Skip to content

Latest commit

 

History

History
111 lines (79 loc) · 3.61 KB

overview-5-common-operations.md

File metadata and controls

111 lines (79 loc) · 3.61 KB

Redis cheatsheet

APPEND key value

redis> EXISTS mykey
(integer) 0
redis> APPEND mykey "Hello"
(integer) 5
redis> APPEND mykey " World"
(integer) 11
redis> GET mykey
"Hello World"

The EXISTS command is used to check whether a key exists in the database or not. The command takes one or more keys as arguments and returns an integer value:

  • 1 if the key exists.
  • 0 if the key does not exist.

image

And The APPEND command is used to append a value to an existing key's value. If the key does not exist, a new key is created, and the value is set. The APPEND command is specifically designed for string values.

image

BITCOUNT key [start end]

redis> SET mykey "foobar"
"OK"
redis> BITCOUNT mykey
(integer) 26
redis> BITCOUNT mykey 0 0
(integer) 4
redis> BITCOUNT mykey 1 1
(integer) 6

In the given example, a Redis key named "mykey" is set to the string value "foobar." Subsequently, the BITCOUNT command is used to count the number of set bits (bits with a value of 1) in the binary representation of the value associated with "mykey." The BITCOUNT command allows you to count bits in the whole value or within a specified range.

Let's break down each part of the example:

  1. Setting the Key:

    redis> SET mykey "foobar"
"OK"

    This sets the value of the key "mykey" to the string "foobar" and returns "OK" to indicate that the operation was successful.

  2. Using BITCOUNT on the Entire Value:

    redis> BITCOUNT mykey
(integer) 26

    The BITCOUNT command without a range counts all the set bits in the binary representation of the value associated with "mykey." In this case, the binary representation of "foobar" contains 26 set bits.

  3. Using BITCOUNT within a Specific Range:

    redis> BITCOUNT mykey 0 0
(integer) 4

    Here, the BITCOUNT command is used with a range specified as 0 to 0. This counts the set bits in the first bit of the binary representation, resulting in 4 set bits.

    redis> BITCOUNT mykey 1 1
(integer) 6

    Similarly, this BITCOUNT command is used with a range specified as 1 to 1, counting the set bits in the second bit of the binary representation, resulting in 6 set bits.

In summary, the BITCOUNT command in this context is used to analyze the binary representation of the string value "foobar" and count the number of set bits in the entire value or within specific ranges. This can be useful for various applications such as bit-level manipulations or counting specific patterns in binary data.

Redis supports a variety of commands for interacting with its data store. Here are some common Redis operations grouped by functionality:

Hash Operations:

  • HSET key field value: Set the value of a hash field.

    Example:

    HSET myhash field1 "value1"

  • HGET key field: Retrieve the value of a hash field.

    Example:

    HGET myhash field1

Other Operations:

  • FLUSHALL: Remove all keys from all databases.

    Example:

    FLUSHALL

  • KEYS pattern: Get all keys matching a pattern.

    Example:

    KEYS *

These are just a few examples of common Redis operations. Redis provides a rich set of commands that cover various data structures and functionalities. Depending on your use case, you may explore more advanced commands and features that Redis offers.