This is based on https://github.com/MariaDB/server/pull/4830.

DuckDB Storage Engine for MariaDB

Overview

This PR introduces DuckDB 1.3.2 as an embedded analytical (OLAP) storage engine plugin for MariaDB 12.3. The engine is ported from AliSQL's DuckDB integration and fully adapted to MariaDB's handler API, plugin system, build infrastructure, and packaging conventions. It ships as a loadable module (_{ha_duckdb.so}) for *x86_64* and *ARM64* architectures.

Architecture

The engine is structured as a git submodule at [storage/duckdb/duckdb](cci:9://file:///git/mdb-12/storage/duckdb/duckdb:0:0-0:0) (repo: _{drrtuy/duckdb-engine}), which itself contains a nested submodule (_{third_parties/duckdb}) pointing to a DuckDB 1.3.2 fork with MariaDB-specific patches (e.g. _{octet_length} VARCHAR overload). DuckDB is built statically with all builtin extensions (ICU, JSON, Parquet, jemalloc, etc.) and linked into a single _{ha_duckdb.so} plugin. A debug-STL ABI mismatch guard (_{-U_GLIBCXX_DEBUG -U_GLIBCXX_ASSERTIONS}) is applied in debug builds to prevent _SIGSEGV from `sizeof(std::vector)` divergence between the plugin and the server.

Supported Operations

• *DDL:* _{CREATE TABLE}, _{DROP TABLE}, _{ALTER TABLE}, _{RENAME TABLE} — SQL is translated from MariaDB's internal structures to DuckDB-dialect DDL via [ddl_convertor.cc](cci:7://file:///git/mdb-12/storage/duckdb/duckdb/ddl_convertor.cc:0:0-0:0), including expression defaults, column types, and engine conversions (`ALTER TABLE ... ENGINE=DuckDB`).
• *DML — INSERT:* Batch ingestion through DuckDB's Appender API with delta temp tables ([delta_appender.cc](cci:7://file:///git/mdb-12/storage/duckdb/duckdb/delta_appender.cc:0:0-0:0)), supporting all major MariaDB column types.
• *DML — SELECT:* Full query pushdown to DuckDB via MariaDB's `select_handler` interface ([ha_duckdb_pushdown.cc](cci:7://file:///git/mdb-12/storage/duckdb/duckdb/ha_duckdb_pushdown.cc:0:0-0:0)), with result-set conversion back to MariaDB row format ([duckdb_select.cc](cci:7://file:///git/mdb-12/storage/duckdb/duckdb/duckdb_select.cc:0:0-0:0)).
• *DML — UPDATE/DELETE:* Direct UPDATE and DELETE translated to DuckDB SQL ([dml_convertor.cc](cci:7://file:///git/mdb-12/storage/duckdb/duckdb/dml_convertor.cc:0:0-0:0)).
• *Configuration:* DuckDB-specific server variables — memory limit, thread count, operating mode, etc. ([duckdb_config.cc](cci:7://file:///git/mdb-12/storage/duckdb/duckdb/duckdb_config.cc:0:0-0:0)).
• *Timezone & Charset:* Mapping between MariaDB and DuckDB timezone names and charset/collation conventions.
• *UDFs:* Registration of DuckDB-side user-defined functions accessible from MariaDB.
• *Per-thread context:* `DuckdbThdContext` managed via `thd_get_ha_data`/`thd_set_ha_data` (replacing AliSQL's `THD::get_duckdb_context()`).

Packaging

• New Debian package `mariadb-plugin-duckdb` for `amd64` and `arm64`.
• `postinst` / `prerm` hooks automatically run `install.sql` / `uninstall.sql` to register or unregister the plugin when the server is running.
• `PLUGIN_DUCKDB=NO` by default in native Debian builds (`debian/rules`); enabled automatically by `autobake-deb.sh` for MariaDB.org release builds when the submodule is present.
• RPM packaging scaffolding included in the submodule.

Testing

An MTR test suite is included under `mysql-test/plugin/duckdb/` covering DDL, DML, type conversions, ALTER operations, and basic query pushdown scenarios. A `disable.def` file documents tests that are not yet passing or are intentionally skipped.

Key Differences from AliSQL Port

• Removed MySQL 8 Data Dictionary (`dd::Table`, `dd::Schema`) dependency — table metadata comes from `TABLE*` and `.frm` / `TABLE_SHARE`.
• Replaced `mysql_declare_plugin` with `maria_declare_plugin`.
• Adapted all handler method signatures (no `dd::Table*` parameters).
• Removed partition support, replication batch mode (GTID batch, multi-trx), and `Relay_log_info` extensions (not applicable to MariaDB).
• Uses `DB_TYPE_AUTOASSIGN` instead of the AliSQL-specific `DB_TYPE_DUCKDB` enum.