Re: can add a command "size" to see a key how it memory used?

[Didier Spezia]

Try the DEBUG OBJECT command: it returns the serialized length of a given key.

Regards,

Didier.

On Thursday, September 13, 2012 3:56:15 AM UTC+2, mike wrote:

can add a command "size" to see a key how it memory used?

[Ori Livneh]

Hi,

You can use the (undocumented, AFAIK) command DEBUG OBJECT key, and note the value of "serializedlength".

--
Ori Livneh
o...@wikimedia.org

On Wednesday, September 12, 2012 at 6:56 PM, mike wrote:

> can add a command "size" to see a key how it memory used?

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[Sripathi Krishnan]

I am afraid the serializedLength is a poor indicator of the actual memory used by the key. When an object is serialized, strings are compressed. Overheads due to pointers are no longer present in the serialized data. 

But there is a way to get a reasonable estimate of memory usage for a key. Use the dump command to generate a binary dump for the key. Then parse this dump using redis-rdb-tools to get a reasonable approximation of memory. 

redis-rdb-tools has 95% of the code to solve this; but it needs some glue code to work off any key on a live redis server. I have created https://github.com/sripathikrishnan/redis-rdb-tools/issues/13 to track this; I'll see if I can implement it this week.

--Sri

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[Sripathi Krishnan]

I added a new command redis-memory-for-key to rdbtools package. You will have to re-install redis-rdb-tools to run this command.

Notes from readme document : 

redis-memory-for-key person:1

redis-memory-for-key -s localhost -p 6379 -a mypassword person:1

Output :

Key             "person:1"
Bytes               111
Type                hash
Encoding            ziplist
Number of Elements      2
Length of Largest Element   8

NOTE :

1. This was added to redis-rdb-tools version 0.1.3
2. This command depends redis-py package

--Sri