JeonDaehong commented on code in PR #1164:
URL: https://github.com/apache/paimon-rust/pull/1164#discussion_r4369392691
##########
crates/paimon/src/table/kv_file_reader.rs:
##########
@@ -711,6 +761,42 @@ 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 {
+ let schema_id = file.file.schema_id;
+ if schema_id == table_schema_id {
Review Comment:
Fixed in 9b8cd4b. The shortcut now only applies when `merge-engine` wasn't
set through dynamic options (`Table::merge_engine_overridden`). Otherwise the
file's stored schema is checked. Your `copy_with_options({"merge-engine":
"deduplicate"})` case is now a test,
`single_run_read_merges_when_options_override_the_engine`. It returns `[1, 1,
2]` without the fix.
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