Fix: correctly handle follow-tokens for unit-less intervals (#7529)

Author: jvstein

sqlglot/parser.py

@@ -5829,17 +5829,15 @@ def _parse_interval_span(self, this: exp.Expr) -> exp.Interval:
 
             self._retreat(index)
 
-        unit = (
-            None
-            if interval_span_units_omitted
-            else (
-                self._parse_function()
-                or (
-                    not self._match_set((TokenType.ALIAS, TokenType.DCOLON), advance=False)
-                    and self._parse_var(any_token=True, upper=True)
-                )
-            )
-        )
+        if interval_span_units_omitted:
+            unit = None
+        else:
+            unit = self._parse_function()
+            if not unit and (
+                self._curr.token_type == TokenType.VAR
+                or self._curr.text.upper() in self.dialect.VALID_INTERVAL_UNITS
+            ):
+                unit = self._parse_var(any_token=True, upper=True)
 
         # Most dialects support, e.g., the form INTERVAL '5' day, thus we try to parse
         # each INTERVAL expression into this canonical form so it's easy to transpile

tests/dialects/test_postgres.py

@@ -91,6 +91,16 @@ def test_postgres(self):
         self.validate_identity("SELECT INTERVAL '2.5 MONTH'")
         self.validate_identity("SELECT INTERVAL '-10.75 MINUTE'")
         self.validate_identity("SELECT INTERVAL '0.123456789 SECOND'")
+        self.validate_identity("SELECT date_col - INTERVAL '30' FROM t")
+        self.validate_identity("SELECT date_col - INTERVAL '1' AS one_second_later")
+        self.validate_identity(
+            "SELECT date_col - INTERVAL '30' DAY FROM t",
+            "SELECT date_col - INTERVAL '30 DAY' FROM t",
+        )
+        self.validate_identity(
+            "SELECT date_col - INTERVAL '1' HOUR AS one_hour_later",
+            "SELECT date_col - INTERVAL '1 HOUR' AS one_hour_later",
+        )
         self.validate_identity(
             "SELECT SUM(x) OVER (PARTITION BY y ORDER BY interval ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) - SUM(x) OVER (PARTITION BY y ORDER BY interval ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS total"
         )

tests/dialects/test_redshift.py

@@ -344,6 +344,16 @@ def test_identity(self):
         self.validate_identity("SELECT DATEADD(DAY, 1, 'today')")
         self.validate_identity("SELECT * FROM #x")
         self.validate_identity("SELECT INTERVAL '5 DAY'")
+        self.validate_identity("SELECT date_col - INTERVAL '30' FROM t")
+        self.validate_identity("SELECT date_col - INTERVAL '1' AS one_second_later")
+        self.validate_identity(
+            "SELECT date_col - INTERVAL '30' DAY FROM t",
+            "SELECT date_col - INTERVAL '30 DAY' FROM t",
+        )
+        self.validate_identity(
+            "SELECT date_col - INTERVAL '1' HOUR AS one_hour_later",
+            "SELECT date_col - INTERVAL '1 HOUR' AS one_hour_later",
+        )
         self.validate_identity("foo$")
         self.validate_identity("CAST('bla' AS SUPER)")
         self.validate_identity("CREATE TABLE real1 (realcol REAL)")