iffyio commented on code in PR #1467:
URL:
https://github.com/apache/datafusion-sqlparser-rs/pull/1467#discussion_r1798046143
##########
src/parser/mod.rs:
##########
@@ -11173,15 +11173,42 @@ impl<'a> Parser<'a> {
self.peek_token().location
)
}
- expr => self
- .parse_optional_alias(keywords::RESERVED_FOR_COLUMN_ALIAS)
- .map(|alias| match alias {
- Some(alias) => SelectItem::ExprWithAlias { expr, alias },
- None => SelectItem::UnnamedExpr(expr),
- }),
+ expr => {
+ if dialect_of!(self is MsSqlDialect) {
Review Comment:
We recently started to discourage the use of
[dialect_of](https://github.com/apache/datafusion-sqlparser-rs/blob/383226c3e81d9e5ed64f6f188815dfc9d7fea317/src/dialect/mod.rs#L63-L72)
can we update this to use a method on the Dialect trait as described in the
link?
We could add a method like `supports_eq_alias_assigment` or similar
##########
src/parser/mod.rs:
##########
@@ -11173,15 +11173,42 @@ impl<'a> Parser<'a> {
self.peek_token().location
)
}
- expr => self
- .parse_optional_alias(keywords::RESERVED_FOR_COLUMN_ALIAS)
- .map(|alias| match alias {
- Some(alias) => SelectItem::ExprWithAlias { expr, alias },
- None => SelectItem::UnnamedExpr(expr),
- }),
+ expr => {
+ if dialect_of!(self is MsSqlDialect) {
+ if let Some(select_item) =
self.parse_mssql_alias_with_equal(&expr) {
+ return Ok(select_item);
+ }
+ }
+ self.parse_optional_alias(keywords::RESERVED_FOR_COLUMN_ALIAS)
+ .map(|alias| match alias {
+ Some(alias) => SelectItem::ExprWithAlias { expr, alias
},
+ None => SelectItem::UnnamedExpr(expr),
+ })
+ }
}
}
+ /// Parse a [`SelectItem`] based on an MsSql syntax that uses the equal
sign
+ /// to denote an alias, for example: SELECT col_alias = col FROM tbl
+ ///
<https://learn.microsoft.com/en-us/sql/t-sql/queries/select-examples-transact-sql?view=sql-server-ver16#b-use-select-with-column-headings-and-calculations>
Review Comment:
```suggestion
/// Parse a [`SelectItem`] based on an [MsSql] syntax that uses the
equal sign
/// to denote an alias, for example: SELECT col_alias = col FROM tbl
/// [MsSql]:
https://learn.microsoft.com/en-us/sql/t-sql/queries/select-examples-transact-sql?view=sql-server-ver16#b-use-select-with-column-headings-and-calculations
```
##########
src/parser/mod.rs:
##########
@@ -11173,15 +11173,42 @@ impl<'a> Parser<'a> {
self.peek_token().location
)
}
- expr => self
- .parse_optional_alias(keywords::RESERVED_FOR_COLUMN_ALIAS)
- .map(|alias| match alias {
- Some(alias) => SelectItem::ExprWithAlias { expr, alias },
- None => SelectItem::UnnamedExpr(expr),
- }),
+ expr => {
+ if dialect_of!(self is MsSqlDialect) {
+ if let Some(select_item) =
self.parse_mssql_alias_with_equal(&expr) {
+ return Ok(select_item);
+ }
+ }
+ self.parse_optional_alias(keywords::RESERVED_FOR_COLUMN_ALIAS)
+ .map(|alias| match alias {
+ Some(alias) => SelectItem::ExprWithAlias { expr, alias
},
+ None => SelectItem::UnnamedExpr(expr),
+ })
+ }
}
}
+ /// Parse a [`SelectItem`] based on an MsSql syntax that uses the equal
sign
+ /// to denote an alias, for example: SELECT col_alias = col FROM tbl
+ ///
<https://learn.microsoft.com/en-us/sql/t-sql/queries/select-examples-transact-sql?view=sql-server-ver16#b-use-select-with-column-headings-and-calculations>
+ fn parse_mssql_alias_with_equal(&mut self, expr: &Expr) ->
Option<SelectItem> {
+ if let Expr::BinaryOp {
+ left, op, right, ..
+ } = expr
+ {
+ if op == &BinaryOperator::Eq {
+ if let Expr::Identifier(ref alias) = **left {
+ return Some(SelectItem::ExprWithAlias {
+ expr: *right.clone(),
+ alias: alias.clone(),
+ });
+ }
+ }
+ }
+
+ None
Review Comment:
```suggestion
if let Expr::BinaryOp {
left: Expr::Identifier(alias), op: BinaryOperator::Eq, right,
} = expr {
SelectItem::ExprWithAlias {
expr: right,
alias: Expr::Identifier(alias),
}
} else {
expr
}
```
Could be simplified to the following? I think no need to pass in a reference
and return an option, we can move the value and return the same value if
untouched?
Also we can skip the `..` operator when deconstructing in this case, so that
if the field set changes, we would be notified to ensure the logic remains
correct.
##########
src/parser/mod.rs:
##########
@@ -11173,15 +11173,42 @@ impl<'a> Parser<'a> {
self.peek_token().location
)
}
- expr => self
- .parse_optional_alias(keywords::RESERVED_FOR_COLUMN_ALIAS)
- .map(|alias| match alias {
- Some(alias) => SelectItem::ExprWithAlias { expr, alias },
- None => SelectItem::UnnamedExpr(expr),
- }),
+ expr => {
+ if dialect_of!(self is MsSqlDialect) {
+ if let Some(select_item) =
self.parse_mssql_alias_with_equal(&expr) {
+ return Ok(select_item);
+ }
+ }
+ self.parse_optional_alias(keywords::RESERVED_FOR_COLUMN_ALIAS)
+ .map(|alias| match alias {
+ Some(alias) => SelectItem::ExprWithAlias { expr, alias
},
+ None => SelectItem::UnnamedExpr(expr),
+ })
+ }
}
}
+ /// Parse a [`SelectItem`] based on an MsSql syntax that uses the equal
sign
+ /// to denote an alias, for example: SELECT col_alias = col FROM tbl
+ ///
<https://learn.microsoft.com/en-us/sql/t-sql/queries/select-examples-transact-sql?view=sql-server-ver16#b-use-select-with-column-headings-and-calculations>
+ fn parse_mssql_alias_with_equal(&mut self, expr: &Expr) ->
Option<SelectItem> {
Review Comment:
```suggestion
fn maybe_unpack_alias_assignment(expr: &Expr) -> Option<SelectItem> {
```
Thinking since this is only a helper function that it doesn't get confused
for a parser/parsing method
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