Design innovative, scalable, and highly available cloud database solutions →hardMultiple ChoiceObjective-mapped
PCDE Practice Question: Design innovative, scalable, and highly available cloud database solutions
An organization uses Cloud Spanner and needs to add a new column to an existing table without downtime. The table has billions of rows and is heavily used. What is the recommended approach to add the column?
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 ALTER TABLE ADD COLUMN statement
Cloud Spanner schema changes are online and non-blocking, so you can simply use ALTER TABLE to add the column; it will not cause downtime.
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 ALTER TABLE ADD COLUMN statement
Why this is correct
Spanner allows non-blocking schema updates; ALTER TABLE is safe and does not require downtime.
- ✗
Create a new table with the column, then copy data and rename
Why it's wrong here
Unnecessary and could cause downtime; Spanner supports online schema changes.
- ✗
Add the column using gcloud command and set a downtime window
Why it's wrong here
No downtime window needed; schema changes are online.
- ✗
Backup the database, add column, then restore
Why it's wrong here
Unnecessarily disruptive and may cause data loss.
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