Parse ARRAY_AGG for Bigquery and Snowflake (#662)

src/parser.rs

@@ -473,6 +473,7 @@ impl<'a> Parser<'a> {
                     self.expect_token(&Token::LParen)?;
                     self.parse_array_subquery()
                 }
+                Keyword::ARRAY_AGG => self.parse_array_agg_expr(),
                 Keyword::NOT => self.parse_not(),
                 // Here `w` is a word, check if it's a part of a multi-part
                 // identifier, a function call, or a simple identifier:
@@ -1071,6 +1072,54 @@ impl<'a> Parser<'a> {
         }))
     }
 
+    pub fn parse_array_agg_expr(&mut self) -> Result<Expr, ParserError> {
+        self.expect_token(&Token::LParen)?;
+        let distinct = self.parse_keyword(Keyword::DISTINCT);
+        let expr = Box::new(self.parse_expr()?);
+        // ANSI SQL and BigQuery define ORDER BY inside function.
+        if !self.dialect.supports_within_after_array_aggregation() {
+            let order_by = if self.parse_keywords(&[Keyword::ORDER, Keyword::BY]) {
+                let order_by_expr = self.parse_order_by_expr()?;
+                Some(Box::new(order_by_expr))
+            } else {
+                None
+            };
+            let limit = if self.parse_keyword(Keyword::LIMIT) {
+                self.parse_limit()?.map(Box::new)
+            } else {
+                None
+            };
+            self.expect_token(&Token::RParen)?;
+            return Ok(Expr::ArrayAgg(ArrayAgg {
+                distinct,
+                expr,
+                order_by,
+                limit,
+                within_group: false,
+            }));
+        }
+        // Snowflake defines ORDERY BY in within group instead of inside the function like
+        // ANSI SQL.
+        self.expect_token(&Token::RParen)?;
+        let within_group = if self.parse_keywords(&[Keyword::WITHIN, Keyword::GROUP]) {
+            self.expect_token(&Token::LParen)?;
+            self.expect_keywords(&[Keyword::ORDER, Keyword::BY])?;
+            let order_by_expr = self.parse_order_by_expr()?;
+            self.expect_token(&Token::RParen)?;
+            Some(Box::new(order_by_expr))
+        } else {
+            None
+        };
+
+        Ok(Expr::ArrayAgg(ArrayAgg {
+            distinct,
+            expr,
+            order_by: within_group,
+            limit: None,
+            within_group: true,
+        }))
+    }
+
     // This function parses date/time fields for the EXTRACT function-like
     // operator, interval qualifiers, and the ceil/floor operations.
     // EXTRACT supports a wider set of date/time fields than interval qualifiers,