Redis -- three special data types

 

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Catalog

One 、HyperLogLog Base Statistics

1.1 What is the cardinality ？

1.2  Benefits of using cardinality statistics

1.3 Application scenarios

1.4 matters needing attention  

1.5 Basic commands

1.6  Use

Two 、Geospatial Location

2.1 Introduce

2.2  Use scenarios

2.3 Basic commands

2.4 Explain in detail

2.4.1 GEOADD

2.4.2 GEOPOS

2.4.3 GEODIST

2.4.4 GEORADIUS

2.4.5 GEORADIUSBYMEMBER

2.4.6 GEOHASH

2.4.7 ZRANGE

2.4.8 ZREM

3、 ... and 、BitMap

  Introduce

Application scenarios

  Use

Summary

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One 、HyperLogLog Base Statistics

1.1 What is the cardinality ？

We can understand what is... Directly through an example Base Statistics , Like data sets {1, 2, 3, 3, 5, 5,}, So the cardinality set of this dataset is {1,2,3,5}, base ( Don't repeat elements ) by 4. That is to say The number of non repeating elements .

1.2  Benefits of using cardinality statistics

Every HyperLogLog Keys only cost 12 KB Memory , So we can calculate the proximity 2^64 Cardinality of different elements . This is the same as calculating the cardinality , The more elements consume memory, the more collections there are . If you want to from Memory angle To compare Hyperloglog First choice .

1.3 Application scenarios

    Web page uv（ A person visits a website many times , But still be a person ）

•   The traditional way ：set（ because set No repetition , If it repeats, it will overwrite ） Save the user's id, And then you can count ,set The number of elements in is used as the standard judgment , This way, if you save a large number of users id, It will be more troublesome and occupy a lot of memory in large websites . Here's what we're trying to do To count , Instead of saving users id.
•   Use HyperLogLog： One HyperLogLog The key only needs to be 12KB, The number that can be calculated is very huge , The occupied memory space is greatly reduced .

1.4 matters needing attention  

If Allow fault tolerance (0.81% Error rate , Counting can be ignored ）, Then it must be possible to use Hyperloglog！ If fault tolerance is not allowed , Just use set Or your own data type ！

 

1.5 Basic commands

Serial number	Command and description
1	PFADD key element [element ...] Add specified elements to HyperLogLog in .​
2	PFCOUNT key [key ...] Return to a given HyperLogLog The base estimate of .​
3	PFMERGE destkey sourcekey [sourcekey ...] Will be multiple HyperLogLog Merge into one HyperLogLog​

1.6  Use

127.0.0.1:6379> pfadd mykey1 a b c d e f   # Add data to the first group 
(integer) 1
127.0.0.1:6379> pfcount mykey1  # Statistics mykey1 Base number of 
(integer) 6
127.0.0.1:6379> pfadd mykey2 e e f j  # Add data to the second group 
(integer) 1
127.0.0.1:6379> pfcount mykey2     # Statistics mykey2 Base number of 
(integer) 3
127.0.0.1:6379> pfmerge mykey3 mykey1 mykey2   #  Combine the two groups  mykey1 mykey2 => mykey3  Combine 
OK
127.0.0.1:6379> pfcount mykey3    # Statistics mykey3 Base number of 
(integer) 7

Two 、Geospatial Location

2.1 Introduce

Redis3.2 The release of the Geospatial, It can be calculated Geographic information , The distance between the two places , People in a few miles around .

2.2  Use scenarios

  Friend orientation

  Check out the people around

  Taxi distance calculation

2.3 Basic commands

Serial number	Command and description
1	GEOADD key longitude latitude Location name Geospatial location to be specified （ latitude 、 longitude 、 name ） Add to specified key in
2	GEOPOS key Location name from key Returns the location of all the positioning elements （ Longitude and latitude ）.
3	GEODIST key place 1 place 2 Company Returns the distance between two given positions , If one of the two positions does not exist , Then the command returns a null value .
4	GEORADIUS key longitude latitude   Range value Company Centered on a given latitude and longitude , Find the elements in a certain radius
5	GEORADIUSBYMEMBER  key place   Distance value   Company Find the elements in the specified range , The center point is determined by a given location element
6	GEOHASH  key place 1   place 2 Will return 11 A character Geohash character string , If the two strings are closer , So the closer we get .
7	zrange  key  start stop Get assigned key Coordinate information in
8	zrem  key place Delete the specified key Specify the data of the target

Inquire the longitude and latitude of the place ：

City longitude and latitude query - Online query tool for longitude and latitude of domestic cities

2.4 Explain in detail

2.4.1 GEOADD

effect ： Add location

The rules ： Two levels cannot be added directly , We usually download city data , Directly through java The program is imported once ！

grammar ：GEOADD key longitude latitude Location name

  matters needing attention

Effective longitude from -180 C to 180 degree .

Effective latitude from -85.05112878 C to 85.05112878 degree .

When the coordinate position exceeds the specified range above , The command will return an error .

  Use

# Add a single message 
127.0.0.1:6379> geoadd address 116.708463 23.37102 shantou   
(integer) 1
# Add more information 
127.0.0.1:6379> geoadd address 116.405285 39.904989 beijin 121.472644 31.231706 shanghai
(integer) 2

2.4.2 GEOPOS

effect ： Get the location information of the designated place （ Longitude and latitude ）

grammar ：GEOPOS key Location name

  Use

127.0.0.1:6379> geopos address beijin   # Get the geographical location of Beijing 
1) 1) "116.40528291463851929"  # longitude 
   2) "39.9049884229125027"   # latitude 

2.4.3 GEODIST

effect ： Returns the distance between two given positions , If one of the two positions does not exist , Then the command returns a null value .

grammar ：GEODIST key place 1 place 2 Company

  Unit parameter ：

m Expressed in meters .
km Expressed in kilometers .
mi In miles .
ft In feet .
If the user does not explicitly specify the unit parameter , that GEODIST The default is meters As a unit .

  Use ：

127.0.0.1:6379> geodist address beijin shanghai km  # Check the distance between Beijing and Shanghai 
"1067.5980"

2.4.4 GEORADIUS

effect ： Centered on a given latitude and longitude , Find the elements in a certain radius .

grammar ：GEORADIUS key longitude latitude   Range value   Company

  Use ：

# Looking to 116,39 This longitude and latitude are the center , Looking for a square circle 1500km In the city 
127.0.0.1:6379> georadius address 116 39 1500 km
1) "shanghai"
2) "beijin"

#  Show the position to the middle distance 
127.0.0.1:6379> georadius address 116 39 1500 km withdist
1) 1) "shanghai"
   2) "996.7313"
2) 1) "beijin"
   2) "106.5063"

# Show other people's location information 
127.0.0.1:6379> georadius address 116 39 1500 km withcoord
1) 1) "shanghai"
   2) 1) "121.47264629602432251"
      2) "31.23170490709807012"
2) 1) "beijin"
   2) 1) "116.40528291463851929"
      2) "39.9049884229125027"

# Filter out the nearest city and show its distance 
127.0.0.1:6379> georadius address 116 39 1500 km withdist withcoord count 1
1) 1) "beijin"
   2) "106.5063"
   3) 1) "116.40528291463851929"
      2) "39.9049884229125027"


# Filter the nearest two cities and show their distance 
127.0.0.1:6379> georadius address 116 39 1500 km withdist withcoord count 2
1) 1) "beijin"
   2) "106.5063"
   3) 1) "116.40528291463851929"
      2) "39.9049884229125027"
2) 1) "shanghai"
   2) "996.7313"
   3) 1) "121.47264629602432251"
      2) "31.23170490709807012"

2.4.5 GEORADIUSBYMEMBER

effect ： Find the elements in the specified range , The center point is determined by a given location element .

grammar ：GEORADIUSBYMEMBER  key place   Distance value   Company

  Use ：

# Find out the distance from Beijing 1500km The city inside 
127.0.0.1:6379> georadiusbymember address beijin 1500 km
1) "shanghai"
2) "beijin"

 

2.4.6 GEOHASH

effect ： Will return 11 A character Geohash character string , If the two strings are closer , So the closer we get .

grammar ：GEOHASH  key place 1   place 2

  Use ：

127.0.0.1:6379> geohash address beijin shantou
1) "wx4g0b7xrt0"
2) "ws4uzy8d030"

2.4.7 ZRANGE

effect ： Get assigned key Coordinate information in .

grammar ：zrange  key  start stop

  Use ：

127.0.0.1:6379> zrange address 0 -1
1) "shantou"
2) "shanghai"
3) "beijin"

 

2.4.8 ZREM

effect ： Delete the specified key Specify the data of the target .

grammar ：zrem  key place

  Use ：

127.0.0.1:6379> zrem address shanghai
(integer) 1

3、 ... and 、BitMap

  Introduce

BitMap It's through One bit position To represent the corresponding value or state of an element , Only 0 and 1 Two states , Among them key It's the corresponding element itself .365 God = 365 bit ,1 byte = 8bit , That is to say, it only needs 46 In bytes or so , So it can Save a lot of space .

Application scenarios

（1） User check-in

（2） Count active users

（3） User online status （ Online is set to 1, If you are not online, set it to 0）

  Use

  demand ： Record Clock in from Monday to Sunday

1： Indicates that there is a clock out

0： It means you didn't punch in

127.0.0.1:6379> setbit sign 0 1
(integer) 0
127.0.0.1:6379> setbit sign 1 1
(integer) 0
127.0.0.1:6379> setbit sign 2 0
(integer) 0
127.0.0.1:6379> setbit sign 3 1
(integer) 0
127.0.0.1:6379> setbit sign 4 1
(integer) 0
127.0.0.1:6379> setbit sign 5 0
(integer) 0
127.0.0.1:6379> setbit sign 6 0
(integer) 0

  Check to see if there is a clock out on a certain day

127.0.0.1:6379> getbit sign 3
(integer) 1
127.0.0.1:6379> getbit sign 6
(integer) 0

  Count the clocking records of this week

127.0.0.1:6379> bitcount sign
(integer) 4

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Summary

That's all 【 One heart classmate 】 Organized 【Redis】 Medium 【 Three special data types 】, Maybe we seldom use , But if we can use it , Then its effect on us is very big , You can give us 【 Save huge space 】 as well as 【 Bring extremely fast speed 】.

If this article 【 article 】 It helps you , I hope I can give 【 One heart classmate 】 Order one Fabulous , It's not easy to create , Compared with the official statement , I prefer to use 【 Easy to understand 】 To explain every point of knowledge with your writing , If there is a pair of 【 back-end technology 】 Interested little cute , You are welcome to pay attention to ️️️ 【 One heart classmate 】️️️, I will bring you great 【 Harvest and surprise 】！