dbt-bigquery-ext

DataEng AI fork of dbt-bigquery (based on 1.12.1), published as a drop-in replacement.

• PyPI: dbt-bigquery-ext
• Import / adapter type: still dbt.adapters.bigquery / type: bigquery in profiles
• Do not install alongside upstream dbt-bigquery (same Python package path)

Install

pip uninstall -y dbt-bigquery
pip install dbt-bigquery-ext

execute_ext

Runs the model's main SQL once per variable set, in parallel, as a BigQuery parameterized query (@name placeholders). The adapter overrides the core statement macro and, when config.execute_ext is set, sends only the main statement through adapter.execute_ext.

execute_ext is allowed only on materializations incremental_ext and script. Any other materialization raises.

Without execute_ext config, behavior matches upstream dbt-bigquery. incremental_ext and script are still available and run their main SQL once.

incremental_ext

Incremental materialization for parameterized fan-out via execute_ext. It does not CREATE OR REPLACE the target and it does not build a shared dataset __dbt_tmp.

Serial, once per run:

1. On --full-refresh, DROP the existing relation. Truncate would keep the old partition and cluster spec and fail when those change.
2. CREATE TABLE IF NOT EXISTS <target> AS SELECT * FROM (<model>) WHERE FALSE so a missing table is created empty, with the current partition and cluster config.
3. When on_schema_change is not ignore, create a dataset temp the same empty way, apply the schema change to the target, then drop the temp.

incremental_strategy is merge (default) or insert_overwrite.

merge (default)

The main statement is one BigQuery script per variable set:

BEGIN
  DECLARE _dbt_merge_partition_dates ARRAY<DATE>;

  CREATE TEMP TABLE _dbt_ext_src AS (
    <model sql, with @parameters>
  );

  SET _dbt_merge_partition_dates = (
    SELECT ARRAY_AGG(dt) FROM (
      SELECT DISTINCT DATE(<partition_field>) AS dt FROM _dbt_ext_src
      WHERE <partition_field> IS NOT NULL
    )
  );

  MERGE INTO <target> ... USING (SELECT * FROM _dbt_ext_src) ...
    ON (...keys...)
   AND DATE(DBT_INTERNAL_DEST.<partition_field>) IN UNNEST(
         IFNULL(_dbt_merge_partition_dates, [DATE '1900-01-02'])
       );
END;

CREATE TEMP TABLE lives in that script's job, so concurrent execute_ext workers do not see each other's temp tables. Each merge writes only its own rows into the shared target. unique_key is optional: with it, matched rows update; without it, the merge is insert-only (append), same as regular incremental + merge.

Partition predicates (always on for time-partitioned merge): both incremental and incremental_ext load distinct DATE(<partition_field>) values from the staging relation into a script variable and filter with IN UNNEST(...) (verified to partition-prune on BigQuery). Regular incremental always builds __dbt_tmp for time-partitioned merge (even when on_schema_change='ignore') so the MERGE script can SET the variable from it. Applies when partition_by.data_type is date / timestamp / datetime — no config flag.

merge_skip_unchanged

On incremental and incremental_ext with incremental_strategy='merge' and a unique_key, skip no-op updates when matched row data is unchanged:

WHEN MATCHED
  AND (
    STRUCT(DBT_INTERNAL_SOURCE.`name`, DBT_INTERNAL_SOURCE.`status`)
    IS DISTINCT FROM
    STRUCT(DBT_INTERNAL_DEST.`name`, DBT_INTERNAL_DEST.`status`)
  )
THEN UPDATE SET ...

Uses BigQuery STRUCT(...) IS DISTINCT FROM STRUCT(...) (null-safe; no JSON/hash). Compare columns must be groupable (not GEOGRAPHY / JSON, etc.).

{{ config(
    materialized="incremental",  -- or incremental_ext
    incremental_strategy="merge",
    unique_key="id",
    merge_skip_unchanged=true,
    -- XOR: at most one of:
    -- stable_columns=["name", "status"],           -- compare only these
    -- unstable_columns=["__ingestion_time"],       -- compare all except these
    -- neither → compare all target columns (minus unique_key)
) }}

• Requires unique_key; rejected on insert_overwrite / microbatch
• unique_key columns are omitted from the compare set automatically
• Independent of merge_update_columns / merge_exclude_columns (those control the SET list)
• First run / full refresh: no matched rows (or CTAS) → no-op for this predicate
• Schema append: compare uses current dest_columns after schema sync

insert_overwrite

Same staging temp as merge, then DELETE + MERGE in a transaction:

BEGIN
  DECLARE _dbt_merge_partition_dates ARRAY<DATE>;

  CREATE TEMP TABLE _dbt_ext_src AS (
    <model sql, with @dt>
  );

  BEGIN TRANSACTION;

  DELETE FROM <target>
  WHERE DATETIME_TRUNC(CAST(dt AS DATETIME), DAY) = DATETIME_TRUNC(CAST(@dt AS DATETIME), DAY);  -- shape depends on data_type/granularity

  MERGE INTO <target> ...
  USING (
    SELECT * FROM _dbt_ext_src
    WHERE DATETIME_TRUNC(CAST(dt AS DATETIME), DAY) = DATETIME_TRUNC(CAST(@dt AS DATETIME), DAY)
  ) ...
  ;

  COMMIT TRANSACTION;
END;

insert_overwrite_mode chooses consistency vs parallel throughput:

Mode	Behavior
consistency (default)	BEGIN TRANSACTION around DELETE+MERGE; worker_pool_size forced to 1 (BigQuery rejects concurrent transactions on one table)
scalability	No transaction; parallel execute_ext shards allowed. If MERGE fails after DELETE, that partition may be left empty

(Exact predicate uses {DATA_TYPE}_TRUNC(CAST(col AS …), GRAN) when needed — e.g. TIMESTAMP_TRUNC(..., HOUR) — or CAST(col AS DATE) = CAST(@param AS DATE) for date + day. Both sides are cast so column storage type need not match partition_by.data_type exactly.)

This keeps temp creation identical to merge and applies the partition guard on the MERGE source (same place merge already reads SELECT * FROM _dbt_ext_src).

Requirements:

• Time partitioning only: partition_by.data_type in date / timestamp / datetime
• Granularity hour / day / month / year (hour requires timestamp/datetime)
• execute_ext required; each variable set has exactly one parameter (name may differ from partition_by.field, e.g. @dt vs column __taken_at_utc)
• Parameter type DATE / STRING / TIMESTAMP / DATETIME; values coerce to the partition type. For hour, pass a timestamp/datetime (not date-only)
• Variable sets are deduped by partition bucket (first wins) so duplicate days/hours do not race
• Optional insert_overwrite_mode: consistency | scalability
• unique_key is not allowed
• copy_partitions is not supported (see below)

copy_partitions (upstream dbt-bigquery): when true, regular incremental + insert_overwrite can replace partitions by copying whole partition shards (table$YYYYMMDD) via the BigQuery Jobs API instead of row SQL. incremental_ext does not implement that path — it always runs DELETE of the matching bucket then insert-only MERGE. Passing copy_partitions: true raises.

{{ config(
    materialized="incremental_ext",
    incremental_strategy="insert_overwrite",
    insert_overwrite_mode="scalability",  -- or "consistency" (default)
    partition_by={"field": "__taken_at_utc", "data_type": "datetime", "granularity": "day"},
    execute_ext={
        "variable_set_sql": "SELECT dt FROM UNNEST([DATE '2026-09-01', DATE '2026-09-03']) AS dt",
        "worker_pool_size": 0,  -- auto = dbt threads / --threads
    },
) }}

select
  @dt as dt,
  cast(@dt as timestamp) as __taken_at_utc

DELETE/MERGE compare CAST(<partition_by.field> AS <data_type>) to CAST(@<sole_param> AS <data_type>) (with _TRUNC when needed), so the parameter name and physical column type need not match partition_by exactly.

Relation markers (ref / source)

When a model sets mark_relations=true, or uses materialization incremental_ext / script, overridden ref / source return a Relation whose render() wraps the FQN via relation_marker:

/* <ref:dim_products> */`proj`.`ds`.`dim_products`/* <ref:dim_products> */
/* <source:raw:jobs> */`proj`.`ds`.`jobs`/* <source:raw:jobs> */

Path metadata (.database / .schema / .identifier) stays the original. Ephemeral refs are unmarked. Materialization-time substitute of these markers is not implemented yet.

Variable sets

Pass exactly one of:

1. variable_set_values — explicit list of dicts, optional variable_set_types
2. variable_set_relation — a relation (ref / source / Relation). dbt runs SELECT *, each row becomes one variable set, and parameter types come from the BigQuery schema. Do not pass variable_set_types with a relation.
3. variable_set_sql — a SQL string that returns one row per variable set (column names = parameter names). Types come from the result schema. Do not pass variable_set_types with SQL. Prefer a simple query (e.g. UNNEST of a few dates). The SQL may run more than once per dbt invocation (serial DDL + resolve); for expensive logic, put results in a table and use variable_set_relation instead.

-- explicit
{{ config(
    materialized="incremental_ext",
    unique_key="order_id",
    execute_ext={
        "variable_set_values": [
            {"store_id": 1, "region": "us"},
            {"store_id": 2, "region": "eu"},
        ],
        "variable_set_types": {"store_id": "INT64", "region": "STRING"},
        "worker_pool_size": 0,
    },
) }}

-- from a control table (columns = parameter names)
{{ config(
    materialized="incremental_ext",
    execute_ext={
        "variable_set_relation": ref("store_shards"),
        "worker_pool_size": 0,
    },
) }}

-- from ad-hoc SQL (e.g. always reprocess yesterday + today)
{{ config(
    materialized="incremental_ext",
    incremental_strategy="insert_overwrite",
    partition_by={"field": "dt", "data_type": "date"},
    execute_ext={
        "variable_set_sql": "SELECT dt FROM UNNEST([CURRENT_DATE() - 1, CURRENT_DATE()]) AS dt",
        "worker_pool_size": 0,
    },
) }}

Passing more than one of variable_set_values / variable_set_relation / variable_set_sql raises. Rows must not contain NULL in parameter columns (BigQuery query parameters cannot be NULL).

Model config

-- models/orders_by_store.sql
{{ config(
    materialized="incremental_ext",
    unique_key="order_id",
    execute_ext={
        "variable_set_values": [
            {"store_id": 1, "region": "us"},
            {"store_id": 2, "region": "eu"},
        ],
        "variable_set_types": {"store_id": "INT64", "region": "STRING"},
        "worker_pool_size": 0,
    },
) }}

select *
from {{ source("raw", "orders") }}
where store_id = @store_id
  and region = @region

Each dict in variable_set_values is one script. The serial DDL (empty create, schema probe) binds only the first set so @store_id / @region are valid there too. Merges must be idempotent: a failure does not roll back sets that already succeeded.

The same execute_ext block works in dbt_project.yml or a schema.yml config: entry.

script

script runs compiled_code as the main statement and returns no relation. Use it for a hand-written BigQuery script. With execute_ext, that script is fanned out the same way. Give each run its own CREATE TEMP TABLE if it stages rows before writing.

{{ config(
    materialized="script",
    execute_ext={
        "variable_set_values": [{"store_id": 1}, {"store_id": 2}],
        "variable_set_types": {"store_id": "INT64"},
    },
) }}

create temp table _batch as (
  select * from {{ source("raw", "orders") }} where store_id = @store_id
);
merge into {{ this }} as t
using _batch as s
on t.order_id = s.order_id
when matched then update set t.amount = s.amount
when not matched then insert (order_id, amount) values (s.order_id, s.amount)

Direct call from a macro

{% macro refresh_stores(store_ids) %}
  {% set values = [] %}
  {% for store_id in store_ids %}
    {% do values.append({"store_id": store_id}) %}
  {% endfor %}

  {% set response, table = adapter.execute_ext(
      "delete from " ~ target.database ~ "." ~ target.schema ~ ".orders where store_id = @store_id",
      variable_set_values=values,
      variable_set_types={"store_id": "INT64"},
      worker_pool_size=-1,
  ) %}
{% endmacro %}

Omit variable_set_values (or pass none) and execute_ext falls back to a normal execute.

Cloud SQL gateway (checkpoints)

Optional SQLMesh-style state backend on the BigQuery profile. Uses the Cloud SQL Python Connector with IAM DB auth (no password). Intended to replace the dbt-webhook → Cloud Function → Postgres path for delta checkpoints (public.dbt_model_log).

Profile

my_target:
  type: bigquery
  method: oauth  # or service-account / impersonate_service_account
  project: my-gcp-project
  dataset: analytics
  gateway:
    cloudsql:
      instance_connection_name: "my-gcp-project:us-central1:metadata"
      database: metadata
      ip_type: private          # private | public | psc
      schema_name: public
      # user: "dbt-runner@my-gcp-project.iam"  # optional; derived from SA / impersonation
      init_on_connect: true     # ensure schema on first BQ connection
      auto_migrate: true        # reserved; today only CREATE IF NOT EXISTS

IAM DB user for a service account is the SA email with .gserviceaccount.com stripped (name@project.iam). The runner needs roles/cloudsql.client + Cloud SQL Instance User on that instance.

Startup

On the first BigQuery connection (when init_on_connect: true), the adapter connects to Cloud SQL and creates missing tables (see gateway/schema.py):

1. dbt_model_log (+ index)
2. change_tracking_registry
3. change_tracking_log (+ overlap / GIN indexes)

Force early init from dbt_project.yml:

on-run-start:
  - "{{ adapter.gateway_ensure() }}"

Adapter / macros

Call	Role
adapter.gateway_ensure()	Connect + ensure tables
adapter.gateway_get_checkpoint(db, schema, table)	Latest successful row (for pre-hooks)
adapter.gateway_set_checkpoint(...)	Insert row (replaces analytics.set_checkpoint UDF)
adapter.gateway_change_metadata_pooler(relations, …)	Pool CHANGES → registry/log + gateway.pooler.* checkpoints
adapter.gateway_get_affected_partitions(db, schema, table, start, end)	Dirty partition ids (None = all, [] = none)

Jinja wrappers: gateway_ensure, gateway_get_checkpoint, gateway_set_checkpoint, gateway_pool_change_metadata, gateway_get_affected_partitions.

Change-metadata pooler

Production path: deploy the Cloud Run service under services/change_metadata_pooler/ (register tables + Cloud Scheduler). Point the adapter at it:

gateway:
  cloudsql: { ... }   # still used for checkpoints / local fallback
  pooler_url: https://change-metadata-pooler-xxxxx.run.app

When pooler_url is set, gateway_pool_change_metadata and gateway_get_affected_partitions (with ensure_fresh=true by default) call the service over HTTP (OIDC). Prefer that over in-process pooling in shared envs.

Dev/POC only — dbt graph pool: mark models/sources and call from on-run-start (not recommended for production):

# models/schema.yml or sources.yml
models:
  - name: orders
    config:
      enable_changetracking: true

sources:
  - name: raw
    tables:
      - name: events
        meta:
          enable_changetracking: true

on-run-start:
  # POC: in-process graph pool. Prefer Cloud Run + pooler_url above.
  - "{{ gateway_pool_change_metadata(worker_pool_size=0) }}"

For each distinct FQN the pooler:

1. Reads partition type/field/grain from BigQuery table metadata (not dbt partition_by)
2. Enables change history if needed
3. On first see: logs status=initial with partition_ids NULL (entire table) and sets a gateway.pooler. checkpoint
4. Later: runs a single CHANGES aggregation → string partition ids + COUNT(*) / COUNTIF per _CHANGE_TYPE, writes an append-only log row, advances the pooler checkpoint in the same Postgres transaction

Partition id formats (UTC strings):

Grain	Example
hour	2026-09-20 14:00:00
day / week / month	2026-09-20 / week-start / month-start

partition_ids on the log:

Value	Meaning
NULL	Entire table / all partitions
{}	No changes in the window
{id,…}	Those partitions only

Query dirty partitions for a time range (overlap on log delta_*):

{% set parts = gateway_get_affected_partitions(ref('orders'), start_ts, end_ts) %}
{# none → all table; [] → no changes; list → ids #}

Example commit (post-hook), after you switch off the remote UDF:

{% do adapter.gateway_set_checkpoint(
    invocation_id,
    this.database,
    this.schema,
    this.identifier,
    run_started_at | string,
    node_started_at | string,
    modules.datetime.datetime.utcnow() | string,
    delta_start_time | string,
    delta_end_time | string,
) %}

worker_pool_size

Value	Workers
0 (default)	auto = dbt threads / --threads (capped at job count; fallback 16)
-1	one worker per variable set
> 0	that many workers (maximum 1024)

Types

Scalar types only (STRING, INT64, FLOAT64, BOOL, DATE, TIMESTAMP, and the other BigQuery scalars). ARRAY and STRUCT are reserved and raise.

• Pass variable_set_types to force types.
• If omitted, types are inferred from the Python/Jinja values.
• null is rejected. BigQuery does not allow NULL query parameters, and inference cannot recover a type from null. Pass an explicit type only when the value itself is non-null.

Failure and logs

Success means every variable set finished. Any failure raises after the pool has drained. Sets that already completed are left in place.

Progress (starting / completed / failed / retried) is debug-only. Retries use the same profile settings as a normal BigQuery job.

dbt run --select orders_by_store --debug

Versioning

Two version strings, because dbt and PyPI do not accept the same syntax.

String	Where	Example	Why
version	dbt.adapters.bigquery.__version__ (what dbt debug parses)	1.12.1	dbt's semver rejects 1.12.1.post12 and aborts
pypi_version	PyPI / wheel name	1.12.1.post12	DataEng release N on top of upstream 1.12.1

pypi_version scheme:

<upstream dbt-bigquery version>.post<N>

PyPI version	Meaning
1.12.1.post1	First DataEng release on upstream 1.12.1
1.12.1.post2	Second DataEng-only release, same upstream base
1.12.1.post3	Third DataEng-only release, same upstream base
1.12.1.post4	Fourth DataEng-only release, same upstream base
1.12.1.post5	Fifth DataEng-only release, same upstream base
1.12.1.post6	Sixth DataEng-only release, same upstream base
1.12.1.post7	Seventh DataEng-only release, same upstream base
1.12.1.post8	Eighth DataEng-only release, same upstream base
1.12.1.post9	Ninth DataEng-only release, same upstream base
1.12.1.post10	Tenth DataEng-only release, same upstream base
1.12.1.post11	Eleventh DataEng-only release, same upstream base
1.12.1.post12	Twelfth DataEng-only release, same upstream base
1.13.0.post1	Rebased onto upstream 1.13.0

On a rebase, set version to the new upstream number (1.13.0) and pypi_version to 1.13.0.post1. Do not put .postN into version. Local versions (1.12.1+dataeng.1) cannot be uploaded to PyPI.

Upstream

Apache-licensed code from dbt Labs; see LICENSE. Upstream project: https://github.com/dbt-labs/dbt-adapters/tree/main/dbt-bigquery

Getting started

For BigQuery profile setup, see the dbt BigQuery docs.