Re: querying vs using relationship list and iterate

From: Nishant Neeraj (nishant.has.a.questio..mail.com)
Date: Tue Jun 08 2010 - 15:11:51 UTC

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    Thanks Michael for the quick response.

    I was wondering which one will be less costlier to do? A join query(#2), or
    iterating over objects(#1)? And isn't iterating over objects need to pull
    each object from database before they can be compared?

    Thanks
    Nishant

    On Tue, Jun 8, 2010 at 8:25 PM, Michael Gentry <mgentr..asslight.net>wrote:

    > #2 won't work the way you want. It would need to be more along the lines
    > of:
    >
    > user = $testUser and user.memberships.group = $group
    >
    >
    > I've tended to use something closer to #1, but encapsulate it in my
    > User.java class as something like:
    >
    > public boolean isInGroup(String groupName)
    > {
    > for (Group g : getMemberships().getGroups())
    > if (groupName.equals(g.getName())
    > return true;
    > return false;
    > }
    >
    > That's pseudocode and unlikely to work, but should give you the
    > general idea. You can then say:
    >
    > if (myUser.isInGroup(testGroupName)) {...}
    >
    >
    > Thanks,
    >
    > mrg
    >
    >
    > On Tue, Jun 8, 2010 at 10:41 AM, Nishant Neeraj
    > <nishant.has.a.questio..mail.com> wrote:
    > > Hi,
    > >
    > > I have three tables USERS, MEMBERSHIPS, GROUPS -- where membership is a
    > > linking table that joins users and groups in many-to-many relationship,
    > and
    > > also stores users' role in the group.
    > >
    > > Sometime when I need to know whether a user exists in a group [or what
    > role
    > > a user has in a group], I can do it by two ways:
    > >
    > > 1. groups.getMembershipList() and iterate over the list inflating each
    > > member and comparing with the User object that is on test. like
    > >
    > > for(Membership m: g.getMembershipList())
    > > {
    > > if(m.getUser().equals(testUser)
    > > return true;
    > > }
    > >
    > > Or.
    > >
    > > 2. I can just write a query using Expression.
    > >
    > > Expression.forString(Membership.class, "user = $testUser and
    > group=$group");
    > >
    > >
    > > Can someone suggest which one is better approach? Or, is there a even
    > better
    > > third approach?
    > >
    > > Thanks
    > > Nishant
    > >
    >



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