Storage Plan: Map v/s linear

[Brian Beuning]

I suggest worrying about your DB schema first.
Do you want person^2 entries in your DB?
Once you settle on your DB schema, then just mirror it in memcached.
Are connections reflexive?  If A is a friend of B, does that imply B is a
friend of A?
 
I think any DBA would like option 2 better.
 
Brian Beuning
 
SHARED
 
create table People (
    personID int,
    name varchar(50),
    -- more personal info columns
    primary key (personID)
)
 
OPTION 1 
 
create table Relations (
    Aid int,
    data blob,    -- contains HashMap table
    primary key (Aid)
)
 
OPTION 2
 
create table Relations (
    Aid int,
    Bid int,
    type int,
    primary key (Aid, Bid)
)

-----Original Message-----
From: Rakesh Rajan [mailto:rakeshxp at gmail.com]
Sent: Saturday, November 10, 2007 7:14 AM
To: memcached at lists.danga.com
Subject: Storage Plan: Map v/s linear


Hi Folks,

I am trying to use memcached to store the relationships between persons ( So
person A -> Relationship Type -> Person B )  ( Java based solution )

So given a person, I would need 
1) To see if another person is a connection 
2) And the connection type.

As I see it, I could implement this in 2 ways

OPTION 1

For each user store a HashMap of  personID,relationshipType. 
e.g
            Map<Integer,Integer> relationMap = new
HashMap<Integer,Integer>(); 
            relationMap.put(1,1); .......

            memcache.put( "prefix" + sourcePersonID ,  relationMap);

In this case, there would be as many keys in memcached, as there are
persons.


OPTION 2
 
    Use both person IDs in the memcahe key.
   e.g
        memcache.put( "prefix" + sourcePersonID + ":"+ targetPersonID ,
relationType);

In this case, there would be at max persons^2  keys in memcahed. 


Assumptions
1) Each person would have an average of 200-300 friends
2) Memcahed would be on a different set of servers compared to the webapps (
So there would be a N/W delay in passing the data from memcached -> webapp )


I would like to know which of option is better for my requirement ? 

Thanks,
Rakesh


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