PDE Maintaining and Automating Data Workloads Practice Question
An organization uses BigQuery on-demand pricing. To control costs, they want to estimate the bytes processed by a query before running it. Which command or method should they use?
⚠ Common exam trap
PDE often tests the difference between pre-execution estimation and post-hoc cost inspection, so the trap is choosing INFORMATION_SCHEMA.JOBS_BY_PROJECT (which shows past bytes billed) instead of --dry_run for estimating before running.
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 query --dry_run command
The bq query --dry_run flag validates a query and returns the estimated bytes that would be processed without actually executing it or incurring charges. This is the standard method to estimate on-demand BigQuery costs before running a query, since on-demand pricing is based on bytes processed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use the bq query --dry_run command
Why this is correct
The `bq query --dry_run` flag validates a query and returns the bytes it would process without executing it, so no on-demand charges are incurred. This directly satisfies the requirement to estimate bytes processed beforehand, letting the organisation predict cost before committing to the query.
- ✗
Use bq ls to list table sizes
Why it's wrong here
Listing tables with bq ls returns dataset metadata such as table names and creation dates, not the bytes a specific query will scan. It is tempting because it inspects BigQuery objects, but estimating on-demand cost requires a dry run, which reports totalBytesProcessed without executing the query.
- ✗
Use BigQuery reservations to get cost estimate
Why it's wrong here
Reservations allocate dedicated slot capacity for predictable workloads, not per-query byte estimates under on-demand pricing. It tempts as a cost-control tool, but reservations change billing to capacity-based commitments; a dry run is what returns bytes processed before execution.
- ✗
Use INFORMATION_SCHEMA.JOBS_BY_PROJECT to view past costs
Why it's wrong here
INFORMATION_SCHEMA.JOBS_BY_PROJECT reports bytes and costs of queries already executed, so it cannot estimate a query before running it. It tempts for cost visibility, but that is retrospective analysis; a dry run returns the bytes the query would process beforehand.
About these practice questions
One of 747 original PDE practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
This PDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PDE exam.