Support DISTINCT AS { STRUCT | VALUE } for BigQuery

src/ast/query.rs

@@ -3340,20 +3340,29 @@ impl fmt::Display for OpenJsonTableColumn {
 /// BigQuery supports ValueTables which have 2 modes:
 /// `SELECT AS STRUCT`
 /// `SELECT AS VALUE`
+///
+/// They can be combined with `[ { ALL | DISTINCT } ]`, e.g.
+/// `SELECT DISTINCT AS STRUCT`
+///
 /// <https://cloud.google.com/bigquery/docs/reference/standard-sql/query-syntax#value_tables>
+/// <https://cloud.google.com/bigquery/docs/reference/standard-sql/query-syntax#select_list>
 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
 pub enum ValueTableMode {
     AsStruct,
     AsValue,
+    DistinctAsStruct,
+    DistinctAsValue,
 }
 
 impl fmt::Display for ValueTableMode {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
             ValueTableMode::AsStruct => write!(f, "AS STRUCT"),
             ValueTableMode::AsValue => write!(f, "AS VALUE"),
+            ValueTableMode::DistinctAsStruct => write!(f, "DISTINCT AS STRUCT"),
+            ValueTableMode::DistinctAsValue => write!(f, "DISTINCT AS VALUE"),
         }
     }
 }

src/parser/mod.rs

@@ -11505,8 +11505,16 @@ impl<'a> Parser<'a> {
         }
 
         let select_token = self.expect_keyword(Keyword::SELECT)?;
-        let value_table_mode =
-            if dialect_of!(self is BigQueryDialect) && self.parse_keyword(Keyword::AS) {
+        let value_table_mode = if dialect_of!(self is BigQueryDialect) {
+            if self.parse_keywords(&[Keyword::DISTINCT, Keyword::AS]) {
+                if self.parse_keyword(Keyword::VALUE) {
+                    Some(ValueTableMode::DistinctAsValue)
+                } else if self.parse_keyword(Keyword::STRUCT) {
+                    Some(ValueTableMode::DistinctAsStruct)
+                } else {
+                    self.expected("VALUE or STRUCT", self.peek_token())?
+                }
+            } else if self.parse_keyword(Keyword::AS) {
                 if self.parse_keyword(Keyword::VALUE) {
                     Some(ValueTableMode::AsValue)
                 } else if self.parse_keyword(Keyword::STRUCT) {
@@ -11516,7 +11524,10 @@ impl<'a> Parser<'a> {
                 }
             } else {
                 None
-            };
+            }
+        } else {
+            None
+        };
 
         let mut top_before_distinct = false;
         let mut top = None;

tests/sqlparser_bigquery.rs

@@ -2377,3 +2377,14 @@ fn test_any_type() {
 fn test_any_type_dont_break_custom_type() {
     bigquery_and_generic().verified_stmt("CREATE TABLE foo (x ANY)");
 }
+
+#[test]
+fn test_select_distinct_as_struct_or_value() {
+    for sql in [
+        "SELECT DISTINCT AS STRUCT a, ABS(b) FROM UNNEST(c) AS T",
+        "SELECT DISTINCT AS VALUE a, ABS(b) FROM UNNEST(c) AS T",
+        "SELECT ARRAY(SELECT DISTINCT AS STRUCT a, b, ABS(c) AS c, ABS(d) AS d FROM UNNEST(e) AS T)",
+    ] {
+        bigquery().verified_stmt(sql);
+    }
+}