Cannot alias current_timestamp to "current_timestamp"

[jonathanswenson]

What happens?

Little strange here, but noticed this broke with the 1.1.0 -> 1.1.1 change, using the current_timestamp keyword aliased to "current_timestamp" throws an error

on v1.1.1 af39bd0dcf

D select current_timestamp as "current_timestamp";
Binder Error: Column "current_timestamp" referenced that exists in the SELECT clause - but this column cannot be referenced before it is defined

on v1.1.0 fa5c2fe15f

D select current_timestamp as "current_timestamp";
┌────────────────────────────┐
│     current_timestamp      │
│  timestamp with time zone  │
├────────────────────────────┤
│ 2024-10-08 09:07:08.335-07 │
└────────────────────────────┘

Notably postgres allows this:

test=# select current_timestamp as "current_timestamp";
       current_timestamp       
-------------------------------
 2024-10-08 16:04:24.472592+00
(1 row)

To Reproduce

select current_timestamp as "current_timestamp";

OS:

MacOS 14.5 aarch64

DuckDB Version:

1.1.1

DuckDB Client:

cli

Hardware:

No response

Full Name:

Jonathan Swenson

Affiliation:

Omni

What is the latest build you tested with? If possible, we recommend testing with the latest nightly build.

I have tested with a stable release

Did you include all relevant data sets for reproducing the issue?

Not applicable - the reproduction does not require a data set

Did you include all code required to reproduce the issue?

• [X] Yes, I have

Did you include all relevant configuration (e.g., CPU architecture, Python version, Linux distribution) to reproduce the issue?

• [X] Yes, I have

[jonathanswenson]

Somewhat reminiscent of https://github.com/duckdb/duckdb/issues/12646

[zmajeed]

This bug affects all SQL value functions like current_timestamp including current_time, current_date, current_user - when the alias is the function name itself. It's caused by https://github.com/duckdb/duckdb/pull/13925

A column is bound in ExpressionBinder::BindExpression - https://github.com/duckdb/duckdb/blob/main/src/planner/binder/expression/bind_columnref_expression.cpp

432 // column was not found - check if it is a SQL value function
433 auto value_function = GetSQLValueFunction(col_ref_p.GetColumnName());
434 if (value_function) {
435   return BindExpression(value_function, depth);

But GetSQLValueFunction - https://github.com/duckdb/duckdb/blob/main/src/planner/expression_binder/select_binder.cpp - only returns a value function if the name is not an alias

With no value function to bind to the column, control goes to SelectBinder::BindColumnRef - https://github.com/duckdb/duckdb/blob/main/src/planner/expression_binder/select_binder.cpp - where binding to the alias is attempted but fails because the index of the column for the alias is past any valid boundcolumn index - because the column hasn't been bound yet

26 // binding failed
27 // check in the alias map
28 auto &colref = (expr_ptr.get())->Cast<ColumnRefExpression>();
29 if (!colref.IsQualified()) {
30   auto &bind_state = node.bind_state;
31   auto alias_entry = node.bind_state.alias_map.find(colref.column_names[0]);
32   if (alias_entry != node.bind_state.alias_map.end()) {
33     // found entry!
34     auto index = alias_entry->second;
35     if (index >= node.bound_column_count) {
36       throw BinderException("Column \"%s\" referenced that exists in the SELECT clause - but this column "
37         "cannot be referenced before it is defined",
38         colref.column_names[0]);
39     }

[zmajeed]

It seems GetSQLValueFunction shouldn't fail - this could be done by skipping the alias check if the actual column name - not the passed string - is aliased to itself

Something like GetSQLValueFunction(const ColumnRefExpression& column) could do this

I can open a PR if this looks reasonable