fix(postgres): Decouple UNIQUE from DEFAULT constraints (#3775)

Author: VaggelisD

sqlglot/dialects/postgres.py

@@ -447,6 +447,9 @@ def _parse_date_part(self) -> exp.Expression:
 
             return self.expression(exp.Extract, this=part, expression=value)
 
+        def _parse_unique_key(self) -> t.Optional[exp.Expression]:
+            return None
+
     class Generator(generator.Generator):
         SINGLE_STRING_INTERVAL = True
         RENAME_TABLE_WITH_DB = False

sqlglot/expressions.py

@@ -1869,7 +1869,7 @@ class TitleColumnConstraint(ColumnConstraintKind):
 
 
 class UniqueColumnConstraint(ColumnConstraintKind):
-    arg_types = {"this": False, "index_type": False, "on_conflict": False}
+    arg_types = {"this": False, "index_type": False, "on_conflict": False, "nulls": False}
 
 
 class UppercaseColumnConstraint(ColumnConstraintKind):

sqlglot/generator.py

@@ -961,7 +961,8 @@ def uniquecolumnconstraint_sql(self, expression: exp.UniqueColumnConstraint) ->
         index_type = f" USING {index_type}" if index_type else ""
         on_conflict = self.sql(expression, "on_conflict")
         on_conflict = f" {on_conflict}" if on_conflict else ""
-        return f"UNIQUE{this}{index_type}{on_conflict}"
+        nulls_sql = " NULLS NOT DISTINCT" if expression.args.get("nulls") else ""
+        return f"UNIQUE{nulls_sql}{this}{index_type}{on_conflict}"
 
     def createable_sql(self, expression: exp.Create, locations: t.DefaultDict) -> str:
         return self.sql(expression, "this")

sqlglot/parser.py

@@ -5179,11 +5179,15 @@ def _parse_unnamed_constraint(
 
         return self.CONSTRAINT_PARSERS[constraint](self)
 
+    def _parse_unique_key(self) -> t.Optional[exp.Expression]:
+        return self._parse_id_var(any_token=False)
+
     def _parse_unique(self) -> exp.UniqueColumnConstraint:
         self._match_text_seq("KEY")
         return self.expression(
             exp.UniqueColumnConstraint,
-            this=self._parse_schema(self._parse_id_var(any_token=False)),
+            nulls=self._match_text_seq("NULLS", "NOT", "DISTINCT"),
+            this=self._parse_schema(self._parse_unique_key()),
             index_type=self._match(TokenType.USING) and self._advance_any() and self._prev.text,
             on_conflict=self._parse_on_conflict(),
         )

tests/dialects/test_postgres.py

@@ -977,6 +977,10 @@ def test_ddl(self):
             },
         )
 
+        self.validate_identity("CREATE TABLE tbl (col INT UNIQUE NULLS NOT DISTINCT DEFAULT 9.99)")
+        self.validate_identity("CREATE TABLE tbl (col UUID UNIQUE DEFAULT GEN_RANDOM_UUID())")
+        self.validate_identity("CREATE TABLE tbl (col UUID, UNIQUE NULLS NOT DISTINCT (col))")
+
         with self.assertRaises(ParseError):
             transpile("CREATE TABLE products (price DECIMAL CHECK price > 0)", read="postgres")
         with self.assertRaises(ParseError):