(datafusion) 01/01: docs: mention output_rows_skew on partitioned operators in explain-usage (#26048)

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github-merge-queue[bot] pushed a commit to branch gh-readonly-queue/main/pr-26048-982fca6907fcfc12051fe64b989f3e708459a133
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commit 9f81b78aadafced613c09e730312aa1f390039d9
Author: Lía Adriana <li...@datadoghq.com>
AuthorDate: Mon Oct 5 10:02:53 2026 +0000

    docs: mention output_rows_skew on partitioned operators in explain-usage (#26048)
    
    Follow-up to #25977.
    
    ## Which issue does this PR close?
    
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    - Closes #.
    
    ## Rationale for this change
    
    now output_rows_skew is used in other operators than DataSourceExec, but
    I forgot to add it to the doc
    
    ## What changes are included in this PR?
    
    Small comment in the doc mentioning output_rows_skew is also used for
    other operators than DataSourceExec(parquet)
    
    ## What is the testing strategy for this PR?
    
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    ## Are there any user-facing changes?
    
    Just doc.
---
 docs/source/user-guide/explain-usage.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/docs/source/user-guide/explain-usage.md b/docs/source/user-guide/explain-usage.md
index 6654ca3e92..83ff5c3e54 100644
--- a/docs/source/user-guide/explain-usage.md
+++ b/docs/source/user-guide/explain-usage.md
@@ -243,6 +243,12 @@ When predicate pushdown is enabled, `DataSourceExec` with `ParquetSource` gains
 - `row_pushdown_eval_time`: time spent evaluating row-level filters
 - `page_index_eval_time`: time required to evaluate the page index filters
 
+`output_rows_skew` is also reported by operators that execute in multiple
+partitions: `RepartitionExec`, `HashJoinExec`, `AggregateExec`,
+`BoundedWindowAggExec` and `WindowAggExec`. It shows how evenly their output
+rows are spread across partitions, which helps spot data skew (for example, a
+hot join or grouping key). With a single partition the skew is always `0%`.
+
 ## Postgres-style `EXPLAIN (...)` options
 
 In addition to the legacy keyword form (`EXPLAIN ANALYZE VERBOSE FORMAT tree SELECT ...`),


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