Support TABLE functions in FROM (#253)

Support `TABLE(...)` syntax in `FROM`, for example:

    select * from TABLE(SOME_FUNCTION(some_arg))

The ANSI spec allows routine invocations (and some other kinds of expressions we don't currently support) inside TABLE:
https://jakewheat.github.io/sql-overview/sql-2016-foundation-grammar.html#PTF-derived-table
https://jakewheat.github.io/sql-overview/sql-2016-foundation-grammar.html#table-function-derived-table

src/ast/query.rs

@@ -235,6 +235,11 @@ pub enum TableFactor {
         subquery: Box<Query>,
         alias: Option<TableAlias>,
     },
+    /// `TABLE(<expr>)[ AS <alias> ]`
+    TableFunction {
+        expr: Expr,
+        alias: Option<TableAlias>,
+    },
     /// Represents a parenthesized table factor. The SQL spec only allows a
     /// join expression (`(foo <JOIN> bar [ <JOIN> baz ... ])`) to be nested,
     /// possibly several times, but the parser also accepts the non-standard
@@ -278,6 +283,13 @@ impl fmt::Display for TableFactor {
                 }
                 Ok(())
             }
+            TableFactor::TableFunction { expr, alias } => {
+                write!(f, "TABLE({})", expr)?;
+                if let Some(alias) = alias {
+                    write!(f, " AS {}", alias)?;
+                }
+                Ok(())
+            }
             TableFactor::NestedJoin(table_reference) => write!(f, "({})", table_reference),
         }
     }

src/parser.rs

@@ -2066,10 +2066,15 @@ impl Parser {
             if !self.consume_token(&Token::LParen) {
                 self.expected("subquery after LATERAL", self.peek_token())?;
             }
-            return self.parse_derived_table_factor(Lateral);
-        }
-
-        if self.consume_token(&Token::LParen) {
+            self.parse_derived_table_factor(Lateral)
+        } else if self.parse_keyword(Keyword::TABLE) {
+            // parse table function (SELECT * FROM TABLE (<expr>) [ AS <alias> ])
+            self.expect_token(&Token::LParen)?;
+            let expr = self.parse_expr()?;
+            self.expect_token(&Token::RParen)?;
+            let alias = self.parse_optional_table_alias(keywords::RESERVED_FOR_TABLE_ALIAS)?;
+            Ok(TableFactor::TableFunction { expr, alias })
+        } else if self.consume_token(&Token::LParen) {
             // A left paren introduces either a derived table (i.e., a subquery)
             // or a nested join. It's nearly impossible to determine ahead of
             // time which it is... so we just try to parse both.

tests/sqlparser_common.rs

@@ -1158,8 +1158,8 @@ fn parse_create_table_with_multiple_on_delete_fails() {
 
 #[test]
 fn parse_assert() {
-    let sql = "ASSERT (SELECT COUNT(*) FROM table) > 0";
-    let ast = one_statement_parses_to(sql, "ASSERT (SELECT COUNT(*) FROM table) > 0");
+    let sql = "ASSERT (SELECT COUNT(*) FROM my_table) > 0";
+    let ast = one_statement_parses_to(sql, "ASSERT (SELECT COUNT(*) FROM my_table) > 0");
     match ast {
         Statement::Assert {
             condition: _condition,
@@ -1173,10 +1173,10 @@ fn parse_assert() {
 
 #[test]
 fn parse_assert_message() {
-    let sql = "ASSERT (SELECT COUNT(*) FROM table) > 0 AS 'No rows in table'";
+    let sql = "ASSERT (SELECT COUNT(*) FROM my_table) > 0 AS 'No rows in my_table'";
     let ast = one_statement_parses_to(
         sql,
-        "ASSERT (SELECT COUNT(*) FROM table) > 0 AS 'No rows in table'",
+        "ASSERT (SELECT COUNT(*) FROM my_table) > 0 AS 'No rows in my_table'",
     );
     match ast {
         Statement::Assert {
@@ -1184,7 +1184,7 @@ fn parse_assert_message() {
             message: Some(message),
         } => {
             match message {
-                Expr::Value(Value::SingleQuotedString(s)) => assert_eq!(s, "No rows in table"),
+                Expr::Value(Value::SingleQuotedString(s)) => assert_eq!(s, "No rows in my_table"),
                 _ => unreachable!(),
             };
         }
@@ -1864,6 +1864,39 @@ fn parse_simple_math_expr_minus() {
     verified_only_select(sql);
 }
 
+#[test]
+fn parse_table_function() {
+    let select = verified_only_select("SELECT * FROM TABLE(FUN('1')) AS a");
+
+    match only(select.from).relation {
+        TableFactor::TableFunction { expr, alias } => {
+            let expected_expr = Expr::Function(Function {
+                name: ObjectName(vec![Ident::new("FUN")]),
+                args: vec![FunctionArg::Unnamed(Expr::Value(
+                    Value::SingleQuotedString("1".to_owned()),
+                ))],
+                over: None,
+                distinct: false,
+            });
+            assert_eq!(expr, expected_expr);
+            assert_eq!(alias, table_alias("a"))
+        }
+        _ => panic!("Expecting TableFactor::TableFunction"),
+    }
+
+    let res = parse_sql_statements("SELECT * FROM TABLE '1' AS a");
+    assert_eq!(
+        ParserError::ParserError("Expected (, found: \'1\'".to_string()),
+        res.unwrap_err()
+    );
+
+    let res = parse_sql_statements("SELECT * FROM TABLE (FUN(a) AS a");
+    assert_eq!(
+        ParserError::ParserError("Expected ), found: AS".to_string()),
+        res.unwrap_err()
+    );
+}
+
 #[test]
 fn parse_delimited_identifiers() {
     // check that quoted identifiers in any position remain quoted after serialization