goldmedal commented on code in PR #11724:
URL: https://github.com/apache/datafusion/pull/11724#discussion_r1701979383
##########
datafusion/common/src/column.rs:
##########
@@ -372,7 +372,7 @@ impl FromStr for Column {
impl fmt::Display for Column {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- write!(f, "{}", self.flat_name())
+ write!(f, "{}", self.quoted_flat_name())
Review Comment:
> identifier could includes dot, that is the reason we need double quote to
differentiate it from qualified column. Identifier with dot is relatively rare
compare to column, so we don't have double quote every where.
>
Agreed. That makes sense to me. A `Column` comprises multiple identifiers:
`catalog.schema.table.column`. All the parts are `identifiers`. However,
because we don't have an `Expr` for an `Identifier`, I can only handle it for
`Column`. Currently, we represent an identifier as an unqualified column.
https://github.com/apache/datafusion/blob/0332eb569a5428ac385fe892ce7b5fb40d52c8c0/datafusion/expr/src/expr_fn.rs#L90-L92
Ideally, all of the `names` should be identifiers (e.g., table name, column
name, function name, or alias) that should be quoted if needed. This purpose
will impact many parts.
> I think only adding double quote for identifier that includes dot is
probably a better idea.
>
> If we have column that has name includes dot, we display it like
`qualifier."dot.column"`
I believe `quoted_flat_name()` that will invoke `quote_identifier` handles
this logic well.
https://github.com/apache/datafusion/blob/0332eb569a5428ac385fe892ce7b5fb40d52c8c0/datafusion/common/src/utils/mod.rs#L260-L280
This function doesn't always quote the identifier. Only quote it if it
contains invalid characters, such as a dot, bracket, or uppercase letter.
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