I have two unrelated questions:
1. Error handling
Neither org.dataloader.BatchLoader::load nor org.dataloader.BatchLoaderWithContext::load allow one to throw an exception while attempting to fetch some data from some source, because the interface does not declare that an exception is thrown:
CompletionStage<List<V>> load(List<K> keys);
What is the correct way to handle an error, when, for example, my repository blows up while trying to load a list of entities by the provided keys? Similarly, what if some external HTTP request to fetch a list of entities fails in an unrecoverable way? It seems wrong in these cases to return an empty list; I would prefer to throw an exception and cause the entire GraphQL call stack to unwind instead of returning partial data.
2. Field selection
The BatchLoaderEnvironment passed to a BatchLoaderWithContext::load call does not allow me to inspect the request for the selected fields that caused loading of some entities to occur. Is there a way to do this? I prefer to select only the columns absolutely necessary from the database/API/etc. to optimize performance.
I can imagine that it may be difficult to traverse all nodes on the query to aggregate the minimum acceptable selection of fields from a given type, but it doesn't seem impossible. What I'm hoping is possible is something like this:
Given a query like this:
query {
foo {
bar {
fieldA
fieldB
fieldC
}
}
bar {
fieldA
fieldD
}
}
...that I can be able to then only select fields A, B, C, and D, instead of a SELECT * (assuming a relational database is the backing store).
Thanks for your help!
I have two unrelated questions:
1. Error handling
Neither
org.dataloader.BatchLoader::loadnororg.dataloader.BatchLoaderWithContext::loadallow one to throw an exception while attempting to fetch some data from some source, because the interface does not declare that an exception is thrown:What is the correct way to handle an error, when, for example, my repository blows up while trying to load a list of entities by the provided keys? Similarly, what if some external HTTP request to fetch a list of entities fails in an unrecoverable way? It seems wrong in these cases to return an empty list; I would prefer to throw an exception and cause the entire GraphQL call stack to unwind instead of returning partial data.
2. Field selection
The
BatchLoaderEnvironmentpassed to aBatchLoaderWithContext::loadcall does not allow me to inspect the request for the selected fields that caused loading of some entities to occur. Is there a way to do this? I prefer to select only the columns absolutely necessary from the database/API/etc. to optimize performance.I can imagine that it may be difficult to traverse all nodes on the query to aggregate the minimum acceptable selection of fields from a given type, but it doesn't seem impossible. What I'm hoping is possible is something like this:
Given a query like this:
...that I can be able to then only select fields A, B, C, and D, instead of a
SELECT *(assuming a relational database is the backing store).Thanks for your help!