BigQuery

google-cloud-bigquery-backed connector. db_type is bigquery. Tier 1.

Connection config

bigquery

{
  "name": "prod-bigquery",
  "db_type": "bigquery",
  "project": "my-gcp-project",
  "dataset": "analytics",
  "location": "US",
  "credentials_json": "{...service account JSON...}",
  "maximum_bytes_billed": 10737418240
}

Connection fields

Field	Required	Description
name	Yes	Connection name. [a-zA-Z0-9_-], max 64 chars.
db_type	Yes	bigquery.
project	Yes	GCP project ID.
credentials_json	One of	Service account JSON key (must be a JSON object with a type field). Omit to fall back to ADC or OAuth.
dataset	No	Default dataset; sets the query default_dataset.
location	No	BQ region: US, EU, us-east1, etc.
maximum_bytes_billed	No	Safety limit in bytes; a query fails before execution if it would scan more (e.g. 10737418240 = 10 GB).

Auth methods: service account JSON (credentials_json), OAuth (oauth_access_token), service-account impersonation (impersonate_service_account), or Application Default Credentials (adc, the fallback). BigQuery does not use the shared SSL/timeout fields.

Capabilities

Capability	Supported	Notes
Query	Yes	Per-query job stats captured: bytes processed, bytes billed, cache hit, estimated USD cost.
Schema introspection	Yes (full)	Lists datasets and tables via the client API; nested RECORD/STRUCT fields are flattened with dotted names. Detects VIEW / MATERIALIZED_VIEW.
FK discovery	Limited	BigQuery does not enforce FKs at write time.
EXPLAIN	Yes	Query plan with per-stage byte estimates.
Cost estimation	Yes (exact)	Dry-run returns exact bytes that would be processed and an estimated USD cost. estimate_query_cost is highly accurate.
Schema stats	Yes	num_rows and num_bytes per table; time partitioning field/type and clustering fields.

Tier 1.

Dialect notes / gotchas

• Identifiers are quoted with backticks. Table references take the form `project.dataset.table`.
• Each query job has roughly 500ms of overhead; sample-value lookups batch columns into a single UNION ALL query.
• Use UNNEST for array expansion, STRUCT, ARRAY_AGG, DATE_DIFF/DATE_ADD, and EXCEPT/REPLACE in SELECT.
• Set maximum_bytes_billed to cap scan cost; queries that would exceed it fail before running.

Blocked functions

This BigQuery function is blocked inside SELECT (plus all DDL/DML):

• external_query (Cloud SQL federated queries)

The universal load_extension / install_extension block also applies.

Recommended plugin skill

bigquery-sql — UNNEST, STRUCT, ARRAY_AGG, partitioned and wildcard tables, backtick-quoted references, EXCEPT/REPLACE.

Cloud vs local

Cloud-only warehouse. In cloud mode, hostnames are validated against the SSRF allow-list (bigquery.googleapis.com is allowed by default).