[GitHub] [arrow-datafusion] Dandandan opened a new issue #279: Wrap unnamed expressions in alias, improve display unnamed expressions

[GitBox <gi...@apache.org>]

Dandandan opened a new issue #279:
URL: https://github.com/apache/arrow-datafusion/issues/279


   **Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
   To support optimizations like constant folding the column names need to keep consistent.
   
   This is already visible at the (limited) constant folding we have:
   ```
   > SELECT TRUE = TRUE;
   +---------------+
   | Boolean(true) |
   +---------------+
   | true          |
   +---------------+
   1 rows in set. Query took 0 seconds.
   ```
   
   Expected is `TRUE = TRUE` (PostgreSQL) or `Boolean(true) Eq Boolean(true)` (as is used currently).
   
   **Describe the solution you'd like**
   Wrap unnamed expressions in the original. This can be updated in the `sql_expr_to_logical_expr` function in the `/datafusion/src/sql/planner.rs`
   PostgreSQL keeps the original (textual) expression with original spacing - that seems currently not feasible as sqlparser is not lossy - but we can use the formatted representation of a `SQLExpr`.
   
   **Describe alternatives you've considered**
   Keep it as is - here the column names would changed based on the applied optimizations. This is however not consistent with PostgreSQL and other databases and confusing.
   
   **Additional context**
   https://github.com/apache/arrow-datafusion/issues/237


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