BemiDB

BemiDB is a Postgres read replica optimized for analytics. It consists of a single binary that seamlessly connects to a Postgres database, replicates the data in a compressed columnar format, and allows you to run complex queries using its Postgres-compatible analytical query engine.

Contents

• Highlights
• Use cases
• Quickstart
• Configuration
• Architecture
• Benchmark
• Data type mapping
• Future roadmap
• Alternatives
• Development
• License

Highlights

• Performance: runs analytical queries up to 2000x faster than Postgres.
• Single Binary: consists of a single binary that can be run on any machine.
• Postgres Replication: automatically syncs data from Postgres databases.
• Compressed Data: uses an open columnar format for tables with 4x compression.
• Scalable Storage: storage is separated from compute and can natively work on S3.
• Query Engine: embeds a query engine optimized for analytical workloads.
• Postgres-Compatible: integrates with any services and tools in the Postgres ecosystem.
• Open-Source: released under an OSI-approved license.

Use cases

• Run complex analytical queries like it's your Postgres database. Without worrying about performance impact and indexing.
• Simplify your data stack down to a single binary. No complex setup, no data movement, no CDC, no ETL, no DW.
• Integrate with Postgres-compatible tools and services. Query and visualize data with BI tools, notebooks, and ORMs.
• Have all data automatically synced into your data lakehouse. Using Iceberg tables with Parquet data on object storage.

Quickstart

Install BemiDB:

curl -sSL https://raw.githubusercontent.com/BemiHQ/BemiDB/refs/heads/main/scripts/install.sh | bash

Sync data from a Postgres database:

./bemidb --pg-database-url postgres://postgres:postgres@localhost:5432/dbname sync

Then run BemiDB database:

./bemidb start

Run Postgres queries on top of the BemiDB database:

# List all tables
psql postgres://localhost:54321/bemidb -c "SELECT table_schema, table_name FROM information_schema.tables"

# Query a table
psql postgres://localhost:54321/bemidb -c "SELECT COUNT(*) FROM [table_name]"

Configuration

Local disk storage

By default, BemiDB stores data on the local disk. Here is an example of running BemiDB with default settings and storing data in a local iceberg directory:

./bemidb \
  --storage-type LOCAL \
  --storage-path ./iceberg \ # $PWD/iceberg/*
  start

S3 block storage

BemiDB natively supports S3 storage. You can specify the S3 settings using the following flags:

./bemidb \
  --storage-type S3 \
  --storage-path iceberg \ # s3://[AWS_S3_BUCKET]/iceberg/*
  --aws-region [AWS_REGION] \
  --aws-s3-bucket [AWS_S3_BUCKET] \
  --aws-access-key-id [AWS_ACCESS_KEY_ID] \
  --aws-secret-access-key [AWS_SECRET_ACCESS_KEY] \
  start

Here is the minimal IAM policy required for BemiDB to work with S3:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "s3:PutObject",
                "s3:GetObject",
                "s3:ListBucket",
                "s3:DeleteObject"
            ],
            "Resource": [
                "arn:aws:s3:::[AWS_S3_BUCKET]",
                "arn:aws:s3:::[AWS_S3_BUCKET]/*"
            ]
        }
    ]
}

Periodic data sync

Sync data periodically from a Postgres database:

./bemidb \
  --pg-sync-interval 1h \
  --pg-database-url postgres://postgres:postgres@localhost:5432/dbname \
  sync

Note that incremental real-time replication is not supported yet (WIP). Please see the Future roadmap.

Syncing from selective tables

You can sync only specific tables from your Postgres database. To include specific tables during the sync:

./bemidb \
  --pg-include-tables public.users,public.transactions \
  --pg-database-url postgres://postgres:postgres@localhost:5432/dbname \
  sync

To exclude specific tables during the sync:

./bemidb \
  --pg-exclude-tables public.cache,public.logs \
  --pg-database-url postgres://postgres:postgres@localhost:5432/dbname \
  sync

Note: You cannot use --pg-include-tables and --pg-exclude-tables simultaneously.

Syncing from multiple Postgres databases

BemiDB supports syncing data from multiple Postgres databases into the same BemiDB database by allowing prefixing schemas.

For example, if two Postgres databases db1 and db2 contain public schemas, you can prefix them as follows:

./bemidb \
  --pg-schema-prefix db1_ \
  --pg-database-url postgres://postgres:postgres@localhost:5432/db1 \
  sync

./bemidb \
  --pg-schema-prefix db2_ \
  --pg-database-url postgres://postgres:postgres@localhost:5432/db2 \
  sync

Then you can query and join tables from both Postgres databases in the same BemiDB database:

./bemidb start

psql postgres://localhost:54321/bemidb -c \
  "SELECT * FROM db1_public.[TABLE] JOIN db2_public.[TABLE] ON ..."

Configuration options

sync command

CLI argument	Environment variable	Default value	Description
--pg-database-url	PG_DATABASE_URL	Required	PostgreSQL database URL to sync
--pg-sync-interval	PG_SYNC_INTERVAL		Interval between syncs. Valid units: ns, us/µs, ms, s, m, h
--pg-exclude-schemas	PG_EXCLUDE_SCHEMAS		List of schemas to exclude from sync. Comma-separated
--pg-include-schemas	PG_INCLUDE_SCHEMAS		List of schemas to include in sync. Comma-separated
--pg-exclude-tables	PG_EXCLUDE_TABLES		List of tables to exclude from sync. Comma-separated schema.table
--pg-include-tables	PG_INCLUDE_TABLES		List of tables to include in sync. Comma-separated schema.table
--pg-schema-prefix	PG_SCHEMA_PREFIX		Prefix for PostgreSQL schema names

start command

CLI argument	Environment variable	Default value	Description
--host	BEMIDB_HOST	127.0.0.1	Host for BemiDB to listen on
--port	BEMIDB_PORT	54321	Port for BemiDB to listen on
--database	BEMIDB_DATABASE	bemidb	Database name
--init-sql	BEMIDB_INIT_SQL	./init.sql	Path to the initialization SQL file
--user	BEMIDB_USER		Database user. Allows any if empty
--password	BEMIDB_PASSWORD		Database password. Allows any if empty

Other common options

CLI argument	Environment variable	Default value	Description
--storage-type	BEMIDB_STORAGE_TYPE	LOCAL	Storage type: LOCAL or S3
--storage-path	BEMIDB_STORAGE_PATH	iceberg	Path to the storage folder
--log-level	BEMIDB_LOG_LEVEL	INFO	Log level: ERROR, WARN, INFO, DEBUG, TRACE
--aws-s3-endpoint	AWS_S3_ENDPOINT	s3.amazonaws.com	AWS S3 endpoint
--aws-region	AWS_REGION	Required with S3 storage type	AWS region
--aws-s3-bucket	AWS_S3_BUCKET	Required with S3 storage type	AWS S3 bucket name
--aws-access-key-id	AWS_ACCESS_KEY_ID	Required with S3 storage type	AWS access key ID
--aws-secret-access-key	AWS_SECRET_ACCESS_KEY	Required with S3 storage type	AWS secret access key

Note that CLI arguments take precedence over environment variables. I.e. you can override the environment variables with CLI arguments.

Architecture

BemiDB consists of the following main components:

• Database Server: implements the Postgres protocol to enable Postgres compatibility.
• Query Engine: embeds the DuckDB query engine to run analytical queries.
• Storage Layer: uses the Iceberg table format to store data in columnar compressed Parquet files.
• Postgres Connector: connects to a Postgres databases to sync tables' schema and data.

Benchmark

BemiDB is optimized for analytical workloads and can run complex queries up to 2000x faster than Postgres.

On the TPC-H benchmark with 22 sequential queries, BemiDB outperforms Postgres by a significant margin:

• Scale factor: 0.1
  • BemiDB unindexed: 2.3s 👍
  • Postgres unindexed: 1h23m13s 👎 (2,170x slower)
  • Postgres indexed: 1.5s 👍 (99.97% bottleneck reduction)
• Scale factor: 1.0
  • BemiDB unindexed: 25.6s 👍
  • Postgres unindexed: ∞ 👎 (infinitely slower)
  • Postgres indexed: 1h34m40s 👎 (220x slower)

See the benchmark directory for more details.

Data type mapping

Primitive data types are mapped as follows:

PostgreSQL	Parquet	Iceberg
bool	BOOLEAN	boolean
varchar, text, bpchar, bit	BYTE_ARRAY (UTF8)	string
int2, int4	INT32	int
int8	INT64	long
xid	INT32 (UINT_32)	int
xid8	INT64 (UINT_64)	long
float4, float8	FLOAT	float
numeric	FIXED_LEN_BYTE_ARRAY (DECIMAL)	decimal(P, S)
date	INT32 (DATE)	date
time, timetz	INT64 (TIME_MICROS / TIME_MILLIS)	time
timestamp	INT64 (TIMESTAMP_MICROS / TIMESTAMP_MILLIS)	timestamp / timestamp_ns
timestamptz	INT64 (TIMESTAMP_MICROS / TIMESTAMP_MILLIS)	timestamptz / timestamptz_ns
uuid	FIXED_LEN_BYTE_ARRAY	uuid
bytea	BYTE_ARRAY (UTF8)	binary
interval	BYTE_ARRAY (UTF8)	string
point, line, lseg, box, path, polygon, circle	BYTE_ARRAY (UTF8)	string
cidr, inet, macaddr, macaddr8	BYTE_ARRAY (UTF8)	string
tsvector, xml, pg_snapshot	BYTE_ARRAY (UTF8)	string
json, jsonb	BYTE_ARRAY (UTF8)	string (JSON logical type)
_* (array)	LIST *	list
* (user-defined type)	BYTE_ARRAY (UTF8)	string

Note that Postgres json and jsonb types are implemented as JSON logical types and stored as strings (Parquet and Iceberg don't support unstructured data types). You can query JSON columns using standard operators, for example:

SELECT * FROM [TABLE] WHERE [JSON_COLUMN]->>'[JSON_KEY]' = '[JSON_VALUE]';

Future roadmap

• Incremental data synchronization into Iceberg tables.
• Support for parent partitioned tables.
• Real-time replication from Postgres using CDC.
• Direct Postgres-compatible write operations.
• Iceberg table compaction and partitioning.
• Cache layer for frequently accessed data.
• Materialized views.

Alternatives

BemiDB vs PostgreSQL

PostgreSQL pros:

• It is the most loved general-purpose transactional (OLTP) database 💛
• Capable of running analytical queries at small scale

PostgreSQL cons:

• Slow for analytical (OLAP) queries on medium and large datasets
• Requires creating indexes for specific analytical queries, which impacts the "write" performance for transactional queries
• Materialized views as a "cache" require manual maintenance and become increasingly slow to refresh as the data grows
• Further tuning may not be possible if executing various ad-hoc analytical queries

BemiDB vs PostgreSQL extensions

PostgreSQL extensions pros:

• There is a wide range of extensions available in the PostgreSQL ecosystem
• Open-source community driven

PostgreSQL extensions cons:

• Performance overhead when running analytical queries affecting transactional queries
• Limited support for installable extensions in managed PostgreSQL services (for example, AWS Aurora allowlist)
• Increased PostgreSQL maintenance complexity when upgrading versions
• Require manual data syncing and schema mapping if data is stored in a different format

Main types of extensions for analytics:

• Foreign data wrapper extensions (parquet_fdw, parquet_s3_fdw, etc.)
  • Pros: allow querying external data sources like columnar Parquet files directly from PostgreSQL
  • Cons: use not optimized for analytics query engines
• OLAP query engine extensions (pg_duckdb, pg_analytics, etc.)
  • Pros: integrate an analytical query engine directly into PostgreSQL
  • Cons: cumbersome to use (creating foreign tables, calling custom functions), data layer is not integrated and optimized

BemiDB vs DuckDB

DuckDB pros:

• Designed for OLAP use cases
• Easy to run with a single binary

DuckDB cons:

• Limited support in the data ecosystem like notebooks, BI tools, etc.
• Requires manual data syncing and schema mapping for best performance
• Limited features compared to a full-fledged database: no support for writing into Iceberg tables, reading from Iceberg according to the spec, etc.

BemiDB vs real-time OLAP databases (ClickHouse, Druid, etc.)

Real-time OLAP databases pros:

• High-performance optimized for real-time analytics

Real-time OLAP databases cons:

• Require expertise to set up and manage distributed systems
• Limitations on data mutability
• Steeper learning curve
• Require manual data syncing and schema mapping

BemiDB vs big data query engines (Spark, Trino, etc.)

Big data query engines pros:

• Distributed SQL query engines for big data analytics

Big data query engines cons:

• Complex to set up and manage a distributed query engine (ZooKeeper, JVM, etc.)
• Don't have a storage layer themselves
• Require manual data syncing and schema mapping

BemiDB vs proprietary solutions (Snowflake, Redshift, BigQuery, Databricks, etc.)

Proprietary solutions pros:

• Fully managed cloud data warehouses and lakehouses optimized for OLAP

Proprietary solutions cons:

• Can be expensive compared to other alternatives
• Vendor lock-in and limited control over the data
• Require separate systems for data syncing and schema mapping

Development

We develop BemiDB using Devbox to ensure a consistent development environment without relying on Docker.

To start developing BemiDB and run tests, follow these steps:

cp .env.sample .env
make install
make test

To run BemiDB locally, use the following command:

make up

To sync data from a Postgres database, use the following command:

make sync

License

Distributed under the terms of the AGPL-3.0 License. If you need to modify and distribute the code, please release it to contribute back to the open-source community.