[redis] hash type

---

---

Hash type

Hash type , Also called hash , Its value It's an unordered Dictionary , Be similar to java Medium HashMap.

Compared with String Type serializes the object to Json character string , It is not very convenient to modify a field ; and Hash Structure can store each field in the object independently , You can do this for a single field CRUD：

The basic general commands are shown in the figure above , Here is a detailed introduction ！

1.1 HSET & HGET & HMSET & HMGET

• HSET key field value: Add or modify hash type key Of field Value

• HGET key field: Get one hash type key Of field Value

• HMSET: Batch add multiple hash type key Of field Value

• HMGET: Get more than one in batch hash type key Of field Value

You can see Hash Type implements a further layer of structured storage

• In batch processing, the attribute implementation for a single object is each field

  

Return to the top

---

1.2 HGETALL & HKEYS & HVALS

• HGETALL: Get one hash Type of key All of them field and value
• HKEYS: Get one hash Type of key All of them field
• HVALS: Get one hash Type of key All of them value

Return to the top

---

1.3 HINCRBY & HINCEBYFLOAT

• HINCRBY: The number stored at the field in the hash stored at the increment key . If the key does not exist , A new key containing the hash will be created . If the field does not exist , Set the value to before performing the operation 0.
• HINCEBYFLOAT: In specified increments , The specified field stored at the key and representing the hash of the floating-point number increment. If the increment value is negative , The result is that the hash field value decreases , Not incremental . If one of the following occurs , Returns an error ： This field contains a value of the wrong type （ It's not a string ）; The current field content or the specified increment cannot be parsed as a double precision floating-point number .

Return to the top

---

1.4 HSETNX

Only if the field does not already exist , Will be stored in key to value The field in the hash at is set to . If the key does not exist , A new key containing the hash will be created . If the field already exists , Then this operation is invalid .

• 1 If the field is a new field in the hash and the value is set .
• If a field already exists in the hash and no action is taken , Then for 0.
  

Return to the top

---

1.5 HSTRLEN & HLEN

• HSTRLEN: Get one hash Type of key The length of the median
• HLEN: Get one hash Type of key All of them field Size

Return to the top

---