From 885990f2f7bfea00a3c1770b8b718ae7756da652 Mon Sep 17 00:00:00 2001
From: c3us-dev <ccorbridge@ceeus.com>
Date: Wed, 28 Jan 2026 19:28:26 -0500
Subject: [PATCH] add narrow lateral_sql for postgres dialect to ensure needed
 'ON TRUE' occurs &  related tests

---
 sqlglot/dialects/postgres.py | 8 ++++++++
 tests/dialects/test_tsql.py  | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/sqlglot/dialects/postgres.py b/sqlglot/dialects/postgres.py
index def7631911..b6de1243d7 100644
--- a/sqlglot/dialects/postgres.py
+++ b/sqlglot/dialects/postgres.py
@@ -617,6 +617,14 @@ class Generator(generator.Generator):
             exp.JSONPathSubscript,
         }
 
+        def lateral_sql(self, expression: exp.Lateral) -> str:
+            sql = super().lateral_sql(expression)
+
+            if expression.args.get("cross_apply") is not None:
+                sql = f"{sql} ON TRUE"
+
+            return sql
+
         TYPE_MAPPING = {
             **generator.Generator.TYPE_MAPPING,
             exp.DataType.Type.TINYINT: "SMALLINT",
diff --git a/tests/dialects/test_tsql.py b/tests/dialects/test_tsql.py
index ba2f973023..32d39fa53f 100644
--- a/tests/dialects/test_tsql.py
+++ b/tests/dialects/test_tsql.py
@@ -1854,6 +1854,7 @@ def test_lateral_subquery(self):
             "SELECT x.a, x.b, t.v, t.y FROM x CROSS APPLY (SELECT v, y FROM t) t(v, y)",
             write={
                 "spark": "SELECT x.a, x.b, t.v, t.y FROM x INNER JOIN LATERAL (SELECT v, y FROM t) AS t(v, y)",
+                "postgres": "SELECT x.a, x.b, t.v, t.y FROM x INNER JOIN LATERAL (SELECT v, y FROM t) AS t(v, y) ON TRUE",
                 "tsql": "SELECT x.a, x.b, t.v, t.y FROM x CROSS APPLY (SELECT v, y FROM t) AS t(v, y)",
             },
         )
@@ -1861,6 +1862,7 @@ def test_lateral_subquery(self):
             "SELECT x.a, x.b, t.v, t.y FROM x OUTER APPLY (SELECT v, y FROM t) t(v, y)",
             write={
                 "spark": "SELECT x.a, x.b, t.v, t.y FROM x LEFT JOIN LATERAL (SELECT v, y FROM t) AS t(v, y)",
+                "postgres": "SELECT x.a, x.b, t.v, t.y FROM x LEFT JOIN LATERAL (SELECT v, y FROM t) AS t(v, y) ON TRUE",
                 "tsql": "SELECT x.a, x.b, t.v, t.y FROM x OUTER APPLY (SELECT v, y FROM t) AS t(v, y)",
             },
         )
@@ -1868,6 +1870,7 @@ def test_lateral_subquery(self):
             "SELECT x.a, x.b, t.v, t.y, s.v, s.y FROM x OUTER APPLY (SELECT v, y FROM t) t(v, y) OUTER APPLY (SELECT v, y FROM t) s(v, y) LEFT JOIN z ON z.id = s.id",
             write={
                 "spark": "SELECT x.a, x.b, t.v, t.y, s.v, s.y FROM x LEFT JOIN LATERAL (SELECT v, y FROM t) AS t(v, y) LEFT JOIN LATERAL (SELECT v, y FROM t) AS s(v, y) LEFT JOIN z ON z.id = s.id",
+                "postgres": "SELECT x.a, x.b, t.v, t.y, s.v, s.y FROM x LEFT JOIN LATERAL (SELECT v, y FROM t) AS t(v, y) ON TRUE LEFT JOIN LATERAL (SELECT v, y FROM t) AS s(v, y) ON TRUE LEFT JOIN z ON z.id = s.id",
                 "tsql": "SELECT x.a, x.b, t.v, t.y, s.v, s.y FROM x OUTER APPLY (SELECT v, y FROM t) AS t(v, y) OUTER APPLY (SELECT v, y FROM t) AS s(v, y) LEFT JOIN z ON z.id = s.id",
             },
         )
@@ -1877,6 +1880,7 @@ def test_lateral_table_valued_function(self):
             "SELECT t.x, y.z FROM x CROSS APPLY tvfTest(t.x) y(z)",
             write={
                 "spark": "SELECT t.x, y.z FROM x INNER JOIN LATERAL TVFTEST(t.x) AS y(z)",
+                "postgres": "SELECT t.x, y.z FROM x INNER JOIN LATERAL TVFTEST(t.x) AS y(z) ON TRUE",
                 "tsql": "SELECT t.x, y.z FROM x CROSS APPLY TVFTEST(t.x) AS y(z)",
             },
         )
@@ -1884,6 +1888,7 @@ def test_lateral_table_valued_function(self):
             "SELECT t.x, y.z FROM x OUTER APPLY tvfTest(t.x)y(z)",
             write={
                 "spark": "SELECT t.x, y.z FROM x LEFT JOIN LATERAL TVFTEST(t.x) AS y(z)",
+                "postgres": "SELECT t.x, y.z FROM x LEFT JOIN LATERAL TVFTEST(t.x) AS y(z) ON TRUE",
                 "tsql": "SELECT t.x, y.z FROM x OUTER APPLY TVFTEST(t.x) AS y(z)",
             },
         )
@@ -1891,6 +1896,7 @@ def test_lateral_table_valued_function(self):
             "SELECT t.x, y.z FROM x OUTER APPLY a.b.tvfTest(t.x)y(z)",
             write={
                 "spark": "SELECT t.x, y.z FROM x LEFT JOIN LATERAL a.b.tvfTest(t.x) AS y(z)",
+                "postgres": "SELECT t.x, y.z FROM x LEFT JOIN LATERAL a.b.tvfTest(t.x) AS y(z) ON TRUE",
                 "tsql": "SELECT t.x, y.z FROM x OUTER APPLY a.b.tvfTest(t.x) AS y(z)",
             },
         )