rustream

Bidirectional Postgres sync tool. Reads tables from Postgres and writes Parquet/Iceberg files to local disk or S3, or ingests Parquet/CSV files from local disk or S3 back into Postgres. Supports incremental sync via watermark tracking and upsert-based ingestion.

Installation

From PyPI

pipx install rustream
# or
pip install rustream

From source

git clone https://github.com/kraftaa/rustream.git
cd rustream
cargo build --release
# binary is at target/release/rustream

With maturin (local dev)

pip install maturin
maturin develop --release
# now `rustream` is on your PATH

Usage

Sync (Postgres → Parquet/S3)

# Copy and edit the example config
cp config.example.yaml config.yaml

# Preview what will be synced (no files written)
rustream sync --config config.yaml --dry-run

# Run sync
rustream sync --config config.yaml

Ingest (S3/local → Postgres)

# Preview what would be ingested
rustream ingest --config ingest_config.yaml --dry-run

# Run ingest
rustream ingest --config ingest_config.yaml

Enable debug logging with RUST_LOG:

RUST_LOG=rustream=debug rustream sync --config config.yaml
RUST_LOG=rustream=debug rustream ingest --config ingest_config.yaml

Configuration

Specific tables (recommended)

postgres:
  host: localhost
  database: mydb
  user: postgres
  password: secret

output:
  type: local
  path: ./output

tables:
  - name: users
    incremental_column: updated_at
    incremental_tiebreaker_column: id
    columns:          # optional: pick specific columns
      - id
      - email
      - created_at
      - updated_at

  - name: orders
    incremental_column: updated_at
    incremental_tiebreaker_column: id

  - name: products    # no incremental_column = full sync every run

  - name: events      # append-only example (no updated_at)
    incremental_column: id
    incremental_column_is_unique: true

All tables (auto-discover)

Omit tables to sync every table in the schema. Use exclude to skip some:

postgres:
  host: localhost
  database: mydb
  user: postgres

output:
  type: local
  path: ./output

# schema: public    # default
exclude:
  - schema_migrations
  - ar_internal_metadata

S3 output

output:
  type: s3
  bucket: my-data-lake
  prefix: raw/postgres
  region: us-east-1

AWS credentials come from environment variables, ~/.aws/credentials, or IAM role.

Iceberg output

output:
  type: s3
  bucket: my-data-lake
  prefix: warehouse
  region: us-east-1

format: iceberg
warehouse: s3://my-data-lake/warehouse
catalog:
  type: filesystem    # or "glue" (requires --features glue)
  # glue_database: my_db  # required when type=glue

Ingest (S3 → Postgres)

postgres:
  host: localhost
  database: mydb
  user: postgres
  password: secret

ingest:
  input:
    type: s3
    bucket: my-data-lake
    prefix: raw/postgres/
    region: us-east-1
    pattern: "**/*.parquet"

  file_format: parquet       # "parquet" or "csv"
  write_mode: upsert         # "insert" | "upsert" | "truncate_insert"
  batch_size: 5000
  target_schema: public

  tables:
    - file_pattern: "users/*.parquet"
      target_table: users
      key_columns: [id]
      create_if_missing: true

    - file_pattern: "orders/*.parquet"
      target_table: orders
      key_columns: [id]

Ingest from local files

ingest:
  input:
    type: local
    path: ./parquet_files
    pattern: "**/*.parquet"

  file_format: parquet
  write_mode: insert
  batch_size: 5000

If no tables are listed, the target table name is inferred from the parent directory or filename.

Config reference (sync)

Field	Description
postgres.host	Postgres host
postgres.port	Postgres port (default: 5432)
postgres.database	Database name
postgres.user	Database user
postgres.password	Database password (optional)
output.type	local or s3
output.path	Local directory for Parquet files (when type=local)
output.bucket	S3 bucket (when type=s3)
output.prefix	S3 key prefix (when type=s3)
output.region	AWS region (when type=s3, optional)
batch_size	Rows per Parquet file (default: 10000)
state_dir	Directory for SQLite watermark state (default: .rustream_state)
schema	Schema to discover tables from (default: public)
exclude	List of table names to skip when using auto-discovery
tables[].name	Table name
tables[].schema	Schema name (default: public)
tables[].columns	Columns to sync (default: all)
tables[].incremental_column	Column for watermark-based incremental sync
tables[].incremental_tiebreaker_column	Stable cursor column for duplicate-safe incremental paging (required when incremental_column is set; recommended: primary key)
tables[].incremental_column_is_unique	Allow watermark-only incremental mode when incremental column is strictly unique/monotonic (e.g. append-only id)
tables[].partition_by	Partition output files: date, month, or year
format	Output format: parquet (default) or iceberg
warehouse	Warehouse path for Iceberg (required when format=iceberg)
catalog.type	Iceberg catalog: filesystem (default) or glue

Config reference (ingest)

Field	Description
ingest.input.type	local or s3
ingest.input.path	Local directory (when type=local)
ingest.input.bucket	S3 bucket (when type=s3)
ingest.input.prefix	S3 key prefix (when type=s3)
ingest.input.region	AWS region (when type=s3, optional)
ingest.input.pattern	Glob pattern for file matching (default: **/*.parquet)
ingest.file_format	parquet (default) or csv
ingest.write_mode	insert (default), upsert, or truncate_insert
ingest.batch_size	Rows per INSERT statement (default: 5000)
ingest.target_schema	Postgres schema for target tables (default: public)
ingest.tables[].file_pattern	Glob pattern to match files to this table
ingest.tables[].target_table	Postgres table to write to
ingest.tables[].key_columns	Primary key columns (required for upsert mode)
ingest.tables[].create_if_missing	Auto-CREATE TABLE from file schema (default: false)

Running Integration Tests

Some DB-backed tests are optional and run only when RUSTREAM_IT_DB_URL is set. Without this env var, those tests no-op/return early.

export RUSTREAM_IT_DB_URL="host=localhost port=5432 dbname=mydb user=postgres password=secret"
cargo test

How it works

Sync (Postgres → Parquet)

1. Connects to Postgres and introspects each table's schema via information_schema
2. Maps Postgres column types to Arrow types automatically
3. Reads rows in batches, converting to Arrow RecordBatches
4. Writes each batch as a Snappy-compressed Parquet file
5. Tracks the high watermark (max value of incremental_column) and optional cursor in local SQLite
6. Checkpoints incremental progress after each successfully written batch
7. On next run, reads rows after the saved (watermark, cursor) position

Tables without incremental_column do a full sync every run.

Ingest (Parquet/CSV → Postgres)

1. Discovers files matching the glob pattern from local disk or S3
2. Skips files already ingested (tracked in local SQLite)
3. Reads each file into Arrow RecordBatches (Parquet or CSV with schema inference)
4. Creates the target table if create_if_missing: true (DDL from Arrow schema)
5. Writes rows via multi-row parameterized INSERT or INSERT...ON CONFLICT (upsert)
6. Marks each file as ingested in SQLite to avoid reprocessing on next run

Supported Postgres types

Postgres	Arrow
boolean	Boolean
smallint	Int16
integer, serial	Int32
bigint, bigserial	Int64
real	Float32
double precision	Float64
numeric / decimal	Utf8 (preserves precision)
text, varchar, char	Utf8
bytea	Binary
date	Date32
timestamp	Timestamp(Microsecond)
timestamptz	Timestamp(Microsecond, UTC)
uuid	Utf8
json, jsonb	Utf8
arrays	Utf8 (JSON serialized)

Publishing

The project uses maturin to package the Rust binary as a Python wheel (same approach as ruff, uv, etc). The CI workflow in .github/workflows/release.yml builds wheels for Linux, macOS, and Windows, then publishes to PyPI on tagged releases.

To publish manually:

# Build wheels for current platform
maturin build --release

# Upload to PyPI (needs PYPI_API_TOKEN)
maturin publish

License

MIT