dbt-pybridge 0.1.0

Run dbt Python models locally and materialize results back to Postgres

dbt-pybridge

dbt-pybridge is a dbt adapter that enables Python models in a normal dbt run against Postgres.

It works by:

• compiling .py models through dbt
• executing Python locally (developer laptop or CI runner)
• loading dbt.ref() / dbt.source() data into pandas/polars
• writing the returned dataframe back into Postgres

Status

MVP scope for Python table + incremental + view materializations is implemented.

• Supported: materialized='table'
• Supported: materialized='incremental' (strategies: append, merge, delete+insert)
• Supported: materialized='view' (implemented as a managed backing table + SQL view)
• Supported DAG: sql -> python -> sql
• Supported return types: pandas DataFrame, polars DataFrame, or iterable/generator of dataframes

Install

pip install -e .

Use a supported Python version (3.11/3.12 recommended).

Profile

Set your profile type to pybridge:

my_profile:
  target: dev
  outputs:
    dev:
      type: pybridge
      host: localhost
      user: postgres
      password: postgres
      port: 5432
      dbname: analytics
      schema: public
      threads: 1

Example model

def model(dbt, session):
    df = dbt.ref("stg_orders")
    df["double_amount"] = df["amount"] * 2
    return df

How to create Python models

1. Create models/<name>_python.py.
2. Define exactly one callable entrypoint: def model(dbt, session): ....
3. Set materialization inside the function:
   • dbt.config(materialized="table")
4. Read upstream inputs using standalone ref/source assignments (important for dbt parser):
   • orders = dbt.ref("stg_orders")
   • raw_orders = dbt.source("raw", "orders")
5. Return one of:
   • pandas DataFrame
   • polars DataFrame
   • iterable/generator that yields pandas/polars DataFrames

Parser-safe pattern:

def model(dbt, session):
    dbt.config(materialized="table")
    orders = dbt.ref("stg_orders")
    result = orders.copy()
    result["double_amount"] = result["amount"] * 2
    return result

Chunked mode:

def model(dbt, session):
    for batch in dbt.ref("stg_orders").iter_batches(batch_size=100_000):
        yield transform(batch)

Runtime configs

Set model-level configs via dbt.config(...) in your python model:

• localpy_dataframe_backend: pandas (default) or polars
• localpy_max_rows: hard limit before failure (default 1_000_000)
• localpy_warn_rows: warning threshold (default 200_000)
• localpy_max_bytes: hard estimated table-size limit before failure (default 536870912, 512MB)
• localpy_warn_bytes: warning estimated table-size threshold (default 134217728, 128MB)
• localpy_allow_large_tables: bypass hard row limit (default false)
• localpy_chunked_mode: allow oversized input only when using iter_batches (default false)
• localpy_batch_size: default batch size for iter_batches (default 100_000)
• localpy_column_types: optional explicit type map for created target tables, for example:
  • {"id": "numeric(18,0)", "created_at": "timestamp", "payload": "jsonb"}
• localpy_categorical_types: optional categorical-column enum type map, for example:
  • {"status": "status_enum", "tier": "tier_enum"}

Type inference details

Default inferred target types now include:

• Numeric widths:
  • smallint / integer / bigint / numeric (for wide unsigned integers)
  • real / double precision
• Temporal:
  • date, time, timetz, timestamp, timestamptz, interval
• Structured / special:
  • uuid, bytea, jsonb
• Arrays (homogeneous scalar list/tuple object columns):
  • boolean[], bigint[], double precision[], text[], uuid[], date[], time[], timetz[], timestamp[], timestamptz[], numeric[]
  • mixed or nested list structures fall back to jsonb

Notes:

• Decimal object columns infer numeric(precision,scale) from sampled values.
• Empty or ambiguous object columns fall back to text (or jsonb for ambiguous list structures).
• You can always override with localpy_column_types.

Honest limitations

• Not Snowpark
• Not Spark
• Python runs on local machine / CI runner
• Not intended for huge tables
• Best for small/medium transforms

First milestone command

dbt run -s customer_features

More examples

The examples/mvp_project/ directory has runnable models for each major feature:

• customer_features.py — minimal pandas table model
• orders_polars.py — polars backend (localpy_dataframe_backend='polars')
• daily_revenue_incremental.py — incremental + merge strategy with unique_key
• orders_with_jsonb.py — localpy_column_types overrides for jsonb, text[], and numeric(18,4)

cd examples/mvp_project
dbt run -s orders_polars
dbt run -s daily_revenue_incremental
dbt run -s daily_revenue_incremental                # second run exercises merge
dbt run -s daily_revenue_incremental --full-refresh # rebuild from scratch
dbt run -s orders_with_jsonb