Snowflake: support for object constants (#1223)

Author: jmhain

src/dialect/duckdb.rs

@@ -37,4 +37,11 @@ impl Dialect for DuckDbDialect {
     fn supports_named_fn_args_with_eq_operator(&self) -> bool {
         true
     }
+
+    // DuckDB uses this syntax for `STRUCT`s.
+    //
+    // https://duckdb.org/docs/sql/data_types/struct.html#creating-structs
+    fn supports_dictionary_syntax(&self) -> bool {
+        true
+    }
 }

src/dialect/generic.rs

@@ -46,4 +46,8 @@ impl Dialect for GenericDialect {
     fn supports_start_transaction_modifier(&self) -> bool {
         true
     }
+
+    fn supports_dictionary_syntax(&self) -> bool {
+        true
+    }
 }

src/dialect/mod.rs

@@ -170,6 +170,11 @@ pub trait Dialect: Debug + Any {
     fn supports_named_fn_args_with_eq_operator(&self) -> bool {
         false
     }
+    /// Returns true if the dialect supports defining structs or objects using a
+    /// syntax like `{'x': 1, 'y': 2, 'z': 3}`.
+    fn supports_dictionary_syntax(&self) -> bool {
+        false
+    }
     /// Returns true if the dialect has a CONVERT function which accepts a type first
     /// and an expression second, e.g. `CONVERT(varchar, 1)`
     fn convert_type_before_value(&self) -> bool {

src/dialect/snowflake.rs

@@ -59,6 +59,14 @@ impl Dialect for SnowflakeDialect {
         true
     }
 
+    // Snowflake uses this syntax for "object constants" (the values of which
+    // are not actually required to be constants).
+    //
+    // https://docs.snowflake.com/en/sql-reference/data-types-semistructured#label-object-constant
+    fn supports_dictionary_syntax(&self) -> bool {
+        true
+    }
+
     fn parse_statement(&self, parser: &mut Parser) -> Option<Result<Statement, ParserError>> {
         if parser.parse_keyword(Keyword::CREATE) {
             // possibly CREATE STAGE

src/parser/mod.rs

@@ -1192,7 +1192,7 @@ impl<'a> Parser<'a> {
                 self.prev_token();
                 Ok(Expr::Value(self.parse_value()?))
             }
-            Token::LBrace if dialect_of!(self is DuckDbDialect | GenericDialect) => {
+            Token::LBrace if self.dialect.supports_dictionary_syntax() => {
                 self.prev_token();
                 self.parse_duckdb_struct_literal()
             }

tests/sqlparser_common.rs

@@ -9408,3 +9408,59 @@ fn insert_into_with_parentheses() {
     };
     dialects.verified_stmt("INSERT INTO t1 (id, name) (SELECT t2.id, t2.name FROM t2)");
 }
+
+#[test]
+fn test_dictionary_syntax() {
+    fn check(sql: &str, expect: Expr) {
+        assert_eq!(
+            all_dialects_where(|d| d.supports_dictionary_syntax()).verified_expr(sql),
+            expect
+        );
+    }
+
+    check(
+        "{'Alberta': 'Edmonton', 'Manitoba': 'Winnipeg'}",
+        Expr::Dictionary(vec![
+            DictionaryField {
+                key: Ident::with_quote('\'', "Alberta"),
+                value: Box::new(Expr::Value(Value::SingleQuotedString(
+                    "Edmonton".to_owned(),
+                ))),
+            },
+            DictionaryField {
+                key: Ident::with_quote('\'', "Manitoba"),
+                value: Box::new(Expr::Value(Value::SingleQuotedString(
+                    "Winnipeg".to_owned(),
+                ))),
+            },
+        ]),
+    );
+
+    check(
+        "{'start': CAST('2023-04-01' AS TIMESTAMP), 'end': CAST('2023-04-05' AS TIMESTAMP)}",
+        Expr::Dictionary(vec![
+            DictionaryField {
+                key: Ident::with_quote('\'', "start"),
+                value: Box::new(Expr::Cast {
+                    kind: CastKind::Cast,
+                    expr: Box::new(Expr::Value(Value::SingleQuotedString(
+                        "2023-04-01".to_owned(),
+                    ))),
+                    data_type: DataType::Timestamp(None, TimezoneInfo::None),
+                    format: None,
+                }),
+            },
+            DictionaryField {
+                key: Ident::with_quote('\'', "end"),
+                value: Box::new(Expr::Cast {
+                    kind: CastKind::Cast,
+                    expr: Box::new(Expr::Value(Value::SingleQuotedString(
+                        "2023-04-05".to_owned(),
+                    ))),
+                    data_type: DataType::Timestamp(None, TimezoneInfo::None),
+                    format: None,
+                }),
+            },
+        ]),
+    )
+}