You are viewing a plain text version of this content. The canonical link for it is here.

Posted to reviews@spark.apache.org by "dtenedor (via GitHub)" <gi...@apache.org> on 2025/11/10 22:55:16 UTC

[PR] [SPARK-51518][SQL] Support | as an alternative to |> for the SQL pipe operator token [spark]

dtenedor opened a new pull request, #52983:
URL: https://github.com/apache/spark/pull/52983

   ### What changes were proposed in this pull request?
   
   This PR adds support for `|` as an alternative to `|>` for the SQL pipe operator token, while maintaining full backwards compatibility with existing bitwise OR operations.
   
   For example, this is now supported:
   
   ```sql
   table t
   | select x, y
   | where x < 2;
   ```
   
   as an alternative to:
   
   ```sql
   table t
   |> select x, y
   |> where x < 2;
   ```
   
   The implementation uses a semantic predicate with 2-token lookahead (`isOperatorPipeStart()`) to disambiguate between:
   - **Pipe operators**: When `|` is followed by keywords like `SELECT`, `WHERE`, `EXTEND`, `JOIN`, etc.
   - **Bitwise OR**: When `|` is part of an expression (e.g., `col1 | col2`)
   
   This approach ensures that existing SQL queries using `|` for bitwise OR operations continue to work without any changes, including edge cases where column names match pipe operator keywords (e.g., `col1 | select` where `select` is a column name).
   
   ### Why are the changes needed?
   
   This provides syntax compatibility with other languages that use `|` for pipe operations, such as:
   - Splunk SPL
   - Kusto (KQL)
   - Unix shell pipes
   
   **Background:**
   
   We previously attempted this in https://github.com/apache/spark/pull/50284 but abandoned that approach because it inadvertently broke bitwise OR expression usage. After further investigation, we've developed a solution using ANTLR semantic predicates that properly disambiguates the two contexts.
   
   As discussed in that PR:
   - Jeff Shute (author of the SQL pipe syntax paper from Google) confirmed that Google uses an LALR parser which makes it impossible for them to support `|` due to ambiguity with bitwise operations
   - There is growing industry consensus that `|>` should be the primary/universal token, but engines may optionally support additional tokens
   - This approach aligns with how other databases have addressed this (see https://superdb.org/docs/language/pipe-ambiguity/)
   
   Spark's use of ANTLR (not LALR) enables us to support both tokens through lookahead-based disambiguation.
   
   ### Does this PR introduce _any_ user-facing change?
   
   Yes, users can now use `|` as a more concise alternative to `|>` for pipe operators.
   
   **This change is fully backwards-compatible:**
   - All existing queries using `|>` continue to work
   - All existing queries using `|` for bitwise OR continue to work
   - Users can even mix `|` and `|>` in the same query
   
   ### How was this patch tested?
   
   This PR includes comprehensive test coverage in `pipe-operators.sql`:
   
   **Positive tests:** All pipe operator types using `|` syntax:
   - SELECT, EXTEND, SET, DROP, AS, WHERE
   - PIVOT, UNPIVOT, TABLESAMPLE
   - JOIN (all types: inner, cross, left, right, full, semi, anti, lateral, natural)
   - Set operations (UNION, EXCEPT, INTERSECT, MINUS)
   - ORDER BY, LIMIT, OFFSET, DISTRIBUTE BY, CLUSTER BY
   - AGGREGATE, WINDOW
   - Chained operations with multiple pipe operators
   - Mixed `|` and `|>` syntax in the same query
   
   **Negative tests (backwards compatibility):** Bitwise OR operations with keyword column names:
   - Tested bitwise OR with columns named: `select`, `extend`, `set`, `drop`, `as`, `where`, `order`, `limit`, `aggregate`, `window`, `pivot`, `unpivot`, `join`, `union`, `intersect`, `except`
   - Complex bitwise OR expressions: `(col1 | select) + (where | order)`
   - Multiple bitwise OR chains: `col1 | select | where | order`
   - Bitwise OR in WHERE clauses: `where (col1 | select) > 2`
   
   All tests pass successfully.
   
   ### Was this patch authored or co-authored using generative AI tooling?
   
   Yes, `claude-4.5-sonnet` with manual review and editing.


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org


---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org