Feat(oracle): support KEEP (.. [FIRST|LAST] ..) window function syntax

sqlglot/dialects/oracle.py

@@ -61,6 +61,8 @@ class Oracle(Dialect):
     }
 
     class Parser(parser.Parser):
+        WINDOW_BEFORE_PAREN_TOKENS = {TokenType.OVER, TokenType.KEEP}
+
         FUNCTIONS = {
             **parser.Parser.FUNCTIONS,  # type: ignore
             "SQUARE": lambda args: exp.Pow(this=seq_get(args, 0), expression=exp.Literal.number(2)),
@@ -166,6 +168,7 @@ class Tokenizer(tokens.Tokenizer):
             **tokens.Tokenizer.KEYWORDS,
             "(+)": TokenType.JOIN_MARKER,
             "COLUMNS": TokenType.COLUMN,
+            "KEEP": TokenType.KEEP,
             "MATCH_RECOGNIZE": TokenType.MATCH_RECOGNIZE,
             "MINUS": TokenType.EXCEPT,
             "NVARCHAR2": TokenType.NVARCHAR,

sqlglot/expressions.py

@@ -2772,6 +2772,8 @@ class Window(Expression):
         "order": False,
         "spec": False,
         "alias": False,
+        "over": False,
+        "first": False,
     }
 
 

sqlglot/generator.py

@@ -1553,12 +1553,18 @@ def window_sql(self, expression: exp.Window) -> str:
         spec_sql = " " + self.window_spec_sql(spec) if spec else ""
 
         alias = self.sql(expression, "alias")
-        this = f"{this} {'AS' if expression.arg_key == 'windows' else 'OVER'}"
+        over = self.sql(expression, "over") or "OVER"
+        this = f"{this} {'AS' if expression.arg_key == 'windows' else over}"
+
+        first = expression.args.get("first")
+        if first is not None:
+            first = " FIRST " if first else " LAST "
+        first = first or ""
 
         if not partition and not order and not spec and alias:
             return f"{this} {alias}"
 
-        window_args = alias + partition_sql + order_sql + spec_sql
+        window_args = alias + first + partition_sql + order_sql + spec_sql
 
         return f"{this} ({window_args.strip()})"
 

sqlglot/parser.py

@@ -750,6 +750,7 @@ class Parser(metaclass=_Parser):
     INSERT_ALTERNATIVES = {"ABORT", "FAIL", "IGNORE", "REPLACE", "ROLLBACK"}
 
     WINDOW_ALIAS_TOKENS = ID_VAR_TOKENS - {TokenType.ROWS}
+    WINDOW_BEFORE_PAREN_TOKENS = {TokenType.OVER}
 
     ADD_CONSTRAINT_TOKENS = {TokenType.CONSTRAINT, TokenType.PRIMARY_KEY, TokenType.FOREIGN_KEY}
 
@@ -3768,14 +3769,24 @@ def _parse_window(
 
         # bigquery select from window x AS (partition by ...)
         if alias:
+            over = None
             self._match(TokenType.ALIAS)
-        elif not self._match(TokenType.OVER):
+        elif not self._match_set(self.WINDOW_BEFORE_PAREN_TOKENS):
             return this
+        else:
+            over = self._prev.text.upper()
 
         if not self._match(TokenType.L_PAREN):
-            return self.expression(exp.Window, this=this, alias=self._parse_id_var(False))
+            return self.expression(
+                exp.Window, this=this, alias=self._parse_id_var(False), over=over
+            )
 
         window_alias = self._parse_id_var(any_token=False, tokens=self.WINDOW_ALIAS_TOKENS)
+
+        first = self._match(TokenType.FIRST)
+        if self._match_text_seq("LAST"):
+            first = False
+
         partition = self._parse_partition_by()
         order = self._parse_order()
         kind = self._match_set((TokenType.ROWS, TokenType.RANGE)) and self._prev.text
@@ -3806,6 +3817,8 @@ def _parse_window(
             order=order,
             spec=spec,
             alias=window_alias,
+            over=over,
+            first=first,
         )
 
     def _parse_window_spec(self) -> t.Dict[str, t.Optional[str | exp.Expression]]:

sqlglot/tokens.py

@@ -215,6 +215,7 @@ class TokenType(AutoName):
     ISNULL = auto()
     JOIN = auto()
     JOIN_MARKER = auto()
+    KEEP = auto()
     LANGUAGE = auto()
     LATERAL = auto()
     LAZY = auto()

tests/dialects/test_oracle.py

@@ -6,6 +6,9 @@ class TestOracle(Validator):
 
     def test_oracle(self):
         self.validate_identity("SELECT * FROM V$SESSION")
+        self.validate_identity(
+            "SELECT MIN(column_name) KEEP (DENSE_RANK FIRST ORDER BY column_name DESC) FROM table_name"
+        )
 
         self.validate_all(
             "NVL(NULL, 1)",

tests/test_transpile.py

@@ -20,6 +20,7 @@ def validate(self, sql, target, **kwargs):
         self.assertEqual(transpile(sql, **kwargs)[0], target)
 
     def test_alias(self):
+        self.assertEqual(transpile("SELECT SUM(y) KEEP")[0], "SELECT SUM(y) AS KEEP")
         self.assertEqual(transpile("SELECT 1 overwrite")[0], "SELECT 1 AS overwrite")
         self.assertEqual(transpile("SELECT 1 is")[0], "SELECT 1 AS is")
         self.assertEqual(transpile("SELECT 1 current_time")[0], "SELECT 1 AS current_time")