Hive : Hive’s ACID properties and how can you implement them in a table?

One of the key features that makes Hive a powerful tool for big data analytics is the support for ACID properties. ACID stands for Atomicity, Consistency, Isolation, and Durability, and refers to a set of properties that ensure the reliability of database transactions. In this article, we’ll explore the role of Hive’s ACID properties and how to implement them in a table.

What are ACID Properties?

ACID properties refer to a set of properties that ensure that database transactions are reliable, consistent, and recoverable. The four properties that make up ACID are:

1. Atomicity: This property ensures that a transaction is treated as a single, indivisible unit of work. If any part of the transaction fails, the entire transaction is rolled back, ensuring that the database is left in a consistent state.
2. Consistency: This property ensures that a transaction brings the database from one valid state to another. In other words, the transaction cannot violate any of the rules or constraints that have been defined for the database.
3. Isolation: This property ensures that multiple transactions can run concurrently without interfering with each other. Each transaction is executed in isolation, so that the results of one transaction do not affect the results of another.
4. Durability: This property ensures that once a transaction is committed, it is permanent and cannot be lost due to hardware or software failure.

The Role of ACID Properties in Hive

Hive’s ACID properties are essential for ensuring data consistency and reliability in a distributed environment. Hive uses the ACID properties to provide transactional guarantees for data stored in tables. Hive’s ACID properties provide the following benefits:

1. Data Consistency: ACID properties ensure that data is consistent across all nodes in a distributed environment. This means that if a transaction is executed on one node, the results will be consistent across all other nodes in the cluster.
2. Data Integrity: ACID properties ensure that data is protected from accidental or malicious changes. Transactions are executed atomically, ensuring that the data remains in a consistent state at all times.
3. Data Recovery: ACID properties ensure that data can be recovered in the event of hardware or software failure. Transactions are durable, meaning that they are permanently recorded and can be restored if necessary.

How to Implement ACID Properties in a Hive Table

To implement ACID properties in a Hive table, you need to perform the following steps:

1. Enable ACID Properties: To enable ACID properties in a Hive table, you need to set the “transactional” property to true. This property can be set using the following command:

SET hive.txn.manager=org.apache.hadoop.hive.ql.lockmgr.DbTxnManager;

2. Create a Transactional Table: To create a transactional table, you need to use the “CREATE TABLE” statement with the “STORED AS” clause set to “ORC”. For example:

CREATE TABLE employees (
  id INT,
  name STRING,
  salary INT
)
CLUSTERED BY (id) INTO 10 BUCKETS
STORED AS ORC
TBLPROPERTIES ('transactional'='true');

3. Perform Transactions: To perform transactions on a transactional table, you need to use the “INSERT”, “UPDATE”, and “DELETE” statements. For example:

INSERT INTO employees (id, name, salary) VALUES (1, 'John Doe', 50000);

4. Commit Transactions: To commit a transaction, you need to use the “COMMIT” statement. For example:

COMMIT;