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feat(rewrites): improve how constant sort values are dropped #11617

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7 changes: 6 additions & 1 deletion ibis/backends/sql/rewrites.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
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3 changes: 2 additions & 1 deletion ibis/backends/tests/sql/snapshots/test_sql/test_order_by/column/out.sql
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
SELECT
*
"t0"."f",
"t0"."c"
FROM "star1" AS "t0"
ORDER BY
"t0"."f" ASC
6 changes: 6 additions & 0 deletions ibis/backends/tests/sql/snapshots/test_sql/test_order_by/column_and_literal/out.sql
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
SELECT
"t0"."f",
"t0"."c"
FROM "star1" AS "t0"
ORDER BY
"t0"."f" ASC
6 changes: 6 additions & 0 deletions ibis/backends/tests/sql/snapshots/test_sql/test_order_by/column_derived/out.sql
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
SELECT
"t0"."f",
"t0"."c"
FROM "star1" AS "t0"
ORDER BY
"t0"."f" + 1 ASC
4 changes: 4 additions & 0 deletions ibis/backends/tests/sql/snapshots/test_sql/test_order_by/literal/out.sql
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
SELECT
"t0"."f",
"t0"."c"
FROM "star1" AS "t0"
4 changes: 4 additions & 0 deletions ibis/backends/tests/sql/snapshots/test_sql/test_order_by/literal_derived/out.sql
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
SELECT
"t0"."f",
"t0"."c"
FROM "star1" AS "t0"
13 changes: 12 additions & 1 deletion ibis/backends/tests/sql/snapshots/test_sql/test_order_by/random/out.sql
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Original file line number Diff line number Diff line change
@@ -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
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@cpcloud cpcloud Sep 29, 2025

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Why is there now a subquery? Is that correct?

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@NickCrews NickCrews Sep 30, 2025

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Did you see how the actual expression changed here? Before the expression was just t.order_by(ibis.random()). Now it is the more complicated t.order_by(ibis.random()).select("f", "c").order_by(ibis.random()).

This new version is equivalent to t.select("f", "c").order_by(ibis.random()) which is SELECT "t0"."f", "t0"."c" FROM "star1" AS "t0" ORDER BY RANDOM() ASC. For this simple case we could drop the internal order by, and then merge the two selects. But my initial gut reaction is that there are cases where the internal select result depends on the internal order by, and so in general we can't just drop the inner select? So in general I would say this subquery is unnecessary, but correct.

) AS "t1"
) AS "t2"
ORDER BY
RANDOM() ASC
18 changes: 18 additions & 0 deletions ibis/backends/tests/sql/snapshots/test_sql/test_order_by/random_and_column/out.sql
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Original file line number Diff line number Diff line change
@@ -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
16 changes: 16 additions & 0 deletions ibis/backends/tests/sql/snapshots/test_sql/test_order_by/random_and_literal/out.sql
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Original file line number Diff line number Diff line change
@@ -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
16 changes: 16 additions & 0 deletions ibis/backends/tests/sql/snapshots/test_sql/test_order_by/random_derived/out.sql
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Original file line number Diff line number Diff line change
@@ -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
17 changes: 14 additions & 3 deletions ibis/backends/tests/sql/test_sql.py
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Original file line number Diff line number Diff line change
Expand Up @@ -266,11 +266,22 @@ def test_aggregate(star1, expr_fn, snapshot):

@pytest.mark.parametrize(
"key",
["f", ibis.random()],
ids=["column", "random"],
[
pytest.param("f", id="column"),
pytest.param(ibis._.f + 1, id="column_derived"),
pytest.param(ibis.random(), id="random"),
pytest.param(ibis.random() + 1, id="random_derived"),
pytest.param(ibis.literal(5), id="literal"),
pytest.param(ibis.literal(5) + 1, id="literal_derived"),
pytest.param((ibis.random(), "f"), id="random_and_column"),
pytest.param((ibis.random(), ibis.literal(5)), id="random_and_literal"),
pytest.param(("f", ibis.literal(5)), id="column_and_literal"),
],
)
def test_order_by(star1, key, snapshot):
expr = star1.order_by(key)
# We are doing two order_bys to test that the rewrite that drops constant keys
# works at all levels of the expression tree.
expr = star1.order_by(key).select("f", "c").order_by(key)
snapshot.assert_match(to_sql(expr), "out.sql")


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