Fix: don't evaluate Rand twice when ordering by it (#3233)

tobymao · Mar 27, 2024 · fd5783f · fd5783f
1 parent 8325039
commit fd5783f
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Showing 2 changed files with 10 additions and 1 deletion.
diff --git a/sqlglot/generator.py b/sqlglot/generator.py
@@ -2091,7 +2091,7 @@ def ordered_sql(self, expression: exp.Ordered) -> str:
                     self.unsupported(
                         f"'{nulls_sort_change.strip()}' translation not supported with positional ordering"
                     )
-                else:
+                elif not isinstance(expression.this, exp.Rand):
                     null_sort_order = " DESC" if nulls_sort_change == " NULLS FIRST" else ""
                     this = f"CASE WHEN {this} IS NULL THEN 1 ELSE 0 END{null_sort_order}, {this}"
                 nulls_sort_change = ""

diff --git a/tests/dialects/test_postgres.py b/tests/dialects/test_postgres.py
@@ -310,6 +310,15 @@ def test_postgres(self):
         )
         self.validate_identity("SELECT * FROM t1*", "SELECT * FROM t1")
 
+        self.validate_all(
+            'SELECT * FROM "test_table" ORDER BY RANDOM() LIMIT 5',
+            write={
+                "bigquery": "SELECT * FROM `test_table` ORDER BY RAND() NULLS LAST LIMIT 5",
+                "duckdb": 'SELECT * FROM "test_table" ORDER BY RANDOM() LIMIT 5',
+                "postgres": 'SELECT * FROM "test_table" ORDER BY RANDOM() LIMIT 5',
+                "tsql": "SELECT TOP 5 * FROM [test_table] ORDER BY RAND()",
+            },
+        )
         self.validate_all(
             "SELECT (data -> 'en-US') AS acat FROM my_table",
             write={