Support UNNEST as a table factor for PostgreSQL (#968)

src/parser/mod.rs

@@ -6240,7 +6240,7 @@ impl<'a> Parser<'a> {
                 // appearing alone in parentheses (e.g. `FROM (mytable)`)
                 self.expected("joined table", self.peek_token())
             }
-        } else if dialect_of!(self is BigQueryDialect | GenericDialect)
+        } else if dialect_of!(self is BigQueryDialect | PostgreSqlDialect | GenericDialect)
             && self.parse_keyword(Keyword::UNNEST)
         {
             self.expect_token(&Token::LParen)?;

tests/sqlparser_postgres.rs

@@ -3450,3 +3450,30 @@ fn parse_create_table_with_alias() {
         _ => unreachable!(),
     }
 }
+
+#[test]
+fn parse_join_constraint_unnest_alias() {
+    assert_eq!(
+        only(
+            pg().verified_only_select("SELECT * FROM t1 JOIN UNNEST(t1.a) AS f ON c1 = c2")
+                .from
+        )
+        .joins,
+        vec![Join {
+            relation: TableFactor::UNNEST {
+                alias: table_alias("f"),
+                array_exprs: vec![Expr::CompoundIdentifier(vec![
+                    Ident::new("t1"),
+                    Ident::new("a")
+                ])],
+                with_offset: false,
+                with_offset_alias: None
+            },
+            join_operator: JoinOperator::Inner(JoinConstraint::On(Expr::BinaryOp {
+                left: Box::new(Expr::Identifier("c1".into())),
+                op: BinaryOperator::Eq,
+                right: Box::new(Expr::Identifier("c2".into())),
+            })),
+        }]
+    );
+}