From be0de6ecdce6c5e4772e138dec9f9e452822c92b Mon Sep 17 00:00:00 2001
From: tobymao <toby.mao@gmail.com>
Date: Tue, 6 Jun 2023 22:07:37 -0700
Subject: [PATCH] Fix: window sql gen closes #1739

---
 sqlglot/generator.py        | 24 +++++++++---------------
 tests/fixtures/identity.sql |  1 +
 2 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/sqlglot/generator.py b/sqlglot/generator.py
index 4a6e472e9f..1aa96012f6 100644
--- a/sqlglot/generator.py
+++ b/sqlglot/generator.py
@@ -1651,32 +1651,26 @@ def where_sql(self, expression: exp.Where) -> str:
 
     def window_sql(self, expression: exp.Window) -> str:
         this = self.sql(expression, "this")
-
         partition = self.partition_by_sql(expression)
-
         order = expression.args.get("order")
-        order_sql = self.order_sql(order, flat=True) if order else ""
-
-        partition_sql = partition + " " if partition and order else partition
-
-        spec = expression.args.get("spec")
-        spec_sql = " " + self.windowspec_sql(spec) if spec else ""
-
+        order = self.order_sql(order, flat=True) if order else ""
+        spec = self.sql(expression, "spec")
         alias = self.sql(expression, "alias")
         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 first is None:
+            first = ""
+        else:
+            first = "FIRST" if first else "LAST"
 
         if not partition and not order and not spec and alias:
             return f"{this} {alias}"
 
-        window_args = alias + first + partition_sql + order_sql + spec_sql
-
-        return f"{this} ({window_args.strip()})"
+        args = " ".join(arg for arg in (alias, first, partition, order, spec) if arg)
+        return f"{this} ({args})"
 
     def partition_by_sql(self, expression: exp.Window | exp.MatchRecognize) -> str:
         partition = self.expressions(expression, key="partition_by", flat=True)
diff --git a/tests/fixtures/identity.sql b/tests/fixtures/identity.sql
index 0a1e305d4d..e4f83aba90 100644
--- a/tests/fixtures/identity.sql
+++ b/tests/fixtures/identity.sql
@@ -160,6 +160,7 @@ CASE WHEN SUM(x) > 3 THEN 1 END OVER (PARTITION BY x)
 SUM(ROW() OVER (PARTITION BY x))
 SUM(ROW() OVER (PARTITION BY x + 1))
 SUM(ROW() OVER (PARTITION BY x AND y))
+SUM(x) OVER (w ORDER BY y)
 (ROW() OVER ())
 CASE WHEN (x > 1) THEN 1 ELSE 0 END
 CASE (1) WHEN 1 THEN 1 ELSE 0 END