One of its highly valuable features is the “SNAPSHOT” capability. In this article, we will dive deep into Hive’s “SNAPSHOT” feature, its usage, appropriate scenarios for utilization, available conversions, and even a sample Data Definition Language (DDL) script and insert for practical illustration.
What is Hive “SNAPSHOT”?
Hive’s “SNAPSHOT” feature refers to the ability to take a static view of data at a particular point in time, which can significantly aid in various types of analysis, debugging, and reporting. By creating a snapshot, you’re effectively saving a read-only copy of the data, thereby safeguarding it from modifications or deletions.
When to use Hive “SNAPSHOT”?
The use of Hive’s “SNAPSHOT” feature can be particularly beneficial in scenarios such as:
- Consistent Reporting: Snapshots provide a consistent view of data, useful in generating reports that do not fluctuate due to underlying data changes.
- Debugging and Troubleshooting: When debugging complex processes or exploring anomalies in data, using a snapshot ensures you’re working with a fixed data set, making it easier to identify the issue.
- Archiving and Compliance: For organizations that need to comply with data archiving regulations, creating snapshots is an efficient way to store historical data.
- Disaster Recovery: Snapshots can act as a backup mechanism to restore data if a system failure or data corruption occurs.
Conversions in Hive “SNAPSHOT”
As of my knowledge cutoff in September 2021, Hive does not offer a built-in “SNAPSHOT” feature, nor direct conversion functionalities from snapshots to other forms. However, users often manage snapshots through Hive’s partitioning system, external tools, or Hadoop Distributed File System (HDFS) snapshot functionality, depending on their specific requirements.
Creating a Hive “SNAPSHOT” – A DDL and Insert Example
Given Hive’s absence of a direct “SNAPSHOT” feature, here is a workaround using Hive partitioning to effectively create a snapshot-like view of your data.
Let’s consider a table ‘sales’ that contains daily sales data.
CREATE TABLE sales (
product_id INT,
sale_date DATE,
quantity_sold INT,
sale_price DOUBLE
)
PARTITIONED BY (snapshot_date DATE);
Here, ‘snapshot_date’ is the partition field, which will help you create and segregate snapshots of your data. Now, suppose you want to take a snapshot of the sales data as of ‘2023-08-02’. You would create a new partition and load data into it as follows:
INSERT OVERWRITE TABLE sales PARTITION (snapshot_date='2023-08-02')
SELECT product_id, sale_date, quantity_sold, sale_price
FROM sales
WHERE sale_date <= '2023-08-02';
This would create a snapshot of all sales data up to and including ‘2023-08-02’. This partition would remain static unless you specifically overwrite or alter it, effectively acting as a snapshot.
Hive important pages to refer
