don't auto quote leading underscore

sqlglot/expressions.py

@@ -1379,7 +1379,7 @@ def limit(self, expression, dialect=None, copy=True, **opts) -> Select:
 
         Example:
             >>> select("1").union(select("1")).limit(1).sql()
-            'SELECT * FROM (SELECT 1 UNION SELECT 1) AS "_l_0" LIMIT 1'
+            'SELECT * FROM (SELECT 1 UNION SELECT 1) AS _l_0 LIMIT 1'
 
         Args:
             expression (str | int | Expression): the SQL code string to parse.
@@ -3594,7 +3594,7 @@ def paren(expression) -> Paren:
     return Paren(this=expression)
 
 
-SAFE_IDENTIFIER_RE = re.compile(r"^[a-zA-Z][\w]*$")
+SAFE_IDENTIFIER_RE = re.compile(r"^[_a-zA-Z][\w]*$")
 
 
 def to_identifier(alias, quoted=None) -> t.Optional[Identifier]:

sqlglot/optimizer/unnest_subqueries.py

@@ -16,7 +16,7 @@ def unnest_subqueries(expression):
         >>> expression = sqlglot.parse_one("SELECT * FROM x AS x WHERE (SELECT y.a AS a FROM y AS y WHERE x.a = y.a) = 1 ")
         >>> unnest_subqueries(expression).sql()
         'SELECT * FROM x AS x LEFT JOIN (SELECT y.a AS a FROM y AS y WHERE TRUE GROUP BY y.a)\
- AS "_u_0" ON x.a = "_u_0".a WHERE ("_u_0".a = 1 AND NOT "_u_0".a IS NULL)'
+ AS _u_0 ON x.a = _u_0.a WHERE (_u_0.a = 1 AND NOT _u_0.a IS NULL)'
 
     Args:
         expression (sqlglot.Expression): expression to unnest

tests/dialects/test_redshift.py

@@ -53,7 +53,7 @@ def test_redshift(self):
         self.validate_all(
             "SELECT DISTINCT ON (a) a, b FROM x ORDER BY c DESC",
             write={
-                "redshift": 'SELECT a, b FROM (SELECT a, b, ROW_NUMBER() OVER (PARTITION BY a ORDER BY c DESC) AS "_row_number" FROM x) WHERE "_row_number" = 1',
+                "redshift": 'SELECT a, b FROM (SELECT a, b, ROW_NUMBER() OVER (PARTITION BY a ORDER BY c DESC) AS _row_number FROM x) WHERE "_row_number" = 1',
             },
         )
         self.validate_all(

tests/fixtures/optimizer/pushdown_projections.sql

@@ -1,32 +1,32 @@
 SELECT a FROM (SELECT * FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a FROM x AS x) AS _q_0;
 
 SELECT 1 FROM (SELECT * FROM x) WHERE b = 2;
-SELECT 1 AS "_col_0" FROM (SELECT x.b AS b FROM x AS x) AS "_q_0" WHERE "_q_0".b = 2;
+SELECT 1 AS _col_0 FROM (SELECT x.b AS b FROM x AS x) AS _q_0 WHERE _q_0.b = 2;
 
 SELECT (SELECT c FROM y WHERE q.b = y.b) FROM (SELECT * FROM x) AS q;
-SELECT (SELECT y.c AS c FROM y AS y WHERE q.b = y.b) AS "_col_0" FROM (SELECT x.b AS b FROM x AS x) AS q;
+SELECT (SELECT y.c AS c FROM y AS y WHERE q.b = y.b) AS _col_0 FROM (SELECT x.b AS b FROM x AS x) AS q;
 
 SELECT a FROM x JOIN (SELECT b, c FROM y) AS z ON x.b = z.b;
 SELECT x.a AS a FROM x AS x JOIN (SELECT y.b AS b FROM y AS y) AS z ON x.b = z.b;
 
 SELECT x1.a FROM (SELECT * FROM x) AS x1, (SELECT * FROM x) AS x2;
-SELECT x1.a AS a FROM (SELECT x.a AS a FROM x AS x) AS x1, (SELECT 1 AS "_" FROM x AS x) AS x2;
+SELECT x1.a AS a FROM (SELECT x.a AS a FROM x AS x) AS x1, (SELECT 1 AS _ FROM x AS x) AS x2;
 
 SELECT x1.a FROM (SELECT * FROM x) AS x1, (SELECT * FROM x) AS x2;
-SELECT x1.a AS a FROM (SELECT x.a AS a FROM x AS x) AS x1, (SELECT 1 AS "_" FROM x AS x) AS x2;
+SELECT x1.a AS a FROM (SELECT x.a AS a FROM x AS x) AS x1, (SELECT 1 AS _ FROM x AS x) AS x2;
 
 SELECT a FROM (SELECT DISTINCT a, b FROM x);
-SELECT "_q_0".a AS a FROM (SELECT DISTINCT x.a AS a, x.b AS b FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT DISTINCT x.a AS a, x.b AS b FROM x AS x) AS _q_0;
 
 SELECT a FROM (SELECT a, b FROM x UNION ALL SELECT a, b FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a FROM x AS x UNION ALL SELECT x.a AS a FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a FROM x AS x UNION ALL SELECT x.a AS a FROM x AS x) AS _q_0;
 
 WITH t1 AS (SELECT x.a AS a, x.b AS b FROM x UNION ALL SELECT z.b AS b, z.c AS c FROM z) SELECT a, b FROM t1;
 WITH t1 AS (SELECT x.a AS a, x.b AS b FROM x AS x UNION ALL SELECT z.b AS b, z.c AS c FROM z AS z) SELECT t1.a AS a, t1.b AS b FROM t1;
 
 SELECT a FROM (SELECT a, b FROM x UNION SELECT a, b FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a, x.b AS b FROM x AS x UNION SELECT x.a AS a, x.b AS b FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a, x.b AS b FROM x AS x UNION SELECT x.a AS a, x.b AS b FROM x AS x) AS _q_0;
 
 WITH y AS (SELECT * FROM x) SELECT a FROM y;
 WITH y AS (SELECT x.a AS a FROM x AS x) SELECT y.a AS a FROM y;
@@ -38,10 +38,10 @@ WITH z AS (SELECT * FROM x) SELECT a FROM z UNION SELECT a FROM z;
 WITH z AS (SELECT x.a AS a FROM x AS x) SELECT z.a AS a FROM z UNION SELECT z.a AS a FROM z;
 
 SELECT b FROM (SELECT a, SUM(b) AS b FROM x GROUP BY a);
-SELECT "_q_0".b AS b FROM (SELECT SUM(x.b) AS b FROM x AS x GROUP BY x.a) AS "_q_0";
+SELECT _q_0.b AS b FROM (SELECT SUM(x.b) AS b FROM x AS x GROUP BY x.a) AS _q_0;
 
 SELECT b FROM (SELECT a, SUM(b) AS b FROM x ORDER BY a);
-SELECT "_q_0".b AS b FROM (SELECT x.a AS a, SUM(x.b) AS b FROM x AS x ORDER BY a) AS "_q_0";
+SELECT _q_0.b AS b FROM (SELECT x.a AS a, SUM(x.b) AS b FROM x AS x ORDER BY a) AS _q_0;
 
 SELECT x FROM (VALUES(1, 2)) AS q(x, y);
 SELECT q.x AS x FROM (VALUES (1, 2)) AS q(x, y);

tests/fixtures/optimizer/qualify_columns.sql

@@ -21,15 +21,15 @@ SELECT x.a AS b FROM x AS x;
 
 # execute: false
 SELECT 1, 2 FROM x;
-SELECT 1 AS "_col_0", 2 AS "_col_1" FROM x AS x;
+SELECT 1 AS _col_0, 2 AS _col_1 FROM x AS x;
 
 # execute: false
 SELECT a + b FROM x;
-SELECT x.a + x.b AS "_col_0" FROM x AS x;
+SELECT x.a + x.b AS _col_0 FROM x AS x;
 
 # execute: false
 SELECT a, SUM(b) FROM x WHERE a > 1 AND b > 1 GROUP BY a;
-SELECT x.a AS a, SUM(x.b) AS "_col_1" FROM x AS x WHERE x.a > 1 AND x.b > 1 GROUP BY x.a;
+SELECT x.a AS a, SUM(x.b) AS _col_1 FROM x AS x WHERE x.a > 1 AND x.b > 1 GROUP BY x.a;
 
 SELECT SUM(a) AS c FROM x HAVING SUM(a) > 3;
 SELECT SUM(x.a) AS c FROM x AS x HAVING SUM(x.a) > 3;
@@ -59,7 +59,7 @@ SELECT SUM(x.a) AS c, SUM(x.b) AS d FROM x AS x ORDER BY SUM(x.a), SUM(x.b);
 
 # execute: false
 SELECT SUM(a), SUM(b) AS c FROM x ORDER BY 1, 2;
-SELECT SUM(x.a) AS "_col_0", SUM(x.b) AS c FROM x AS x ORDER BY SUM(x.a), SUM(x.b);
+SELECT SUM(x.a) AS _col_0, SUM(x.b) AS c FROM x AS x ORDER BY SUM(x.a), SUM(x.b);
 
 SELECT a AS j, b FROM x GROUP BY j, b;
 SELECT x.a AS j, x.b AS b FROM x AS x GROUP BY x.a, x.b;
@@ -72,7 +72,7 @@ SELECT x.a AS a, x.b AS b FROM x AS x ORDER BY x.a, x.b;
 
 # execute: false
 SELECT DATE(a), DATE(b) AS c FROM x GROUP BY 1, 2;
-SELECT DATE(x.a) AS "_col_0", DATE(x.b) AS c FROM x AS x GROUP BY DATE(x.a), DATE(x.b);
+SELECT DATE(x.a) AS _col_0, DATE(x.b) AS c FROM x AS x GROUP BY DATE(x.a), DATE(x.b);
 
 SELECT SUM(x.a) AS c FROM x JOIN y ON x.b = y.b GROUP BY c;
 SELECT SUM(x.a) AS c FROM x AS x JOIN y AS y ON x.b = y.b GROUP BY y.c;
@@ -130,10 +130,10 @@ SELECT a FROM (SELECT a FROM x AS x) y;
 SELECT y.a AS a FROM (SELECT x.a AS a FROM x AS x) AS y;
 
 SELECT a FROM (SELECT a AS a FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a FROM x AS x) AS _q_0;
 
 SELECT a FROM (SELECT a FROM (SELECT a FROM x));
-SELECT "_q_1".a AS a FROM (SELECT "_q_0".a AS a FROM (SELECT x.a AS a FROM x AS x) AS "_q_0") AS "_q_1";
+SELECT _q_1.a AS a FROM (SELECT _q_0.a AS a FROM (SELECT x.a AS a FROM x AS x) AS _q_0) AS _q_1;
 
 SELECT x.a FROM x AS x JOIN (SELECT * FROM x) AS y ON x.a = y.a;
 SELECT x.a AS a FROM x AS x JOIN (SELECT x.a AS a, x.b AS b FROM x AS x) AS y ON x.a = y.a;
@@ -157,7 +157,7 @@ SELECT a FROM x UNION SELECT a FROM x UNION SELECT a FROM x;
 SELECT x.a AS a FROM x AS x UNION SELECT x.a AS a FROM x AS x UNION SELECT x.a AS a FROM x AS x;
 
 SELECT a FROM (SELECT a FROM x UNION SELECT a FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a FROM x AS x UNION SELECT x.a AS a FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a FROM x AS x UNION SELECT x.a AS a FROM x AS x) AS _q_0;
 
 --------------------------------------
 -- Subqueries
@@ -167,10 +167,10 @@ SELECT x.a AS a FROM x AS x WHERE x.b IN (SELECT y.c AS c FROM y AS y);
 
 # execute: false
 SELECT (SELECT c FROM y) FROM x;
-SELECT (SELECT y.c AS c FROM y AS y) AS "_col_0" FROM x AS x;
+SELECT (SELECT y.c AS c FROM y AS y) AS _col_0 FROM x AS x;
 
 SELECT a FROM (SELECT a FROM x) WHERE a IN (SELECT b FROM (SELECT b FROM y));
-SELECT "_q_1".a AS a FROM (SELECT x.a AS a FROM x AS x) AS "_q_1" WHERE "_q_1".a IN (SELECT "_q_0".b AS b FROM (SELECT y.b AS b FROM y AS y) AS "_q_0");
+SELECT _q_1.a AS a FROM (SELECT x.a AS a FROM x AS x) AS _q_1 WHERE _q_1.a IN (SELECT _q_0.b AS b FROM (SELECT y.b AS b FROM y AS y) AS _q_0);
 
 --------------------------------------
 -- Correlated subqueries
@@ -215,10 +215,10 @@ SELECT x.*, y.* FROM x JOIN y ON x.b = y.b;
 SELECT x.a AS a, x.b AS b, y.b AS b, y.c AS c FROM x AS x JOIN y AS y ON x.b = y.b;
 
 SELECT a FROM (SELECT * FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a, x.b AS b FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a, x.b AS b FROM x AS x) AS _q_0;
 
 SELECT * FROM (SELECT a FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a FROM x AS x) AS _q_0;
 
 --------------------------------------
 -- CTEs

tests/fixtures/optimizer/qualify_columns__with_invisible.sql

@@ -11,10 +11,10 @@ SELECT x.b AS b FROM x AS x;
 -- Derived tables
 --------------------------------------
 SELECT x.a FROM x AS x JOIN (SELECT * FROM x);
-SELECT x.a AS a FROM x AS x JOIN (SELECT x.a AS a FROM x AS x) AS "_q_0";
+SELECT x.a AS a FROM x AS x JOIN (SELECT x.a AS a FROM x AS x) AS _q_0;
 
 SELECT x.b FROM x AS x JOIN (SELECT b FROM x);
-SELECT x.b AS b FROM x AS x JOIN (SELECT x.b AS b FROM x AS x) AS "_q_0";
+SELECT x.b AS b FROM x AS x JOIN (SELECT x.b AS b FROM x AS x) AS _q_0;
 
 --------------------------------------
 -- Expand *
@@ -29,7 +29,7 @@ SELECT * FROM y JOIN z ON y.c = z.c;
 SELECT y.b AS b, z.b AS b FROM y AS y JOIN z AS z ON y.c = z.c;
 
 SELECT a FROM (SELECT * FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a FROM x AS x) AS _q_0;
 
 SELECT * FROM (SELECT a FROM x);
-SELECT "_q_0".a AS a FROM (SELECT x.a AS a FROM x AS x) AS "_q_0";
+SELECT _q_0.a AS a FROM (SELECT x.a AS a FROM x AS x) AS _q_0;

tests/fixtures/optimizer/unnest_subqueries.sql

@@ -30,30 +30,30 @@ CROSS JOIN (
   SELECT
     SUM(y.a) AS a
   FROM y
-) AS "_u_0"
+) AS _u_0
 LEFT JOIN (
   SELECT
     y.a AS a
   FROM y
   GROUP BY
     y.a
-) AS "_u_1"
+) AS _u_1
   ON x.a = "_u_1"."a"
 LEFT JOIN (
   SELECT
     y.b AS b
   FROM y
   GROUP BY
     y.b
-) AS "_u_2"
+) AS _u_2
   ON x.a = "_u_2"."b"
 LEFT JOIN (
   SELECT
     y.a AS a
   FROM y
   GROUP BY
     y.a
-) AS "_u_3"
+) AS _u_3
   ON x.a = "_u_3"."a"
 LEFT JOIN (
   SELECT
@@ -64,8 +64,8 @@ LEFT JOIN (
     TRUE
   GROUP BY
     y.a
-) AS "_u_4"
-  ON x.a = "_u_4"."_u_5"
+) AS _u_4
+  ON x.a = _u_4._u_5
 LEFT JOIN (
   SELECT
     SUM(y.b) AS b,
@@ -75,8 +75,8 @@ LEFT JOIN (
     TRUE
   GROUP BY
     y.a
-) AS "_u_6"
-  ON x.a = "_u_6"."_u_7"
+) AS _u_6
+  ON x.a = _u_6._u_7
 LEFT JOIN (
   SELECT
     y.a AS a
@@ -85,8 +85,8 @@ LEFT JOIN (
     TRUE
   GROUP BY
     y.a
-) AS "_u_8"
-  ON "_u_8".a = x.a
+) AS _u_8
+  ON _u_8.a = x.a
 LEFT JOIN (
   SELECT
     y.a AS a
@@ -95,8 +95,8 @@ LEFT JOIN (
     TRUE
   GROUP BY
     y.a
-) AS "_u_9"
-  ON "_u_9".a = x.a
+) AS _u_9
+  ON _u_9.a = x.a
 LEFT JOIN (
   SELECT
     ARRAY_AGG(y.a) AS a,
@@ -106,8 +106,8 @@ LEFT JOIN (
     TRUE
   GROUP BY
     y.b
-) AS "_u_10"
-  ON "_u_10"."_u_11" = x.a
+) AS _u_10
+  ON _u_10._u_11 = x.a
 LEFT JOIN (
   SELECT
     SUM(y.a) AS a,
@@ -118,8 +118,8 @@ LEFT JOIN (
     TRUE AND TRUE AND TRUE
   GROUP BY
     y.a
-) AS "_u_12"
-  ON "_u_12"."_u_13" = x.a AND "_u_12"."_u_13" = x.b
+) AS _u_12
+  ON _u_12._u_13 = x.a AND _u_12._u_13 = x.b
 LEFT JOIN (
   SELECT
     y.a AS a
@@ -128,38 +128,38 @@ LEFT JOIN (
     TRUE
   GROUP BY
     y.a
-) AS "_u_15"
-  ON x.a = "_u_15".a
+) AS _u_15
+  ON x.a = _u_15.a
 WHERE
-  x.a = "_u_0".a
+  x.a = _u_0.a
   AND NOT "_u_1"."a" IS NULL
   AND NOT "_u_2"."b" IS NULL
   AND NOT "_u_3"."a" IS NULL
   AND (
-    x.a = "_u_4".b AND NOT "_u_4"."_u_5" IS NULL
+    x.a = _u_4.b AND NOT _u_4._u_5 IS NULL
   )
   AND (
-    x.a > "_u_6".b AND NOT "_u_6"."_u_7" IS NULL
+    x.a > _u_6.b AND NOT _u_6._u_7 IS NULL
   )
   AND (
-    None = "_u_8".a AND NOT "_u_8".a IS NULL
+    None = _u_8.a AND NOT _u_8.a IS NULL
   )
   AND NOT (
-    x.a = "_u_9".a AND NOT "_u_9".a IS NULL
+    x.a = _u_9.a AND NOT _u_9.a IS NULL
   )
   AND (
-    ARRAY_ANY("_u_10".a, _x -> _x = x.a) AND NOT "_u_10"."_u_11" IS NULL
+    ARRAY_ANY(_u_10.a, _x -> _x = x.a) AND NOT _u_10._u_11 IS NULL
   )
   AND (
     (
       (
-        x.a < "_u_12".a AND NOT "_u_12"."_u_13" IS NULL
-      ) AND NOT "_u_12"."_u_13" IS NULL
+        x.a < _u_12.a AND NOT _u_12._u_13 IS NULL
+      ) AND NOT _u_12._u_13 IS NULL
     )
-    AND ARRAY_ANY("_u_12"."_u_14", "_x" -> "_x" <> x.d)
+    AND ARRAY_ANY(_u_12._u_14, "_x" -> _x <> x.d)
   )
   AND (
-    NOT "_u_15".a IS NULL AND NOT "_u_15".a IS NULL
+    NOT _u_15.a IS NULL AND NOT _u_15.a IS NULL
   )
   AND x.a IN (
     SELECT
@@ -200,31 +200,3 @@ WHERE
       y.a = x.a
     OFFSET 10
   );
-
-SELECT
-  (
-    SELECT
-      s.name AS name
-    FROM student AS s
-    WHERE
-      s.sid = e.sid
-  ) AS sname
-FROM enrolled AS e
-WHERE
-  e.cid = '15-445';
-SELECT
-  "_u_0".name AS sname
-FROM enrolled AS e
-LEFT JOIN (
-  SELECT
-    MAX(s.name) AS name,
-    s.sid AS _u_1
-  FROM student AS s
-  WHERE
-    TRUE
-  GROUP BY
-    s.sid
-) AS "_u_0"
-  ON "_u_0"."_u_1" = e.sid
-WHERE
-  e.cid = '15-445';

tests/test_expressions.py

@@ -492,7 +492,7 @@ def test_alias(self):
         self.assertEqual(alias("foo", "bar-1").sql(), 'foo AS "bar-1"')
         self.assertEqual(alias("foo", "bar_1").sql(), "foo AS bar_1")
         self.assertEqual(alias("foo * 2", "2bar").sql(), 'foo * 2 AS "2bar"')
-        self.assertEqual(alias('"foo"', "_bar").sql(), '"foo" AS "_bar"')
+        self.assertEqual(alias('"foo"', "_bar").sql(), '"foo" AS _bar')
         self.assertEqual(alias("foo", "bar", quoted=True).sql(), 'foo AS "bar"')
 
     def test_unit(self):
@@ -504,6 +504,8 @@ def test_unit(self):
     def test_identifier(self):
         self.assertTrue(exp.to_identifier('"x"').quoted)
         self.assertFalse(exp.to_identifier("x").quoted)
+        self.assertTrue(exp.to_identifier("foo ").quoted)
+        self.assertFalse(exp.to_identifier("_x").quoted)
 
     def test_function_normalizer(self):
         self.assertEqual(parse_one("HELLO()").sql(normalize_functions="lower"), "hello()")