 
+    /// Returns true if the two schemas have the same qualified named
+    /// fields with the same data types. Returns false otherwise.
+    ///
+    /// This is a specialized version of Eq that ignores differences
+    /// in nullability and metadata.
+    pub fn equivalent_names_and_types(&self, other: &Self) -> bool {
+        if self.fields().len() != other.fields().len() {
+            return false;
+        }
+        let self_fields = self.fields().iter();
+        let other_fields = other.fields().iter();
+        self_fields.zip(other_fields).all(|(f1, f2)| {
+            f1.qualifier() == f2.qualifier()
+                && f1.data_type() == f2.data_type()
+                && f1.name() == f2.name()
+        })
+    }
+

Review Comment:
   Some complex arrow types are nested types and can include other Fields.
   ````
       /// A list of some logical data type with variable length.
       List(Box<Field>),
       /// A list of some logical data type with fixed length.
       FixedSizeList(Box<Field>, i32),
       /// A list of some logical data type with variable length and 64-bit offsets.
       LargeList(Box<Field>),
       /// A nested datatype that contains a number of sub-fields.
       Struct(Vec<Field>),
   ````
   https://github.com/apache/arrow-rs/blob/cea5146b69b3413a1d5caa946e0774ec8d834e95/arrow-schema/src/datatype.rs#L163-L187



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