[I] [Improvement][rust] Align fixed-schema log reads by column ID [fluss]

["slfan1989 (via GitHub)" <gi...@apache.org>]

slfan1989 opened a new issue, #3770:
URL: https://github.com/apache/fluss/issues/3770

   ### Search before asking
   
   - [x] I searched in the [issues](https://github.com/apache/fluss/issues) and found nothing similar.
   
   
   ### Motivation
   
   ### Motivation
   
   The Rust fixed-schema log scanner currently aligns historical Arrow batches with the scanner schema by Arrow field name.
   
   This differs from the KV `FixedSchemaDecoder`, which uses stable Fluss column IDs through `index_mapping`.
   
   Name-based alignment is not robust for schema evolution:
   
   - A column with the same ID but a different name may be treated as missing.
   - A newly added column that reuses an old column name but has a different ID
     may incorrectly read the old column value.
   
   Although the Fluss server does not currently support `RENAME COLUMN`, the Rust fixed-schema decoding path should consistently use column IDs as the stable column identity.
   
   ### Solution
   
   Use Fluss column IDs when aligning historical Arrow batches with the fixed target schema:
   
   - Preserve values when the source and target columns have the same ID.
   - Fill the target column with NULL when its ID does not exist in the source
     schema.
   - Do not match columns that only have the same name but different IDs.
   - Apply the same behavior to local and remote log reads.
   - Reuse the existing `index_mapping` logic used by `FixedSchemaDecoder`.
   
   ### Anything else?
   
   This improvement does not change the public API or storage format.
   
   ### Willingness to contribute
   
   - [x] I'm willing to submit a PR!


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Re: [I] [Improvement][rust] Align fixed-schema log reads by column ID [fluss]

["fresh-borzoni (via GitHub)" <gi...@apache.org>]

fresh-borzoni closed issue #3770: [Improvement][rust] Align fixed-schema log reads by column ID
URL: https://github.com/apache/fluss/issues/3770


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