feat(rewrites): improve how constant sort values are dropped

Before, we only dropped constant sort values if
- it was an EXACT Literal. if it was derived, eg `ibis.literal(5) + 1`, then we wouldn't.
- if the merge_select_select decided to return the original select instead of merging them (eg because of a window function, unnest, etc), then we wouldn't see this optimization.

Author: NickCrews

ibis/backends/sql/rewrites.py

@@ -124,10 +124,15 @@ def filter_to_select(_, **kwargs):
     )
 
 
+def is_constant(value: ops.Value) -> bool:
+    return not value.relations and not value.find(ops.Impure, filter=ops.Value)
+
+
 @replace(p.Sort)
 def sort_to_select(_, **kwargs):
     """Convert a Sort node to a Select node."""
-    return Select(_.parent, selections=_.values, sort_keys=_.keys)
+    non_constant_keys = tuple(key for key in _.keys if not is_constant(key.expr))
+    return Select(_.parent, selections=_.values, sort_keys=non_constant_keys)
 
 
 @replace(p.Distinct)

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/column/out.sql

@@ -1,5 +1,6 @@
 SELECT
-  *
+  "t0"."f",
+  "t0"."c"
 FROM "star1" AS "t0"
 ORDER BY
   "t0"."f" ASC

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/column_and_literal/out.sql

@@ -0,0 +1,6 @@
+SELECT
+  "t0"."f",
+  "t0"."c"
+FROM "star1" AS "t0"
+ORDER BY
+  "t0"."f" ASC

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/column_derived/out.sql

@@ -0,0 +1,6 @@
+SELECT
+  "t0"."f",
+  "t0"."c"
+FROM "star1" AS "t0"
+ORDER BY
+  "t0"."f" + 1 ASC

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/literal/out.sql

@@ -0,0 +1,4 @@
+SELECT
+  "t0"."f",
+  "t0"."c"
+FROM "star1" AS "t0"

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/literal_derived/out.sql

@@ -0,0 +1,4 @@
+SELECT
+  "t0"."f",
+  "t0"."c"
+FROM "star1" AS "t0"

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/random/out.sql

@@ -1,5 +1,16 @@
 SELECT
   *
-FROM "star1" AS "t0"
+FROM (
+  SELECT
+    "t1"."f",
+    "t1"."c"
+  FROM (
+    SELECT
+      *
+    FROM "star1" AS "t0"
+    ORDER BY
+      RANDOM() ASC
+  ) AS "t1"
+) AS "t2"
 ORDER BY
   RANDOM() ASC

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/random_and_column/out.sql

@@ -0,0 +1,18 @@
+SELECT
+  *
+FROM (
+  SELECT
+    "t1"."f",
+    "t1"."c"
+  FROM (
+    SELECT
+      *
+    FROM "star1" AS "t0"
+    ORDER BY
+      RANDOM() ASC,
+      "t0"."f" ASC
+  ) AS "t1"
+) AS "t2"
+ORDER BY
+  RANDOM() ASC,
+  "t2"."f" ASC

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/random_and_literal/out.sql

@@ -0,0 +1,16 @@
+SELECT
+  *
+FROM (
+  SELECT
+    "t1"."f",
+    "t1"."c"
+  FROM (
+    SELECT
+      *
+    FROM "star1" AS "t0"
+    ORDER BY
+      RANDOM() ASC
+  ) AS "t1"
+) AS "t2"
+ORDER BY
+  RANDOM() ASC

ibis/backends/tests/sql/snapshots/test_sql/test_order_by/random_derived/out.sql

@@ -0,0 +1,16 @@
+SELECT
+  *
+FROM (
+  SELECT
+    "t1"."f",
+    "t1"."c"
+  FROM (
+    SELECT
+      *
+    FROM "star1" AS "t0"
+    ORDER BY
+      RANDOM() + 1 ASC
+  ) AS "t1"
+) AS "t2"
+ORDER BY
+  RANDOM() + 1 ASC