Release the GIL during parallel writes to avoid deadlock

Author: Alex Seaton

cpp/arcticdb/version/local_versioned_engine.cpp

@@ -1020,6 +1020,7 @@ void LocalVersionedEngine::write_parallel_frame(
     bool validate_index,
     bool sort_on_index,
     const std::optional<std::vector<std::string>>& sort_columns) const {
+    py::gil_scoped_release release_gil;
     WriteIncompleteOptions options{
         .validate_index=validate_index,
         .write_options=get_write_options(),

python/tests/unit/arcticdb/version_store/test_write.py

@@ -8,8 +8,9 @@
 import numpy as np
 import pandas as pd
 import pytest
-from arcticdb.exceptions import SortingException, NormalizationException
+from arcticdb.exceptions import SortingException
 from arcticdb.util._versions import IS_PANDAS_TWO
+from arcticdb.util.test import assert_frame_equal
 from pandas import MultiIndex
 
 
@@ -133,3 +134,28 @@ def test_write_non_timestamp_index(lmdb_version_store, index_type, sorted, valid
     assert info["sorted"] == "UNKNOWN"
 
 
+def test_write_unicode(lmdb_version_store):
+    symbol = "test_write_unicode"
+    uc = "\u0420\u043e\u0441\u0441\u0438\u044f"
+
+    df1 = pd.DataFrame(
+        index=[pd.Timestamp("2018-01-02"), pd.Timestamp("2018-01-03")],
+        data={"a": ["123", uc]},
+    )
+    lmdb_version_store.write(symbol, df1)
+    vit = lmdb_version_store.read(symbol)
+    assert_frame_equal(vit.data, df1)
+
+
+def test_write_parallel_unicode(lmdb_version_store):
+    symbol = "test_write_parallel_unicode"
+    uc = "\u0420\u043e\u0441\u0441\u0438\u044f"
+
+    df1 = pd.DataFrame(
+        index=[pd.Timestamp("2018-01-02"), pd.Timestamp("2018-01-03")],
+        data={"a": ["123", uc]},
+    )
+    lmdb_version_store.write(symbol, df1, parallel=True)
+    lmdb_version_store.compact_incomplete(symbol, append=False, convert_int_to_float=False)
+    vit = lmdb_version_store.read(symbol)
+    assert_frame_equal(vit.data, df1)