Re: BUG #18327: Column naming inconsistency for boolean literals in ELSE clauses of CASE expressions. - Mailing list pgsql-bugs

From David G. Johnston
Subject Re: BUG #18327: Column naming inconsistency for boolean literals in ELSE clauses of CASE expressions.
Date
Msg-id CAKFQuwa6pmbdMDvjzkQijaimLwXXQYTGRReT-od0y-E42EjhxQ@mail.gmail.com
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In response to BUG #18327: Column naming inconsistency for boolean literals in ELSE clauses of CASE expressions.  (PG Bug reporting form <noreply@postgresql.org>)
Responses Re: BUG #18327: Column naming inconsistency for boolean literals in ELSE clauses of CASE expressions.
List pgsql-bugs
On Sun, Feb 4, 2024, 11:19 PG Bug reporting form <noreply@postgresql.org> wrote:
The following bug has been logged on the website:

Bug reference:      18327
Logged by:          Michael Bondarenko
Email address:      work.michael.2956@gmail.com
PostgreSQL version: 14.10
Operating system:   MacOS Sonoma 14.1.1 (23B81)
Description:       

I'm running my queries on the TPC-H schema, which can be found at:
https://github.com/dimitri/tpch-citus/blob/master/schema/tpch-schema.sql

I found the following inconsistency:

This one doesn't have a name to use.  Using case is better than picking one of the branches to make up a name from.



```
tpch=# select case when true then true else true end;
 case
------
 t
(1 row)

All of these do.  And in any case we never publish how we choose our aliases in this circumstance so it cannot be a bug.

The subquery forces a name to be chosen for the output relation.  Then since only one branch has a name to provide it is used.


tpch=# select case when true then true else (select true) end;
 bool
------
 t
(1 row)
```

As you can see, the auto-generated aliases do not correspond. The expected
behaviour was for the first query to also name the column 'bool'.

I base my expectations on:

1) This query naming the result 'bool':
```
tpch=# select true;
 bool
------
 t
(1 row)
```

2) These queries propagating the column name from the else clause of the
case expression:
2.1) Propagation of the aggregate function name
```
tpch=# select case when true then true else bool_or(true) end;
 bool_or
---------
 t
(1 row)
```


This is indeed all consistent in that literals don't have names while other expression tend to.

David J.

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