redis计算指定key大小
memory usageredis4 及已上版本>SET""""OK> MEMORY USAGE ""(integer)51memoryusage 命令返回key和value占用内存的bytes--stat持续输出stats模式,在测试上可以做测试>redis-cli-apassword-p6379-hhostname--stat------- data ------ -----
memory usage
redis4 及已上版本
> SET "" ""
OK
> MEMORY USAGE ""
(integer) 51
memory usage 命令返回key和value占用内存的bytes
--stat
持续输出stats模式,在测试上可以做测试
> redis-cli -a password -p 6379 -h hostname --stat
------- data ------ --------------------- load -------------------- - child -
keys mem clients blocked requests connections
35768376 6.98G 2021 0 2600414876 (+3) 3121642
35768376 6.98G 2021 0 2600414879 (+3) 3121642
35768376 6.98G 2021 0 2600414884 (+5) 3121642
35768376 6.98G 2021 0 2600414887 (+3) 3121642
35768376 6.98G 2021 0 2600414890 (+3) 3121642
35768376 6.98G 2021 0 2600414894 (+4) 3121642
35768376 6.98G 2021 0 2600414898 (+4) 3121642
35768376 6.98G 2021 0 2600414901 (+3) 3121642
35768376 6.98G 2021 0 2600414905 (+4) 3121642
35768376 6.98G 2021 0 2600414909 (+4) 3121642
35768376 6.98G 2021 0 2600414912 (+3) 3121642
通过第三方工具rdbtools来计算key大小
安装pip
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
# 用相对应版本python安装对应版本
sudo python get-pip.py
sudo python3 get-pip.py
安装rdbtools
pip install rdbtools
查看指定key大小
redis-memory-for-key -s hostname [-a password] -p 6379 -d 0 key1
rdb
# rdb --help
usage: usage: rdb [options] /path/to/dump.rdb
Example : rdb --command json -k "user.*" /var/redis/6379/dump.rdb
positional arguments:
dump_file RDB Dump file to process
optional arguments:
-h, --help show this help message and exit
-c CMD, --command CMD
Command to execute. Valid commands are json, diff,
justkeys, justkeyvals, memory and protocol
-f FILE, --file FILE Output file
-n DBS, --db DBS Database Number. Multiple databases can be provided.
If not specified, all databases will be included.
-k KEYS, --key KEYS Keys to export. This can be a regular expression
-o NOT_KEYS, --not-key NOT_KEYS
Keys Not to export. This can be a regular expression
-t TYPES, --type TYPES
Data types to include. Possible values are string,
hash, set, sortedset, list. Multiple typees can be
provided. If not specified, all data types will be
returned
-b BYTES, --bytes BYTES
Limit memory output to keys greater to or equal to
this value (in bytes)
-l LARGEST, --largest LARGEST
Limit memory output to only the top N keys (by size)
-e {raw,print,utf8,base64}, --escape {raw,print,utf8,base64}
Escape strings to encoding: raw (default), print,
utf8, or base64.
-x, --no-expire With protocol command, remove expiry from all keys
-a N, --amend-expire N
With protocol command, add N seconds to key expiry
time
rdb -c memory /tmp/dump.rdb
database,type,key,size_in_bytes,encoding,num_elements,len_largest_element,expiry
0,hash,data:index_flow_yingshi,10492,hashtable,1,8992,2019-01-14T08:20:10.236000
0,hash,data:index_movie,22068,hashtable,7,2896,2019-01-14T07:29:19.685000
0,string,block:index_module_novel,8296,string,7694,7694,2019-01-13T00:27:46.128000
0,string,block:index_bottom_baike_aikan,8296,string,7632,7632,2019-01-14T02:27:11.850000
0,string,block:index_bottom_tools,5224,string,4549,4549,2019-01-13T01:02:09.171000
0,string,block:index_module_travel,7272,string,6408,6408,2019-01-13T00:43:39.478000
...
输出了db,数据类型,key, 大小, 编码等多列信息
在这种特殊的模式下,redis-cli会对key进行空间分析,扫描出占用空间大的key的集,并且提供关于数据类型和数组组成构造
只要知道最大的N个key, 可以使用-l选项
[@sjs_73_171 ~]$ rdb -c memory -l 3 /tmp/dump.rdb
database,type,key,size_in_bytes,encoding,num_elements,len_largest_element,expiry
0,hash,city_tong,724236,hashtable,3113,216,2019-01-14T01:10:59.407000
0,hash,iplocsearch,406292,hashtable,383,180190,2019-01-30T05:37:56.082000
0,hash,weather_tong3,583844,hashtable,319,1658,2019-01-07T10:22:33.742000
redis-cli --bigkeys
redis-cli -a password -p 6379 -h hostname --bigkeys
# Scanning the entire keyspace to find biggest keys as well as
# average sizes per key type. You can use -i 0.1 to sleep 0.1 sec
# per 100 SCAN commands (not usually needed).
[00.00%] Biggest string found so far '100000004602269' with 156 bytes
[00.00%] Biggest string found so far '100000006251981' with 225 bytes
[00.00%] Biggest string found so far '100000011594328' with 226 bytes
[00.00%] Biggest string found so far '100000000095649' with 227 bytes
[00.01%] Biggest string found so far '100000003257493' with 228 bytes
...
debug object key
redis的命令,可以查看某个key序列化后的长度。 例:
连接上redis后执行如下命令
b.redis:1959> hmset myhash k1 v1 k2 v2 k3 v3
OK
b.redis:1959> debug object myhash
Value at:0x7f005c6920a0 refcount:1 encoding:ziplist serializedlength:36 lru:3341677 lru_seconds_idle:2
Value at:key的内存地址
refcount:引用次数
encoding:编码类型
serializedlength:序列化长度
lru_seconds_idle:空闲时间
几个需要注意的问题 serializedlength是key序列化后的长度(redis在将key保存为rdb文件时使用了该算法),并不是key在内存中的真正长度。这就像一个数组在json_encode后的长度与其在内存中的真正长度并不相同。不过,它侧面反应了一个key的长度,可以用于比较两个key的大小。 serializedlength会对字串做一些可能的压缩。如果有些字串的压缩比特别高,那么在比较时会出现问题。比如下列:
b.redis:1959> set str1 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
OK
b.redis:1959> set str2 abcdefghijklmnopqrstuvwxyz1234
OK
b.redis:1959> debug object str1
Value at:0x7f007c035b80 refcount:1 encoding:embstr serializedlength:12 lru:3342615 lru_seconds_idle:13
b.redis:1959> debug object str2
Value at:0x7f00654df400 refcount:1 encoding:embstr serializedlength:31 lru:3342622 lru_seconds_idle:7
两个字串的实际长度都是30, 但str1的serializedlength为12, str2的为31。
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