From eb5f6740b37739d4508872715bc8d403666d288f Mon Sep 17 00:00:00 2001
From: Phillip Cloud <417981+cpcloud@users.noreply.github.com>
Date: Thu, 19 Sep 2024 06:27:46 -0400
Subject: [PATCH] fix(polars): use double explode -> implode hack to flatten

---
 ibis/backends/polars/compiler.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/ibis/backends/polars/compiler.py b/ibis/backends/polars/compiler.py
index 7bc9c9f147152..20f5ff15749ba 100644
--- a/ibis/backends/polars/compiler.py
+++ b/ibis/backends/polars/compiler.py
@@ -1021,7 +1021,11 @@ def array_flatten(op, **kw):
         .then(None)
         .when(result.list.len() == 0)
         .then([])
-        .otherwise(result.flatten())
+        # polars doesn't have an efficient API (yet?) for removing one level of
+        # nesting from an array so we use elementwise evaluation
+        #
+        # https://github.com/ibis-project/ibis/issues/10135
+        .otherwise(result.list.eval(pl.element().flatten()))
     )