From 9d654590b05280ee5e70d1746096763a44f04dab Mon Sep 17 00:00:00 2001
From: sorhawell <sorhawell@gmail.com>
Date: Sun, 12 Nov 2023 21:24:15 +0100
Subject: [PATCH 1/3] drop_all_in_place

---
 R/extendr-wrappers.R           | 2 ++
 src/rust/src/rdataframe/mod.rs | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/R/extendr-wrappers.R b/R/extendr-wrappers.R
index 209b63df3..4b5732f2e 100644
--- a/R/extendr-wrappers.R
+++ b/R/extendr-wrappers.R
@@ -129,6 +129,8 @@ DataFrame$default <- function() .Call(wrap__DataFrame__default)
 
 DataFrame$lazy <- function() .Call(wrap__DataFrame__lazy, self)
 
+DataFrame$drop_all_in_place <- function() invisible(.Call(wrap__DataFrame__drop_all_in_place, self))
+
 DataFrame$new_with_capacity <- function(capacity) .Call(wrap__DataFrame__new_with_capacity, capacity)
 
 DataFrame$set_column_from_robj <- function(robj, name) .Call(wrap__DataFrame__set_column_from_robj, self, robj, name)
diff --git a/src/rust/src/rdataframe/mod.rs b/src/rust/src/rdataframe/mod.rs
index fa63da33c..327ba3e37 100644
--- a/src/rust/src/rdataframe/mod.rs
+++ b/src/rust/src/rdataframe/mod.rs
@@ -124,6 +124,11 @@ impl DataFrame {
         LazyFrame(self.0.clone().lazy())
     }
 
+    //internal use only
+    pub fn drop_all_in_place(&mut self) {
+        *self = Self::new_with_capacity(0);
+    }
+
     //internal use
     pub fn new_with_capacity(capacity: i32) -> Self {
         let empty_series: Vec<pl::Series> = Vec::with_capacity(capacity as usize);

From 8158a53d572ecacc4dde0a845b62e8ad1404dac7 Mon Sep 17 00:00:00 2001
From: sorhawell <sorhawell@gmail.com>
Date: Sun, 12 Nov 2023 21:46:00 +0100
Subject: [PATCH 2/3] add unittest

---
 tests/testthat/test-dataframe.R | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tests/testthat/test-dataframe.R b/tests/testthat/test-dataframe.R
index a883abb67..cf1c8130b 100644
--- a/tests/testthat/test-dataframe.R
+++ b/tests/testthat/test-dataframe.R
@@ -1206,3 +1206,19 @@ test_that("transpose", {
     df_expected
   )
 })
+
+test_that("drop_all_in_place", {
+
+  # this test verifies internal function in_place drop all Series in DataFrame
+  # will not affect a fully cloned DataFrame df_clone
+
+  df_copy = df = polars::pl$DataFrame(mtcars)
+  df_clone = df$clone()
+  s = df$get_column("cyl")
+  .pr$DataFrame$drop_all_in_place(df) # we make this method and instead drop in place - level 3-5
+  expect_identical(df$shape, c(0,0))
+  expect_identical(df_copy$shape, c(0,0))
+  expect_identical(df_clone$shape, c(32,11))
+  expect_identical(s$len(), 32)
+})
+

From b2bb1d92ea3122b6976743ed094f1344acc6d554 Mon Sep 17 00:00:00 2001
From: sorhawell <sorhawell@gmail.com>
Date: Wed, 15 Nov 2023 01:14:09 +0100
Subject: [PATCH 3/3] add news + drop comment

---
 NEWS.md                         | 4 ++++
 tests/testthat/test-dataframe.R | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/NEWS.md b/NEWS.md
index 66ce5bb9c..61da6cb92 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -3,6 +3,10 @@
 ## What's changed
 
 - New methods `$write_json()` and `$write_ndjson()` for DataFrame (#502).
+- New private method `.pr$DataFrame$drop_all_in_place(df)` to drop `DataFrame` in-place,
+ to release memory without invoking gc(). However, if there are other strong references to any of
+ the underlying Series or arrow arrays, that memory will specifically not be released. This method
+ is aimed for r-polars extensions, and will be kept stable as much as possible (#504).
 
 # polars 0.10.1
 
diff --git a/tests/testthat/test-dataframe.R b/tests/testthat/test-dataframe.R
index cf1c8130b..b3c534178 100644
--- a/tests/testthat/test-dataframe.R
+++ b/tests/testthat/test-dataframe.R
@@ -1215,7 +1215,7 @@ test_that("drop_all_in_place", {
   df_copy = df = polars::pl$DataFrame(mtcars)
   df_clone = df$clone()
   s = df$get_column("cyl")
-  .pr$DataFrame$drop_all_in_place(df) # we make this method and instead drop in place - level 3-5
+  .pr$DataFrame$drop_all_in_place(df)
   expect_identical(df$shape, c(0,0))
   expect_identical(df_copy$shape, c(0,0))
   expect_identical(df_clone$shape, c(32,11))