JingsongLi commented on code in PR #1164:
URL: https://github.com/apache/paimon-rust/pull/1164#discussion_r4386106715
##########
crates/paimon/src/table/kv_file_reader.rs:
##########
@@ -711,6 +761,56 @@ impl KeyValueFileReader {
.map(|budget| Arc::new(budget.without_prefetch()))
};
let mut file_streams: Vec<ArrowRecordBatchStream> =
Vec::new();
+ // One sorted run never repeats a key, so under these
engines
+ // every key is a lone version and needs no merge. Retract
+ // rows are still dropped per batch below: older Rust
writers
+ // recorded `delete_row_count = 0` for files holding them.
+ let mut skip_merge = skip_single_runs
+ && input_stream_count == 1
+ && matches!(
+ config.merge_engine,
+ MergeEngine::Deduplicate | MergeEngine::FirstRow
+ );
+ // A file written under another engine may hold several
+ // versions of a key (the aggregation writer kept them
before
+ // #839), and ALTER can switch the engine afterwards.
+ if skip_merge {
+ 'files: for run in &merge_group {
+ for file in &run.files {
+ // Always check the stored schema: dynamic
options and
+ // time travel can change the read schema's
engine
+ // without changing its ID. Merging is always
correct,
+ // so a missing schema file under the read
schema's ID
+ // only costs the skip.
+ let schema = match config
+ .schema_manager
+ .schema(file.file.schema_id)
+ .await
+ {
+ Ok(schema) => schema,
+ Err(crate::Error::IoUnexpected { source,
.. })
+ if source.kind() ==
opendal::ErrorKind::NotFound
+ && file.file.schema_id ==
table_schema_id =>
+ {
+ skip_merge = false;
+ break 'files;
+ }
+ Err(err) => Err(err)?,
+ };
+ let engine =
Review Comment:
[P2] Do not treat the stored engine as writer provenance
A persisted deduplicate schema can still own legacy files written with
aggregation. Before #839, public `Table::copy_with_options` allowed
`merge-engine=aggregation` plus `fields.value.aggregate-function=sum` without
changing the schema ID; `TableWrite` passed that overridden engine and original
ID to a writer whose aggregation flush retained every same-key version. This
check reads only the stored deduplicate engine and enables the shortcut for
those files. I reproduced the legitimate historical layout through public
commit/scan/read APIs: one two-file non-raw split contains (1,seq0,10),
(1,seq1,11) and disjoint key 2. This head emits both key-1 rows; exact base
370428b0 returns only (1,11). The aggregation control correctly returns (1,21).
Please retain duplicate collapsing for legacy files lacking a durable
uniqueness guarantee; schema options alone cannot establish which dynamic write
options produced them. Cover the historical write-side override as well as the
existing read-
side override cases.
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