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CTE Cost Breakdown

Analyze cost per CTE to identify expensive query parts.

Breakdown Display​

Total Cost: $0.045 (9 GB processed)

CTE Breakdown:
┌─────────────────┬──────────┬───────────┬────────┐
│ CTE Name        │ Cost     │ Data      │ % Cost │
├─────────────────┼──────────┼───────────┼────────┤
│ raw_data        │ $0.025   │ 5 GB      │ 55.5%  │
│ user_summary    │ $0.015   │ 3 GB      │ 33.3%  │
│ active_users    │ $0.005   │ 1 GB      │ 11.2%  │
└─────────────────┴──────────┴───────────┴────────┘

Optimization Priority​

% of CostPriority
50%+High - optimize first
20-50%Medium - review
Under 20%Low - skip unless easy

Common Patterns​

Expensive Initial CTE​

Problem: Full table scan in first CTE, filter applied later Solution: Move WHERE filter into the CTE

Data Explosion​

Problem: UNNEST creates 50x more rows than input Solution: Filter before UNNEST

Redundant CTEs​

Problem: CTE just passes through data unchanged Solution: Merge into next CTE

Too Many Columns​

Problem: SELECT * when only 2 columns needed Solution: Select only needed columns

Filter Propagation​

Querylab.io replicates BigQuery's optimization to show realistic estimates.

Works: Simple comparisons, equality, IN, AND combinations

Doesn't work: Aggregation filters, window functions, OR combinations