PDE Maintaining and Automating Data Workloads Practice Question
You are designing a data pipeline that ingests streaming data from Pub/Sub, processes it with Dataflow, and writes to BigQuery. You need to ensure that schema changes in the incoming data (new fields) are handled without pipeline failure. Which THREE steps should you take? (Choose THREE.)
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
✓
Set the BigQuery table schema to allow automatic addition of new fields by using 'ignore_unknown_values'.
To handle schema drift, BigQuery allows schema relaxation (adding nullable columns) via DDL. Dataflow can update the destination table schema using BigQuery APIs (e.g., set the schema to include unknown fields). Alternatively, using BigQuery's automatic schema detection with 'ignore_unknown_values' can allow new fields to be added automatically. Setting all fields to NULLABLE in advance is not practical. Setting the table to require all fields causes failures on unknown fields.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Set the BigQuery table schema to allow automatic addition of new fields by using 'ignore_unknown_values'.
Why this is correct
This option tells BigQuery to ignore unknown fields and allows schema auto-detection.
- ✗
Configure the BigQuery table to require all fields, causing the pipeline to fail on unknown fields.
Why it's wrong here
This would cause failures, not handle schema drift.
- ✓
Use ALTER TABLE ADD COLUMN DDL statements to add nullable columns for new fields.
Why this is correct
You can proactively or reactively add nullable columns to handle new fields.
- ✓
Configure the Dataflow pipeline to update the BigQuery table schema when new fields are detected.
Why this is correct
Dataflow can programmatically add new columns to the BigQuery table.
- ✗
Set all columns in the BigQuery table as NULLABLE from the start.
Why it's wrong here
This does not handle new fields that are not already in the schema.
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