dejankrak-db opened a new pull request, #56239:
URL: https://github.com/apache/spark/pull/56239
### What changes were proposed in this pull request?
A parameterless built-in function (`current_user`, `current_date`,
`current_time`, `current_timestamp`, `user`, `session_user`, `grouping__id`)
now takes precedence over a SQL UDF parameter that shares its name. Previously
the UDF parameter alias shadowed the built-in, e.g. `CREATE FUNCTION
f(current_user STRING) RETURNS STRING RETURN current_user; SELECT f('alice')`
returned `'alice'` instead of the actual current user.
SQL UDF input-parameter aliases are marked with a named `Metadata` key,
`SessionCatalog.SQL_FUNCTION_PARAMETER_ALIAS_METADATA_KEY`. Producers are
`SessionCatalog.makeSQLFunctionPlan` and `makeSQLTableFunctionPlan` (CALL time,
scalar and table UDFs) and `CreateSQLFunctionCommand` (CREATE time). Storing
the marker in `Metadata` (rather than a `TreeNodeTag`) lets it propagate
automatically through `Alias.toAttribute` and `AttributeReference` copies.
In `ColumnResolutionHelper`, when name-based resolution returns an attribute
carrying this metadata, `LiteralFunctionResolution` is preferred over it. Real
columns from relations (no marker) still win, preserving the overall precedence
(column > parameterless function > UDF parameter).
The new behavior is gated behind a legacy kill-switch,
`spark.sql.legacy.allowUdfParameterToShadowParameterlessFunction` (default
`false`); set to `true` to restore the previous behavior.
### Why are the changes needed?
To match the documented SQL name resolution rules: a parameterless built-in
function should not be shadowed by a same-named UDF parameter.
### Does this PR introduce _any_ user-facing change?
Yes. A SQL UDF parameter named like a parameterless built-in function no
longer shadows that function in the function body. The legacy conf restores the
old behavior.
### How was this patch tested?
Added golden-file tests `sql-udf-name-precedence(.legacy)` and
`parameterless-function-name-precedence(.legacy)` covering column > param, LCA
> param, outer-ref > param, parameterless function > param (scalar and table
UDF), param > session variable, nested-UDF inner-scope binding, and the legacy
(flag-on) behavior. All 4 scenarios pass.
### Was this patch authored or co-authored using generative AI tooling?
Yes, co-authored using Claude code.
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