sgilmore10 commented on code in PR #668:
URL: https://github.com/apache/arrow-site/pull/668#discussion_r2210812417
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_posts/2025-07-16-21.0.0-release.md:
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+---
+layout: post
+title: "Apache Arrow 21.0.0 Release"
+date: "2025-07-16 00:00:00"
+author: pmc
+categories: [release]
+---
+<!--
+{% comment %}
+Licensed to the Apache Software Foundation (ASF) under one or more
+contributor license agreements. See the NOTICE file distributed with
+this work for additional information regarding copyright ownership.
+The ASF licenses this file to you under the Apache License, Version 2.0
+(the "License"); you may not use this file except in compliance with
+the License. You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+{% endcomment %}
+-->
+
+The Apache Arrow team is pleased to announce the 21.0.0 release. This release
+covers over 2 months of development work and includes [**1234 resolved
+issues**][1] on [**1234 distinct commits**][2] from [**1234 distinct
+contributors**][2]. See the [Install Page](https://arrow.apache.org/install/)
to
+learn how to get the libraries for your platform.
+
+The release notes below are not exhaustive and only expose selected highlights
+of the release. Many other bugfixes and improvements have been made: we refer
+you to the [complete changelog][3].
+
+## Community
+
+Since the 20.0.0 release, Alenka Frim has been invited to join the Project
+Management Committee (PMC).
+
+Thanks for your contributions and participation in the project!
+
+## Release Highlights
+
+## Columnar Format
+
+## Arrow Flight RPC Notes
+
+## C++ Notes
+
+### Acero
+
+### Compute
+
+The Cast function is now able to reorder fields when casting from one
+struct type to another; the fields are matched by name, not by index
(GH-45028).
+
+Many compute kernels have been moved into a separate, optional, shared library
+(GH-25025). This allows reducing the Arrow C++ distribution size when the
+compute functionality is not being used by the application. Note that some
+compute functions, such as the Cast function, will still be built for internal
+use in various Arrow components.
+
+Better half-float support has been added to some compute functions:
+`is_nan`, `is_inf`, `is_finite`, `negate`, `negate_checked`, `sign` (GH-45083);
+`if_else`, `case_when`, `coalesce`, `choose`, `replace_with_mask`,
`fill_null_forward`,
+`fill_null_backward` (GH-37027); `run_end_encode`, `run_end_decode` (GH-46285).
+
+Better decimal32 and decimal64 support has been added to some compute
functions:
+`run_end_encode`, `run_end_decode` (GH-46285).
+
+A new function `utf8_zero_fill` acts like Python's `str.zfill` method by
providing
+a left-padding function that preserves the optional leading plus/minus sign
(GH-46683).
+
+Decimal sum aggregation now produces a decimal result with an increased
precision
+in order to reduce the risk of overflowing the result type (GH-35166).
+
+### CSV
+
+Reading Duration columns is now supported (GH-40278).
+
+### Dataset
+
+It is now possible to preserve order when writing a dataset multi-threaded.
+The feature is disabled by default (GH-26818).
+
+### Filesystems
+
+The S3 filesystem can optionally be built into a separate DLL (GH-40343).
+
+### Parquet
+
+#### Encryption
+
+A new `SecureString` class must now be used to communicate sensitive data
(such as
+secret keys) with Parquet encryption APIs. This class automatically wipes its
+contents from memory when destroyed, unlike regular `std::string` (GH-31603).
+
+#### Type support
+
+The new VARIANT logical type is supported at a low level, and an extension type
+`parquet.variant` is added to reflect such columns when reading them to Arrow
+(GH-45937).
+
+The UUID logical type is automatically converted to/from the `arrow.uuid`
+canonical extension type when reading or writing Parquet data, respectively.
+
+The GEOMETRY and GEOGRAPHY logical types are supported (GH-45522). They are
+automatically converted to/from the corresponding GeoArrow extension type,
+if it has been registered by GeoArrow. Geospatial column statistics are also
+supported.
+
+It is now possible to read BYTE_ARRAY columns directly as LargeBinary or
BinaryView,
+without any intermediate conversion from Binary. Similarly, those types can be
+written directly to Parquet (GH-43041). This allows bypassing the 2 GiB data
+per chunk limitation of the Binary type, and can also improve performance.
+This also applies to String types when a Parquet column has the STRING logical
type.
+
+Similarly, LIST columns can now be read directly as LargeList rather than List.
+This allows bypassing the 2^31 values per chunk limitation of regular List
types
+(GH-46676).
+
+#### Other Parquet improvements
+
+A new feature named Content-Defined Chunking improves deduplication of Parquet
+files with mostly identical contents, by choosing data page boundaries based on
+actual contents rather than a number of values. For that, it uses a rolling
hash
+function, and the min and max chunk size can be chosen. The feature is
disabled by
+default and can be enabled on a per-file basis in the Parquet
`WriterProperties`
+(GH-45750).
+
+The `EncodedStatistics` of a column chunk are publicly exposed in
`ColumnChunkMetaData`
+and can be read faster than if decoded as `Statistics` (GH-46462).
+
+SIMD optimizations for the BYTE_STREAM_SPLIT have been improved (GH-46788).
+
+Reading FIXED_LEN_BYTE_ARRAY data has been made significantly faster (up to 3x
+faster on some benchmarks). This benefits logical types such as FLOAT16
(GH-43891).
+
+### Miscellaneous C++ changes
+
+The `ARROW_USE_PRECOMPILED_HEADERS` build option was removed, as
`CMAKE_UNITY_BUILD`
+usually provides more benefits while requiring less maintenance.
+
+New data creation helpers `ArrayFromJSONString`, `ChunkedArrayFromJSONString`,
+`DictArrayFromJSONString`, `ScalarFromJSONString` and
`DictScalarFromJSONString`
+are now exposed publicly. While not as high-performing as `BufferBuilder` and
+the concrete `ArrayBuilder` subclasses, they allow easy creation of test
+or example data, for example:
+```c++
+ ARROW_ASSIGN_OR_RAISE(
+ auto string_array,
+ arrow::ArrayFromJSONString(arrow::utf8(), R"(["Hello", "World",
null])"));
+ ARROW_ASSIGN_OR_RAISE(
+ auto list_array,
+ arrow::ArrayFromJSONString(arrow::list(arrow::int32()),
+ "[[1, null, 2], [], [3]]"));
+```
+
+Some APIs were changed to accept `std::string_view` instead of `const
std::string&`.
+Most uses of those APIs should not be affected (GH-46551).
+
+A new pretty-print option allows limiting element size when printing string
+or binary data (GH-46403).
+
+It is now possible to export `Tensor` data using
+[DLPack](https://dmlc.github.io/dlpack/latest/) (GH-39294).
+
+Half-float arrays can be properly diff'ed and pretty-printed (GH-36753).
+
+Some header files in `arrow/util` that were not supposed to be exposed are
+now made internal (GH-46459).
+
+## C# Notes
+
+- TODO: Note about future repo move plan. "This is the final release of the C#
implementation of Arrow as part of the monorepo...etc.
+
+## Java, JavaScript, Go, and Rust Notes
+
+The Java, JavaScript, Go, and Rust Go projects have moved to separate
repositories outside
+the main Arrow [monorepo](https://github.com/apache/arrow).
+
+- For notes on the latest release of the [Java
+implementation](https://github.com/apache/arrow-java), see the latest [Arrow
+Java changelog][7].
+- For notes on the latest release of the [JavaScript
+implementation](https://github.com/apache/arrow-js), see the latest [Arrow
+JavaScript changelog][8].
+- For notes on the latest release of the [Rust
+ implementation](https://github.com/apache/arrow-rs) see the latest [Arrow
Rust
+ changelog][5].
+- For notes on the latest release of the [Go
+implementation](https://github.com/apache/arrow-go), see the latest [Arrow Go
+changelog][6].
+
+## Linux Packaging Notes
+
+## Python Notes
Review Comment:
```suggestion
## MATLAB Notes
### New Features
Added support for creating an `arrow.tabular.Tabule` from a list of
`arrow.tabular.RecordBatch` instances
([GH-46877](https://github.com/apache/arrow/issues/46877))
### Packaging
The MLTBX available in apache/arrow's GitHub Releases area was built against
MATLAB R2025a.
## Python Notes
```
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