When you have an entity resolution (slot-filling with SlotTypes that have the same synonyms) , how many AuthoritiesPerResolution are you able to have?
Is there any case where having multiple AuthoritiesPerResolution is possible?
What are the scenarios and conditions to get more than one AuthoritiesPerResolution?
Related
I want to create a sqlite database with at least two tables: account and service. One account can have several services and one service can be used by several accounts.
I would like to be able to query all the services which one account uses.
Now, where it gets complicated for me is that I would like to avoid a third table which is usually used - as far as I know - to resolve this many-to-many relationship.
Is there an appropriate way to do this?
Thank you!
You can denormalize your schema and store relations in a field containing an array in each table. But this is going to be less efficient to query and not all database engines support array type. Actually sqlite3 doesn't. You can mitigate that by storing that as a JSON data type which will be then an array in JSON representation.
Looking to see if it's possible to have a Rails app hit multiple dbs dynamically. To be more precise:
I have an app that can operate in different regions.
Each request that comes in will identify the region.
In mysql, one region corresponds to exactly one db.
The dbs are identical in terms of the schema. Implying the AR models are all the same, it's just that depending on the request, I want the model object to be retrieved/updated from one of the per region dbs.
All of the data is isolated to that particular db. There is never any crossover, nor any need to query multiple dbs at the same time.
One way to avoid multiple db's is to add a "region" column to all the models/tables (don't really like that).
Another way to do this would simply be to fire up different instances for different regions. Again, don't really want to do that given all the config overhead (cloud servers, nginx, etc, etc).
Any ideas?
I found that Rails 6.1 introduced the notion of horizontal sharding. That was what I needed. And I found this article useful:
https://www.freshworks.com/horizontal-sharding-in-a-multi-tenant-app-with-rails-61-blog/
In a Firebase social-media-esque app, here is how I'm storing groups along with its members:
Here, I have a reciprocating relationship in terms of memberships of groups. A group knows all of the users that are a part of it in group-users and vise-versa—a user knows all of the groups it's in via user-groups. The reason I thought to do this is it seems to be quick for a user to access all of its groups, and likewise it seems to be quick for a group to access all of its users. However, having this reciprocating data is costly in terms of space. My other option would be to keep just the user-groups node, and to retrieve all the members of a single group I would need to query that node by group ID. This option seems slower but would take less space in the database. Which option is more advised? Thanks.
The best data model always depends on the use-cases of your app. If you need access to both the groups-for-a-user and the users-for-a-group, the cheapest way to do so is to store both.
See:
Many to Many relationship in Firebase
the answer to this question in a video
this article about NoSQL data modeling
the Firebase video series Firebase for SQL developers
So I have a question about designing a datastore database, I'm using objectify. I'm trying to get optimal performance.
So I need to create two entities, List and Listings, with a relationship. There will be 500,000 listings in all and 50,000 per list.
Looking at this https://code.google.com/p/objectify-appengine/wiki/IntroductionToObjectify#Multi-Value_Relationship
I see there are three methods to store relationship.
One to one, many to one and Multi-value relationship.
The Multi-Value relationship looks like it would work great but appears to have a limit of 5,000 entries per entity(List?)
So I assume I should use the many to one method but I question the performance on this as I would have to query every listing and filter.
Can I have good performance doing what I'm attempting with datastore?
Any help at all would be great!
Multi-value relationship in that case has no a good performance because each value implies a new line on its field index. It means longer write times. Also it has a limit of entries. It's useful when you have a few values to store.
There is another type of relationship: entity group.
The criteria to choose between each method also depends on the type of queries you do and the frequency of updating entities.
In base of the information you provide, I recommend many-to-one relationship.
I've seen examples of ACL to deal with one entity but none to deal with fetching multiple items - such as a list of posts that belong to an author. One (bad) suggestion was to fetch all the items and then filter using acl - not going to work when we have a million items. What is the intended way to fetch multiple items - let's say I want to fetch all my posts (using any criteria I need such as published or ordered by) in batches of 50 for the pager (another reason why post filtering will not work - I'd end up with different page sizes).
I think, you shouldn't use ACL for determining which posts belong to a particular author because ACL is about access control / permissions, not about finding owners or determining object relations.
But certainly, you are perfectly ok to want to get a list of posts certain user can view, edit or moderate for example.
Currently, there is no functionality to do this on API level, but... well, I think in Symfony2 / Doctrine2 you can just do Native Query and join with acl_entries table.
But there is a drawback. In a large system acl_entries table will contain just too much rows and joining against it can be slow (we know, that MySQL is stupid sometimes). So you might also want to build some kind of caching system around this.