hi All:
As we know the reality has never been perfect, i am working on a legacy
system with bad designed DB tables and i can't modify the tables for some
reason, i can only read. On perfect situation, Entity A has a list of Entity
B (both mapped as MySql table with 1:n relationship), when one would like to
get A with B, a simple RequestFactory call will do that:
em.findAs().with('bs').fire(....);
but the reality is that the A table does not has any relationship with B
table, instead A table has a String column which store the B table item ids.
can you imagine that? Now i want to get A with B, my plan is:
1. get the A entity using em.findA();
2. parse A's String field who contains many B's IDs, now i get: List<Long>
ids.
3. iterator the id list, find allB entities.
4. store the list of B entities in A's list field. and return.
should work. but there is one problem: performance, often one A has many Bs
references to it(say 100), if the web client want to get 10 A, then i have
to do 10*100+1 times DB read operations.
my solution:
1. Cache all Bs in server memory and refer to it when i'd like to get it.
2. i notice that when the client want to get a list of A, there is no need
to append Bs(findAllAs()), but if it want to get only one A that means the
user want to see the details of A, i must append all Bs with A to the
client.
Now problems comes, how can i distinguish the operation is getAllAs(int
start, int size) or getA(Long id)? because the getAllAs(int start, int size)
method also call getA(Long id).
i just using RequestFactory a few days and not quite familiar with it. hope
somebody can help me with the solution.
Many thanks.
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