The UNDROP command in Snowflake is a powerful data recovery feature that allows users to restore objects that have been accidentally or intentionally dropped. This command is part of Snowflake's Time Travel capability, which maintains historical data for a specified retention period.
The UNDROP co…The UNDROP command in Snowflake is a powerful data recovery feature that allows users to restore objects that have been accidentally or intentionally dropped. This command is part of Snowflake's Time Travel capability, which maintains historical data for a specified retention period.
The UNDROP command can be used to recover several types of objects including databases, schemas, tables, and tags. When an object is dropped in Snowflake, it is not permanently deleted right away. Instead, it moves to a recoverable state where it remains accessible for restoration during the Time Travel retention period.
The syntax for using UNDROP is straightforward. For example, to restore a dropped table, you would use: UNDROP TABLE table_name. Similarly, you can restore schemas with UNDROP SCHEMA schema_name or databases with UNDROP DATABASE database_name.
There are important considerations when using UNDROP. First, the restoration must occur within the Time Travel retention period, which can range from 0 to 90 days depending on your Snowflake edition and object configuration. Standard edition supports up to 1 day, while Enterprise edition and higher support up to 90 days.
Second, if a new object with the same name has been created after the original was dropped, you must first rename the new object before executing the UNDROP command. This is because Snowflake cannot have two objects with identical names in the same scope.
Third, when you restore a database or schema, all child objects that existed at the time of dropping are also restored, maintaining the hierarchical structure.
The UNDROP feature provides significant protection against accidental data loss and supports business continuity by enabling quick recovery of critical data assets. This capability is essential for maintaining data governance and ensuring that organizations can recover from human errors or unintended deletions efficiently. Understanding UNDROP is crucial for the SnowPro Core Certification as it demonstrates knowledge of Snowflake's data protection mechanisms.
UNDROP Command in Snowflake: Complete Guide for SnowPro Core Certification
What is the UNDROP Command?
The UNDROP command in Snowflake is a powerful data recovery feature that allows you to restore dropped (deleted) objects. This command leverages Snowflake's Time Travel capability to recover databases, schemas, tables, and other objects that have been accidentally or intentionally dropped.
Why is UNDROP Important?
• Data Recovery: Provides a safety net against accidental deletions • Business Continuity: Enables quick restoration of critical data assets • Reduced Downtime: Eliminates the need for lengthy backup restoration processes • Cost Efficiency: Avoids expensive data recovery procedures • Compliance: Helps maintain data governance and audit requirements
How UNDROP Works
When you drop an object in Snowflake, it is not permanently deleted. Instead, it moves to a recoverable state for the duration of the Time Travel retention period (1-90 days depending on your Snowflake edition and settings).
Supported Objects for UNDROP: • Tables • Schemas • Databases
1. Name Conflicts: If an object with the same name already exists, the UNDROP command will fail. You must rename or drop the existing object first.
2. Time Travel Dependency: UNDROP relies on Time Travel retention. Once the retention period expires, the object cannot be recovered using UNDROP.
3. Hierarchical Recovery: To undrop a table, its parent schema must exist. To undrop a schema, its parent database must exist.
4. Transient and Temporary Objects: These have limited Time Travel (0-1 day), affecting UNDROP availability.
5. Multiple Drops: If you dropped an object multiple times (with recreations in between), UNDROP restores the most recently dropped version.
Exam Tips: Answering Questions on UNDROP Command
• Remember the Prerequisites: The parent container (database for schema, schema for table) must exist before you can undrop a child object.
• Time Travel Connection: Understand that UNDROP functionality is tied to Time Travel retention periods. Questions may test whether you know that expired Time Travel data cannot be recovered.
• Name Collision Scenarios: Be prepared for questions about what happens when you try to UNDROP an object but another object with the same name exists. The answer is always that the operation fails.
• Edition Differences: Standard Edition has 1-day Time Travel, while Enterprise Edition and higher can have up to 90 days. This affects how long UNDROP remains viable.
• Object Types: Know that UNDROP works for databases, schemas, and tables. It does NOT work for stages, file formats, pipes, or other objects.
• Fail-safe vs Time Travel: UNDROP uses Time Travel, not Fail-safe. Fail-safe is a 7-day period after Time Travel expires and is only accessible by Snowflake support.
• Privileges Required: The user must have ownership or appropriate privileges on the object to perform UNDROP.
Common Exam Question Patterns:
• Scenario-based questions asking how to recover a dropped table • Questions about what happens when UNDROP conflicts with existing objects • Time Travel retention period impact on UNDROP availability • Distinguishing between objects that can and cannot be undropped