PDE Maintaining and Automating Data Workloads Practice Question
You need to estimate the cost of a BigQuery query before running it. Which command or feature should you use?
⚠ Common exam trap
A common trap is confusing the EXPLAIN command (which shows the query plan) with the `--dry_run` flag (which estimates bytes processed and cost).
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the bq command with the --dry_run flag.
The `bq` command with the `--dry_run` flag allows you to estimate the amount of data a BigQuery query will process before actually executing it. This dry run does not read any data or incur charges; it simply returns the estimated bytes to be processed, which you can use to calculate the cost based on BigQuery's pricing model.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Check the BigQuery jobs list for similar queries.
Why it's wrong here
The jobs list shows past costs but not an estimate for a new query.
- ✗
Use the BigQuery cache to estimate if the query is cached.
Why it's wrong here
Caching doesn't provide cost estimation; it avoids charges for rerun queries.
- ✗
Run EXPLAIN on the query to see the query plan.
Why it's wrong here
EXPLAIN shows the execution plan but not the cost estimate.
- ✓
Use the bq command with the --dry_run flag.
Why this is correct
Dry run estimates the bytes processed, allowing cost estimation without running the query.
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