DuckDB

• duckdb/duckdb
  • MIT, C++
  • 嵌入式 OLAP 数据库
  • 类似 SQLite - 但列存储，面向分析
  • 支持查询 Parquet, CSV
  • 向量引擎，并行查询
  • 官方支持 SDK: Python, Java, C++, NodeJS, R
  • 语法类似 pg - 使用 libpg_query
• 参考
  • duckdb/pg_duckdb
    • 作为 PG 插件使用 DuckDB
    • supabase/postgres#1106
  • duckdb/duckdb-wasm
    • 在 Web 内执行，基于 FS API 进行 IO 交互
  • https://news.ycombinator.com/item?id=32684424
  • https://h2oai.github.io/db-benchmark/
  • duckdblabs/arrow
    • Arrow - Python Binding
  • evanwashere/duckdb
    • bun binding

caution

• 不能更新 unique 列 #5771

note

• upsert 0.6.2
  • 支持 insert or replace/ignore
  • 支持 on conflict

# by Homebre
brew install duckdb
# by Download
curl -LO https://ghproxy.com/github.com/duckdb/duckdb/releases/download/v0.8.0/duckdb_cli-osx-universal.zip
unzip duckdb_cli-osx-universal.zip
./duckdb

SELECT * FROM 'myfile.csv';
SELECT * FROM 'myfile.parquet';

-- csv, parquet
SELECT * FROM 'https://domain.tld/file.extension';

-- S3
SET s3_region='us-east-1';
SET s3_endpoint='<domain>.<tld>:<port>';
SET s3_url_style='path';
SET s3_access_key_id='<AWS access key id>';
SET s3_secret_access_key='<AWS secret access key>';
SET s3_session_token='<AWS session token>';
SELECT * FROM 's3://bucket/file.extension';

SELECT * FROM parquet_scan('s3://bucket/*.parquet');
SELECT COUNT(*) FROM parquet_scan('s3://bucket/folder*/100?/t[0-9].parquet');
SELECT * FROM parquet_scan('s3://bucket/*.parquet', FILENAME = 1);
SELECT * FROM parquet_scan('s3://bucket/*/file.parquet', HIVE_PARTITIONING = 1);

-- s3_uploader_max_parts_per_file, s3_uploader_max_filesize, s3_uploader_thread_limit
COPY table_name TO 's3://bucket/file.extension';

-- SQLite
CALL sqlite_attach('data.db');
PRAGMA show_tables;

-- PostgreSQL
-- connect string
CALL POSTGRES_ATTACH('');
SELECT * FROM POSTGRES_SCAN('', 'public', 'mytable');

-- CSV
SELECT * FROM read_csv_auto('test.csv');
-- HEADER=TRUE
-- read_csv_auto -> read_csv(AUTO_DETECT=TRUE)
SELECT * FROM read_csv_auto('test.csv', SAMPLE_SIZE=20000);
-- 导入
CREATE TABLE ontime AS SELECT * FROM read_csv_auto('test.csv');
-- 也可以先创建表再通过 COPY 导入
COPY ontime FROM 'test.csv' ( DELIMITER '|', HEADER, AUTO_DETECT TRUE );

-- PARQUET
SELECT * FROM parquet_scan('test.parquet');
SELECT * FROM 'test.parquet';
-- 多文件
SELECT * FROM parquet_scan('test/*.parquet');
-- 不导入但也提供查询
CREATE VIEW people AS SELECT * FROM parquet_scan('test.parquet');
-- 导入带压缩
COPY tbl TO 'result-zstd.parquet' (FORMAT 'PARQUET', CODEC 'ZSTD')

-- 导出表 - 可以 FORMAT PARQUET
COPY lineitem TO 'lineitem.tbl' ( DELIMITER '|', HEADER );
COPY lineitem(l_orderkey) TO 'orderkey.tbl' ( DELIMITER '|' );
COPY (SELECT 42 AS a, 'hello' AS b) TO 'query.csv' WITH (HEADER 1, DELIMITER ',');

-- 导出数据库
-- 导出到目录
EXPORT DATABASE 'target_directory';
-- 导出 CSV
EXPORT DATABASE 'target_directory' (FORMAT CSV, DELIMITER '|');
-- 导出 parquet 格式
EXPORT DATABASE 'target_directory' (FORMAT PARQUET);
-- 导入
IMPORT DATABASE 'target_directory'

Inspect

PRAGMA storage_info('table_name');

SELECT * EXCLUDE (column_path, segment_id, start, stats, persistent, block_id, block_offset, has_updates)
FROM pragma_storage_info('names') USING SAMPLE 10 ROWS
ORDER BY row_group_id;

extension

select * from duckdb_extensions();

install 'fts';
load 'fts';

-- 下载 http://extensions.duckdb.org/v0.6.1/osx_amd64/httpfs.duckdb_extension.gz
-- 本地 ~/.duckdb/extensions/v0.6.1/osx_amd64/httpfs.duckdb_extension
install 'httpfs';
load 'httpfs';

• 不支持代理 https://github.com/duckdb/duckdb/issues/3836

ver=$(duckdb -version | cut -d ' ' -f 1)
mkdir -p ~/.duckdb/extensions/$ver/osx_amd64
cd ~/.duckdb/extensions/$ver/osx_amd64

# https://duckdb.org/docs/extensions/overview
for name in httpfs excel fts sqlite_scanner postgres_scanner json parquet jemalloc; do
  [ -e $name.duckdb_extension ] && continue
  echo Installing $name
  curl -LO http://extensions.duckdb.org/$ver/osx_amd64/$name.duckdb_extension.gz
  gzip -d $name.duckdb_extension.gz
done

load 'jemalloc';
load 'json';
load 'postgres_scanner';
load 'sqlite_scanner';

• sqlite_scanner
  • sqlite_attach('data.sqlite') - 创建 view - 只能查 不能写
  • sqlite_scan - SELECT * FROM sqlite_scan('data.sqlite', 'tab'); - 直接查询单个表
• wasm
• visualizer
  • 测试结果 -> HTML
  • pragma visualize_last_profiling_output('__TEST_DIR__/test.html')
• sqlsmith
  • SQL 生成器，用于测试
• tpch
• tpcds

FAQ

duckdb vs SQLite3

-	duckdb	SQLite
Since	2018	2000-08-17
架构	列存	行存
场景	OLAP	OLTP
语言	C++	C
多线程访问	❌	✅
生态	⭐️	⭐️⭐️⭐️
成熟	⭐️	⭐️⭐️⭐️
并发	MVCC	fs lock
Native JSON	✅	❌

• https://duckdb.org/why_duckdb.html