HMSET

Set multiple field-value pairs in the hash table simultaneously.

If the hash table does not exist, HMSET will first create an empty hash table and then perform the operation.

If the field already exists, the old value will be overwritten by the new value.

Redis Native Command Syntax

HMSET key field value [field value ...]

Parameter Description

• key: The key of the hash table
• field: The field in the hash table
• value: The value to set

Detailed Explanation

The HMSET command is used to set multiple field-value pairs in the hash table simultaneously. It is the batch version of the HSET command, which can set multiple fields at once, improving write efficiency.

Redisun Usage

In redisun, the HMSET command is implemented through the HmSetCommand class and the hmset method in the Redisun class.

Basic Usage

Redisun redisun = Redisun.create(options -> {
  options.setAddress("redis://127.0.0.1:6379");
});

// Prepare multiple field-value pairs
Map<String, String> userHash = new HashMap<>();
userHash.put("name", "Alice");
userHash.put("email", "alice@example.com");
userHash.put("age", "25");
userHash.put("city", "New York");

// Set multiple hash table fields simultaneously
boolean result = redisun.hmset("user:1000", userHash);
System.out.println("HMSET result: " + result); // Output: true

// Verify successful setting
System.out.println("Name: " + redisun.hget("user:1000", "name")); // Output: Alice
System.out.println("Email: " + redisun.hget("user:1000", "email")); // Output: alice@example.com

// Update some fields
Map<String, String> updateHash = new HashMap<>();
updateHash.put("age", "26");
updateHash.put("country", "USA");
result = redisun.hmset("user:1000", updateHash);
System.out.println("Update result: " + result); // Output: true

// Verify update results
System.out.println("Age: " + redisun.hget("user:1000", "age")); // Output: 26 (updated)
System.out.println("Country: " + redisun.hget("user:1000", "country")); // Output: USA
System.out.println("City: " + redisun.hget("user:1000", "city")); // Output: New York (unchanged)

// Asynchronous version
Map<String, String> asyncHash = new HashMap<>();
asyncHash.put("phone", "1234567890");
asyncHash.put("website", "https://example.com");
CompletableFuture<Boolean> future = redisun.asyncHmset("user:1001", asyncHash);
future.thenAccept(res -> System.out.println("Async HMSET result: " + res));

Notes

1. If the hash table does not exist, a new hash table will be automatically created
2. If the field already exists, the old value will be overwritten by the new value
3. If setting only one field-value pair, it is recommended to use the HSET command
4. The time complexity of the HMSET command is O(N), where N is the number of fields being set
5. Compared to calling HSET multiple times, HMSET can reduce the number of network round trips and improve performance
6. Suitable for batch setting multiple properties of an object
7. All field-value pairs are either all set successfully or all fail (atomic operation)

References

• Redis HMSET Command Official Documentation