Bigquery Observability

BigQuery Observability

Attribution

MUST READ: Before executing any gcloud, REST API, or MCP command, you MUST read Usage Attribution. For commands executed directly in the terminal (never in generated scripts, Terraform, or user code), prefix gcloud with CLOUDSDK_METRICS_REQUEST_ATTRIBUTION="agent-skills/1.0 (skill:bigquery-observability)" and append agent-skills/1.0 (skill:bigquery-observability) to User-Agent headers.

Tool Selection

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Prerequisites & Environment Setup

Before retrieving telemetry or running observability queries, ensure the Google Cloud environment and project are configured:

1. Google Cloud SDK: Ensure the Google Cloud SDK is installed and configured.

2. Project Selection: Set the active Google Cloud project:

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   gcloud config set project {project_id}

3. API Enablement: Ensure the BigQuery and Cloud Monitoring APIs are enabled:

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   gcloud services enable bigquery.googleapis.com monitoring.googleapis.com

4. Authentication: Authenticate the environment:

   • CLI queries and bq commands: gcloud auth login

   • SDKs and automated client tools: gcloud auth application-default login

   • Service accounts: Set GOOGLE_APPLICATION_CREDENTIALS="/path/to/key.json"

5. Billing & IAM Roles:

   • Verify an active Google Cloud Billing account is attached to {project_id}.

   • Ensure appropriate IAM roles:

     • roles/bigquery.jobUser: Running telemetry queries.

     • roles/bigquery.resourceViewer or roles/bigquery.admin: Organization-level jobs and reservation telemetry.

     • roles/monitoring.viewer: Cloud Monitoring metrics.

6. Companion Skills Installation: This skill is part of a 3-pillar operations suite (bigquery-observability, bigquery-optimization, bigquery-troubleshooting). If any companion skill is not yet installed in your environment, install the full suite:

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   npx skills add google/skills --skill bigquery-observability --skill bigquery-optimization --skill bigquery-troubleshooting

Workflow

1. Single-Job Point-Lookup (Zero-SQL Overhead): For single-job slowness or inspection, always prioritize the REST API or CLI (bq show -j) first. It provides zero-SQL overhead and fast point-lookups for internal stage bottlenecks (performanceInsights, queryPlan, shuffle spill).

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   bq show --location={location} -j {project_id}:{job_id}

2. Diagnostic Transition Logic: If no job-level issues are found (e.g. no clear internal bottlenecks), the investigation should transition to system-level INFORMATION_SCHEMA queries (such as JOBS_TIMELINE or RESERVATIONS_TIMELINE) to check for broader issues like slot contention, queueing delay, or noisy neighbors.

Best Practices for Writing INFORMATION_SCHEMA Queries

Every query against a BigQuery INFORMATION_SCHEMA view must be qualified with either a region qualifier or a dataset qualifier, optionally prefixed by a project qualifier.

Qualification Syntax & Scope Matching

1. Region-Qualified Syntax:

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   `{project_id}`.`region-{region}`.INFORMATION_SCHEMA.{view}

   Example: `my-project`.`region-us`.INFORMATION_SCHEMA.JOBS

   Applies to: Regional telemetry views (JOBS*, JOBS_TIMELINE*, RESERVATIONS*, CAPACITY_COMMITMENTS*, TABLE_STORAGE*, STREAMING_TIMELINE*). The client query execution location MUST match the region-{region} qualifier (or BigQuery throws: Not found: Table {project_id}:region-{region}.INFORMATION_SCHEMA.{view} was not found in location {location}).

2. Dataset-Qualified Syntax:

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   `{project_id}`.`{dataset_id}`.INFORMATION_SCHEMA.{view}

   Example: `my-project`.`analytics`.INFORMATION_SCHEMA.TABLES

   Applies to: Dataset-scoped views (PARTITIONS, SEARCH_INDEXES*, ROW_ACCESS_POLICIES). Never use region- with dataset views.

3. Dual-Scoped Views: Views like TABLES, COLUMNS, COLUMN_FIELD_PATHS, VIEWS, ROUTINES, and VECTOR_INDEXES can be qualified with either {dataset_id} or region-{region} depending on whether dataset or region-wide analysis is required.

4. Project Qualifier ({project_id}): Optional. If omitted, queries default to the project in which the query is executing. Specifying a project qualifier on organization-level views (e.g. JOBS_BY_ORGANIZATION) has no impact on results.

Principle of Least Privilege & Scope Selection

When constructing INFORMATION_SCHEMA queries, always select the scope and view variant with the least IAM permission requirement that satisfies the analytical need:

1. User-Level over Project-Level (_BY_USER): When diagnosing queries or sessions executed by the current user, use _BY_USER (e.g. JOBS_BY_USER, SESSIONS_BY_USER). This requires only bigquery.jobs.list (granted via roles/bigquery.user or roles/bigquery.jobUser), avoiding the need for bigquery.jobs.listAll or roles/bigquery.admin.

2. Dataset-Level over Region/Project-Level: When querying table metadata, columns, or views for a specific dataset, qualify with {dataset_id} rather than region-{region} when project-level metadata access is restricted. Dataset-scoped queries require permissions only on that target dataset.

3. Project-Level over Org/Folder-Level (_BY_PROJECT): Always start with project-scoped views before escalating to _BY_FOLDER or _BY_ORGANIZATION. Folder and organization queries require broad folder/org IAM permissions (bigquery.jobs.listAll or bigquery.tables.list at the Org/Folder node).

4. Metadata Roles over Data Roles: For table and storage introspection, prefer roles/bigquery.metadataViewer (which provides bigquery.tables.get and bigquery.tables.list) over roles/bigquery.dataViewer or roles/bigquery.dataOwner when data read access (bigquery.tables.getData) is not needed. (Note: INFORMATION_SCHEMA.PARTITIONS uniquely requires bigquery.tables.getData).

Execution Guardrails & Query Invariants

• Mandatory Partition & Time Filtering: Always filter on creation_time (e.g., creation_time >= TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 3 DAY)) or usage_date to avoid full metadata table scans.

• Script Wrapper Exclusion: Add AND (statement_type != 'SCRIPT' OR statement_type IS NULL) when aggregating compute spend to avoid double-counting parent scripts and child jobs.

• Column Pruning: Never use SELECT * against INFORMATION_SCHEMA; only project required columns.

• Dry Run & Cost Estimation: Use a dry run (bq query --dry_run --use_legacy_sql=false "{query}" or API dryRun=true) before executing complex queries, multi-view joins, or large scans to validate syntax and estimate totalBytesProcessed at zero cost.

• Empty Regional Scope (0 Rows): If the execution location matches the qualifier, but the project has no datasets or jobs in that region, the query succeeds and returns 0 rows. Never assume 0 rows means 0 usage—always verify the target dataset locations.

• Non-Hierarchical Region Scope: Region qualifiers are not hierarchical. Multi-regions do not encompass single regions (e.g. region-us returns only multi-region US metadata and does not include single regions like region-us-central1).

• No Multi-Region Aggregation in SQL: Region qualifiers cannot be joined cross-region in a single query (e.g. region-us cannot join region-eu).

• Uncached Execution & Minimum Scan Size: INFORMATION_SCHEMA query results are never cached. On-demand queries incur a minimum of 10 MB of data processing charges per execution.

Domain References & SQL Queries

Telemetry Query Guides

• On-Demand Compute: Billed Bytes (references/compute_ondemand_billable.md): Authoritative Golden CTE (bytes_billed_cte), timezone-aligned billing date extraction (PST8PDT), BQML CREATE_MODEL 50x multiplier rules, script wrapper deduplication, and row-level security (RLS) masking checks.

• Capacity Compute: Billable Slots & Commitments (references/compute_capacity_billable.md): Query templates for auditing billable capacity hours across 1-Year/3-Year commitments, uncovered baseline PAYG slots, and dynamic autoscaling hours.

• Storage Footprints & Usage (Bytes Stored) (references/storage_footprints.md): Storage snapshot queries, compression ratio calculations, Time Travel / Fail-Safe churn, daily average GiB time-integrals, billing model evaluation, and search index coverage.

Performance & Troubleshooting Guides

• Job Performance Queries (references/job_performance_queries.md): Queries for evaluating individual and aggregate job performance, stage bottleneck flags, comparable jobs via normalized literals (query_info.query_hashes.normalized_literals), BI Engine acceleration, metadata cache (cmeta) acceleration, search index usage, materialized view rewrite usage, and execution variance outliers.

• Resource Contention Queries (references/resource_contention_queries.md): Queries for diagnosing slot contention, queue latency, per-minute concurrency/queue timelines, and 1-second reservation slot saturation.

• Capacity & Configuration Queries (references/capacity_and_configuration_queries.md): Queries for evaluating second-by-second baseline/max capacity ceilings, autoscaling saturation timelines, and auditing configuration changes (RESERVATION_CHANGES_BY_PROJECT, ASSIGNMENT_CHANGES_BY_PROJECT).

Schema Dictionaries (Column Definitions & Units)

• Compute & Capacity Schema Dictionary (references/schema_compute.md): Complete column dictionary, physical units, and least-privilege IAM roles for all compute, job, session, reservation, capacity commitment, and assignment views (JOBS*, JOBS_TIMELINE*, SESSIONS_BY_USER, SESSIONS_BY_PROJECT, RESERVATIONS*, RESERVATION_CHANGES*, RESERVATIONS_TIMELINE*, CAPACITY_COMMITMENTS*, CAPACITY_COMMITMENT_CHANGES_BY_PROJECT, ASSIGNMENTS*, ASSIGNMENT_CHANGES_BY_PROJECT).

• Storage & Data Catalog Schema Dictionary (references/schema_storage.md): Complete column dictionary, physical units, and least-privilege IAM roles for all table storage, partition, column, snapshot, dataset, constraint, and replication views (TABLE_STORAGE*, TABLE_STORAGE_USAGE_TIMELINE*, TABLES*, TABLE_OPTIONS, COLUMNS, COLUMN_FIELD_PATHS, PARTITIONS, VIEWS, MATERIALIZED_VIEWS, TABLE_SNAPSHOTS*, TABLE_CONSTRAINTS, KEY_COLUMN_USAGE, SCHEMATA*, SCHEMATA_OPTIONS, SCHEMATA_REPLICAS*, SCHEMATA_LINKS, SHARED_DATASET_USAGE).

• Platform, Governance & Ingestion Schema Dictionary (references/schema_others.md): Complete column dictionary, physical units, and least-privilege IAM roles for all remaining views including Access Control (OBJECT_PRIVILEGES, ROW_ACCESS_POLICIES, ROW_ACCESS_POLICY_OPTIONS), Streaming Ingestion (STREAMING_TIMELINE_BY_PROJECT*, WRITE_API_TIMELINE_BY_PROJECT*), Configuration Options (PROJECT_OPTIONS*, EFFECTIVE_PROJECT_OPTIONS, ORGANIZATION_OPTIONS*, ORGANIZATION_OPTIONS_CHANGES), Insights & Recommendations (RECOMMENDATIONS*, INSIGHTS), and Indexes/BI Engine/Routines (SEARCH_INDEXES*, SEARCH_INDEX_COLUMNS, SEARCH_INDEX_OPTIONS, VECTOR_INDEXES*, VECTOR_INDEX_COLUMNS, VECTOR_INDEX_OPTIONS, BI_CAPACITIES, BI_CAPACITY_CHANGES, ROUTINES*, ROUTINE_OPTIONS, PARAMETERS).