One frequently asked question in the context of using dbt tool is:
Can I connect my dbt project to two databases?
(see the answered question on the dbt website).
tldr; dbt stands for transformation as in T within ELT pipelines, it doesn't move data from source to a warehouse.
The creators of the dbt tool have added however support for handling such scenarios via
dbt-presto plugin.
This repository represents a fork of the dbt-presto with slight adaptations to make it work with Trino SQL compute engine.
This dbt plugin has been tested against dbt version 0.20.1 and trino version 360.
This dbt adapter can be installed via pip:
$ pip install dbt-trino
A dbt profile can be configured to run against Trino using the following configuration:
| Option | Description | Required? | Example |
|---|---|---|---|
| method | The Trino authentication method to use | Optional (default is none) |
none or kerberos |
| user | Username for authentication | Required | commander |
| password | Password for authentication | Optional (required if method is ldap or kerberos) |
none or abc123 |
| database | Specify the database to build models into | Required | analytics |
| schema | Specify the schema to build models into. Note: it is not recommended to use upper or mixed case schema names | Required | public |
| host | The hostname to connect to | Required | 127.0.0.1 |
| port | The port to connect to the host on | Required | 8080 |
| threads | How many threads dbt should use | Optional (default is 1) |
8 |
Example profiles.yml entry:
my-trino-db:
target: dev
outputs:
dev:
type: trino
user: commander
host: 127.0.0.1
port: 8080
database: analytics
schema: public
threads: 8
Due to the nature of Trino, not all core dbt functionality is supported.
The following features of dbt are not implemented on Trino:
- Archival
- Incremental models
Also, note that upper or mixed case schema names will cause catalog queries to fail. Please only use lower case schema names with this adapter.
dbt fundamentally works by dropping and creating tables and views in databases. As such, the following Trino configs must be set for dbt to work properly on Trino:
hive.metastore-cache-ttl=0s
hive.metastore-refresh-interval = 5s
hive.allow-drop-table=true
hive.allow-rename-table=true
Build dbt container locally:
./docker/dbt/build.sh
Run a Trino server locally:
./docker/init.bash
If you see errors while about "inconsistent state" while bringing up Trino,
you may need to drop and re-create the public schema in the hive metastore:
# Example error
Initialization script hive-schema-2.3.0.postgres.sql
Error: ERROR: relation "BUCKETING_COLS" already exists (state=42P07,code=0)
org.apache.hadoop.hive.metastore.HiveMetaException: Schema initialization FAILED! Metastore state would be inconsistent !!
Underlying cause: java.io.IOException : Schema script failed, errorcode 2
Use --verbose for detailed stacktrace.
*** schemaTool failed ***
Solution: Drop (or rename) the public schema to allow the init script to recreate the metastore from scratch. Only run this against a test Trino deployment. Do not run this in production!
-- run this against the hive metastore (port forwarded to 10005 by default)
-- DO NOT RUN THIS IN PRODUCTION!
drop schema public cascade;
create schema public;You probably should be slightly less reckless than this.
Run tests against Trino:
./docker/run_tests.bash
Run the locally-built docker image (from docker/dbt/build.sh):
export DBT_PROJECT_DIR=$HOME/... # wherever the dbt project you want to run is
docker run -it --mount "type=bind,source=$HOME/.dbt/,target=/home/dbt_user/.dbt" --mount="type=bind,source=$DBT_PROJECT_DIR,target=/usr/app" --network dbt-net dbt-trino /bin/bash
Install dbt-adapter-tests library to be able to run the dbt tests:
pip install pytest-dbt-adapter
Run from the base directory of the project the command:
pytest test/integration/trino.dbtspec
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