[arrow] branch master updated: ARROW-9037: [C++] C-ABI: do not error out when importing array with null_count == -1

[fs...@apache.org]

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fsaintjacques pushed a commit to branch master
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The following commit(s) were added to refs/heads/master by this push:
     new 7328658  ARROW-9037: [C++] C-ABI: do not error out when importing array with null_count == -1
7328658 is described below

commit 7328658fa897ab9fbefba66344dae89a77e9c12f
Author: Zhuo Peng <18...@users.noreply.github.com>
AuthorDate: Sun Jun 7 07:53:12 2020 -0400

    ARROW-9037: [C++] C-ABI: do not error out when importing array with null_count == -1
    
    Also when exporting an array, force compute the null count. This way future version will be able to import an array exported by 0.17, and vice versa.
    
    Closes #7353 from brills/c_api_fix
    
    Authored-by: Zhuo Peng <18...@users.noreply.github.com>
    Signed-off-by: François Saint-Jacques <fs...@gmail.com>
---
 cpp/src/arrow/c/bridge.cc      |  4 +++-
 cpp/src/arrow/c/bridge_test.cc | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/cpp/src/arrow/c/bridge.cc b/cpp/src/arrow/c/bridge.cc
index c13b7a9..e6549d7 100644
--- a/cpp/src/arrow/c/bridge.cc
+++ b/cpp/src/arrow/c/bridge.cc
@@ -503,6 +503,8 @@ void ReleaseExportedArray(struct ArrowArray* array) {
 
 struct ArrayExporter {
   Status Export(const std::shared_ptr<ArrayData>& data) {
+    // Force computing null count.
+    data->GetNullCount();
     // Store buffer pointers
     export_.buffers_.resize(data->buffers.size());
     std::transform(data->buffers.begin(), data->buffers.end(), export_.buffers_.begin(),
@@ -1401,7 +1403,7 @@ struct ArrayImporter {
 
   Status ImportNullBitmap(int32_t buffer_id = 0) {
     RETURN_NOT_OK(ImportBitsBuffer(buffer_id));
-    if (data_->null_count != 0 && data_->buffers[buffer_id] == nullptr) {
+    if (data_->null_count > 0 && data_->buffers[buffer_id] == nullptr) {
       return Status::Invalid(
           "ArrowArray struct has null bitmap buffer but non-zero null_count ",
           data_->null_count);
diff --git a/cpp/src/arrow/c/bridge_test.cc b/cpp/src/arrow/c/bridge_test.cc
index 53e4ac1..33d49cc 100644
--- a/cpp/src/arrow/c/bridge_test.cc
+++ b/cpp/src/arrow/c/bridge_test.cc
@@ -2574,6 +2574,18 @@ TEST_F(TestArrayRoundtrip, Primitive) {
   TestWithJSONSliced(int32(), "[4, 5, 6, null]");
 }
 
+TEST_F(TestArrayRoundtrip, UnknownNullCount) {
+    TestWithArrayFactory([](std::shared_ptr<Array>* arr) -> Status {
+    *arr = ArrayFromJSON(int32(), "[0, 1, 2]");
+    if ((*arr)->null_bitmap()) {
+      return Status::Invalid("Failed precondition: "
+                             "the array shouldn't have a null bitmap.");
+    }
+    (*arr)->data()->SetNullCount(kUnknownNullCount);
+    return Status::OK();
+    });
+}
+
 TEST_F(TestArrayRoundtrip, Nested) {
   TestWithJSON(list(int32()), "[]");
   TestWithJSON(list(int32()), "[[4, 5], [6, null], null]");