Support CONVERT expressions

[lovasoa]

fixes #1047

adds support for the following CONVERT syntaxes:

• CONVERT('héhé' USING utf8mb4) (MySQL, Postgres)
• CONVERT('héhé', CHAR CHARACTER SET utf8mb4) (MySQL)
• CONVERT(DECIMAL(10, 5), 42) (MSSQL) - the type comes first

[coveralls]

Pull Request Test Coverage Report for Build 6915102482

• 59 of 69 (85.51%) changed or added relevant lines in 7 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.007%) to 87.708%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/dialect/mod.rs	1	2	50.0%
src/dialect/mssql.rs	1	2	50.0%
src/dialect/redshift.rs	0	2	0.0%
src/ast/mod.rs	14	17	82.35%
src/parser/mod.rs	33	36	91.67%

Files with Coverage Reduction	New Missed Lines	%
src/ast/mod.rs	1	78.94%

Totals
Change from base Build 6914235970:	-0.007%
Covered Lines:	17845
Relevant Lines:	20346

---

💛 - Coveralls

[tobyhede]

The "simple" function syntax already works (eg CONVERT(DECIMAL(10, 5), 42))

You can possibly make the code simpler by keep this behaviour and adding the more complex CONVERT statement parsing if it is detected.

Adding something like the following in the parser.

if self.parse_keyword(Keyword::USING) {
   // build CONVERT exp
} else {
  // default to existing parse_function
}

This approach would remove the need for the check for function order and mean CONVERT struct would not need so many Optional types as you only ever use it for the "complex" CONVERT statements.

[lovasoa]

@tobyhede , we cannot do a if self.parse_keyword(Keyword::USING) { after having already parsed the first argument as a data type. In the MySQL syntax, the first argument is an expression, not a data type.

[lovasoa]

The "simple" function syntax already works (eg CONVERT(DECIMAL(10, 5), 42))

Does it ? I think CONVERT(DECIMAL(10, 5), 42) is parsed incorrectly today. DECIMAL(10, 5) would be parsed as an expression (a function call) instead of a data type.

[alamb]

Does it ? I think CONVERT(DECIMAL(10, 5), 42) is parsed incorrectly today. DECIMAL(10, 5) would be parsed as an expression (a function call) instead of a data type.

I agree this is what it seems to do:

$ echo "select CONVERT(DECIMAL(10, 5), 42)" > /tmp/foo.sql
$ cargo run --example cli -- /tmp/foo.sql
    Finished dev [unoptimized + debuginfo] target(s) in 0.07s
     Running `target/debug/examples/cli /tmp/foo.sql`
Parsing from file '/tmp/foo.sql' using GenericDialect
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] Parsing sql 'select CONVERT(DECIMAL(10, 5), 42)
'...
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] parsing expr
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] parsing expr
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] parsing expr
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] prefix: Value(Number("10", false))
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] get_next_precedence() TokenWithLocation { token: Comma, location: Location { line: 1, column: 26 } }
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] 0: , 1: 5 2: )
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] next precedence: 0
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] parsing expr
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] prefix: Value(Number("5", false))
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] get_next_precedence() TokenWithLocation { token: RParen, location: Location { line: 1, column: 29 } }
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] 0: ) 1: , 2: 42
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] next precedence: 0
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] prefix: Function(Function { name: ObjectName([Ident { value: "DECIMAL", quote_style: None }]), args: [Unnamed(Expr(Value(Number("10", false)))), Unnamed(Expr(Value(Number("5", false))))], filter: None, null_treatment: None, over: None, distinct: false, special: false, order_by: [] })
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] get_next_precedence() TokenWithLocation { token: Comma, location: Location { line: 1, column: 30 } }
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] 0: , 1: 42 2: )
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] next precedence: 0
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] parsing expr
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] prefix: Value(Number("42", false))
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] get_next_precedence() TokenWithLocation { token: RParen, location: Location { line: 1, column: 34 } }
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] 0: ) 1: EOF 2: EOF
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] next precedence: 0
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] prefix: Function(Function { name: ObjectName([Ident { value: "CONVERT", quote_style: None }]), args: [Unnamed(Expr(Function(Function { name: ObjectName([Ident { value: "DECIMAL", quote_style: None }]), args: [Unnamed(Expr(Value(Number("10", false)))), Unnamed(Expr(Value(Number("5", false))))], filter: None, null_treatment: None, over: None, distinct: false, special: false, order_by: [] }))), Unnamed(Expr(Value(Number("42", false))))], filter: None, null_treatment: None, over: None, distinct: false, special: false, order_by: [] })
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] get_next_precedence() TokenWithLocation { token: EOF, location: Location { line: 0, column: 0 } }
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] 0: EOF 1: EOF 2: EOF
2023-11-20T19:50:50.259Z DEBUG [sqlparser::parser] next precedence: 0
Round-trip:
'SELECT CONVERT(DECIMAL(10, 5), 42)'
Parse results:
[
    Query(
        Query {
            with: None,
            body: Select(
                Select {
                    distinct: None,
                    top: None,
                    projection: [
                        UnnamedExpr(
                            Function(
                                Function {
                                    name: ObjectName(
                                        [
                                            Ident {
                                                value: "CONVERT",
                                                quote_style: None,
                                            },
                                        ],
                                    ),
                                    args: [
                                        Unnamed(
                                            Expr(
                                                Function(
                                                    Function {
                                                        name: ObjectName(
                                                            [
                                                                Ident {
                                                                    value: "DECIMAL",
                                                                    quote_style: None,
                                                                },
                                                            ],
                                                        ),
                                                        args: [
                                                            Unnamed(
                                                                Expr(
                                                                    Value(
                                                                        Number(
                                                                            "10",
                                                                            false,
                                                                        ),
                                                                    ),
                                                                ),
                                                            ),
                                                            Unnamed(
                                                                Expr(
                                                                    Value(
                                                                        Number(
                                                                            "5",
                                                                            false,
                                                                        ),
                                                                    ),
                                                                ),
                                                            ),
                                                        ],
                                                        filter: None,
                                                        null_treatment: None,
                                                        over: None,
                                                        distinct: false,
                                                        special: false,
                                                        order_by: [],
                                                    },
                                                ),
                                            ),
                                        ),
                                        Unnamed(
                                            Expr(
                                                Value(
                                                    Number(
                                                        "42",
                                                        false,
                                                    ),
                                                ),
                                            ),
                                        ),
                                    ],
                                    filter: None,
                                    null_treatment: None,
                                    over: None,
                                    distinct: false,
                                    special: false,
                                    order_by: [],
                                },
                            ),
                        ),
                    ],
                    into: None,
                    from: [],
                    lateral_views: [],
                    selection: None,
                    group_by: Expressions(
                        [],
                    ),
                    cluster_by: [],
                    distribute_by: [],
                    sort_by: [],
                    having: None,
                    named_window: [],
                    qualify: None,
                },
            ),
            order_by: [],
            limit: None,
            limit_by: [],
            offset: None,
            fetch: None,
            locks: [],
            for_clause: None,
        },
    ),
]

[alamb]

Looks good to me. Thank you for the contribution @lovasoa

[alamb]

FWIW Postgres calls this "conversion name" but that appears to be an ObjectName so 👍

https://www.postgresql.org/docs/8.2/functions-string.html

[alamb]

🤯