Fix reading segments with no rows (#1438)

Fixes man-group/arcticdb-man#102
man-group · Mar 20, 2024 · 2f70374 · 2f70374
1 parent 7d57f21
commit 2f70374
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Showing 3 changed files with 15 additions and 2 deletions.
diff --git a/cpp/arcticdb/column_store/chunked_buffer.hpp b/cpp/arcticdb/column_store/chunked_buffer.hpp
@@ -271,7 +271,11 @@ class ChunkedBufferImpl {
     }
 
     [[nodiscard]] const uint8_t* data() const {
-        util::check(blocks_.size() == 1, "Taking a pointer to the beginning of a non-contiguous buffer");
+        if (blocks_.empty()) {
+            return nullptr;
+        }
+        internal::check<ErrorCode::E_ASSERTION_FAILURE>(blocks_.size() == 1,
+                                                        "Taking a pointer to the beginning of a non-contiguous buffer");
         blocks_[0]->magic_.check();
         return blocks_[0]->data();
     }

diff --git a/cpp/arcticdb/pipeline/read_frame.cpp b/cpp/arcticdb/pipeline/read_frame.cpp
@@ -626,7 +626,9 @@ class StringReducer {
         column_width_(alloc_width),
         dest_buffer_(ChunkedBuffer::presized(frame_.row_count() * column_width_)),
         dst_(dest_buffer_.data()) {
-        std::memset(dest_buffer_.data(), 0, dest_buffer_.bytes());
+        if (dest_buffer_.bytes() > 0) {
+            std::memset(dest_buffer_.data(), 0, dest_buffer_.bytes());
+        }
     }
 
     virtual void finalize() {

diff --git a/python/tests/integration/arcticdb/version_store/test_basic_version_store.py b/python/tests/integration/arcticdb/version_store/test_basic_version_store.py
@@ -1947,6 +1947,13 @@ def test_get_index(object_version_store):
     assert idx.iloc[0]["version_id"] == 0
 
 
+def test_read_empty_index(lmdb_version_store_v1):
+    lib = lmdb_version_store_v1
+    sym = "test_read_empty_index"
+    lib.write(sym, pd.DataFrame())
+    assert len(lib.read_index(sym)) == 0
+
+
 def test_snapshot_empty_segment(basic_store):
     lib = basic_store