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How to atomically delete keys matching a pattern using Redis
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Starting with redis 2.6.0, you can run lua scripts, which execute atomically. I have never written one, but I think it would look something like this
EVAL "return redis.call('del', unpack(redis.call('keys', ARGV[1])))" 0 prefix:[YOUR_PREFIX e.g delete_me_*]
Warning: As the Redis document sa...
BLE协议—广播和扫描 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...广播方式的报文有4种，分别为可连接的非定向广播（ADV_IND）、可连接的定向广播（ADV_DIRECT_IND）、可扫描非定向广播（ADV_SCAN_IND）、不可连接的非定向广播（ADV_NONCONN_IND）
4种广播的使用场景各不相同
可连接的非定向广播（A...
@UniqueConstraint annotation in Java
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@Entity
@Table(uniqueConstraints={@UniqueConstraint(columnNames = {"id_1" , "id_2"})})
public class class_name {
@Id
@GeneratedValue
public Long id;
@NotNull
public Long id_1;
@NotNull
public Long id_2;
}
Hope it helped.
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Foreign keys in mongo?
...his:
class Student
include Mongoid::Document
field :name
embeds_many :addresses
embeds_many :scores
end
class Address
include Mongoid::Document
field :address
field :city
field :state
field :postalCode
embedded_in :student
end
class Score
include Mongoi...
When and why will a compiler initialise memory to 0xCD, 0xDD, etc. on malloc/free/new/delete?
...----- -------- -------------------------
0xCD Clean Memory Allocated memory via malloc or new but never
written by the application.
0xDD Dead Memory Memory that has been released with delete or free.
It is used to detect w...
Add a new item to a dictionary in Python [duplicate]
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default_data['item3'] = 3
Easy as py.
Another possible solution:
default_data.update({'item3': 3})
which is nice if you want to insert multiple items at once.
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What is a bus error?
... when your processor cannot even attempt the memory access requested, typically:
using a processor instruction with an address that does not satisfy its alignment requirements.
Segmentation faults occur when accessing memory which does not belong to your process, they are very common and are typ...
How can I store my users' passwords safely?
...tials';
}
(In case you are still using legacy 5.3.7 or newer you can install ircmaxell/password_compat to have access to the build-in functions)
Improving upon salted hashes: add pepper
If you want extra security, the security folks now (2017) recommend adding a 'pepper' to the (automatically)...
MySQL Removing Some Foreign keys
...You can use this to find foreign key constraints: SELECT * FROM information_schema.table_constraints WHERE constraint_schema = '<your db name>' AND constraint_type = 'FOREIGN KEY'
– Gayan Dasanayake
Aug 26 '17 at 2:48
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Mysql: Select rows from a table that are not in another
How to select all rows in one table that do not appear on another?
8 Answers
8
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