Accessing the Ledger Database

Ledger has a database with access to potentially hundreds of thousands or even millions of data points. This page describes how you can make use of our database in your own mods

What about extensions?

The database extension API is extremely simple - it is designed to allow other database types, not actually accessing the databse

What language?

While we would strongly recommend Kotlin, which grants you access to all of our database methods, removing the need for an API, it is possible to write using Java with our LedgerApi. Please see the Java section.

Negatable parameters

When searching the database, some parameters can be negative. Making the world parameter negative, for example, would show all results where the world is not the one specified.

Kotlin

With Kotlin, you can access our database from within the Ledger coroutine.

object LedgerExamples {
    fun search(targetWorld: ServerWorld) {
        // We make a search parameters object showing results only in the world
        val params = ActionSearchParams.build {
            this.worlds = mutableSetOf(Negatable.allow(targetWorld.getRegistryKey().getValue()))
        }
        Ledger.launch {
            // Run the query and select actions on page 1
            val results: SearchResults = DataaseManager.searchActions(targetWorld)
            // Store the actions of the current page in a variable
            val actions: List<ActionType> = results.actions
        }
    }
    fun insert(world: World,
        player: PlayerEntity,
        pos: BlockPos,
        state: BlockState,
        context: ItemPlacementContext,
        entity: BlockEntity?) {
        // Create action object
        val action = ActionFactory.blockPlaceAction(world, pos, state, player, entity)
        // Insert action into the database
        ActionQueueService.addToQueue(action)
    }
}

Java

With Java, you can access our database with the API which can be obtained with Ledger.getApi(). You can see the API here.

public class LedgerExamples {
    public SearchResults getSearchResults(ServerWorld world) {
        // Create parameters
        ActionSearchParams.Builder params = new ActionSearchParams.Builder();
        Set<Negatable<Identifier>> worlds = new HashSet<>();
        worlds.add(Negatable.allow(world.getRegistryKey().getValue()));
        params.setWorlds(worlds);
        // Run search
        CompletableFuture<SearchResults> future = Ledger.getApi().searchActions(params.build(), 0);
        // Blocks thread for result
        SearchResults results = future.get();
    }

    public void insert(World world,
                       PlayerEntity player,
                       BlockPos pos,
                       BlockState state,
                       ItemPlacementContext context,
                       BlockEntity entity) {
        // Create action
        ActionType action = ActionFactory.INSTANCE.blockPlaceAction(world, pos, state, player, entity);
        // Log the action
        Ledger.getApi().logAction(action);
    }
}

Negatable

Normal behaviour: Negatable.allow(object)

Negative behaviour: Negatable.deny(object)

ActionSearchParams

This class is used for filtering searches.

Kotlin

Set the parameters when creating the ActionSearchParams.Builder object

Java

Use the setPropertyName method on the ActionSearchParams.Builder object

Current params:

min: BlockPos

Forms one corner of the cubic block selection

max: BlockPos

Forms the other corner of the cubic block selection

before: Instant

Selects all actions which occurred before the specified point in time

after: Instant

Selects all actions which occurred after the specified point in time

actions: MutableSet<Negatable<String>>

A list of action types with OR filtering if not negative and AND filtering if negative

objects: MutableSet<Negatable<Identifier>>

A list of identifiers containing object names, such as minecraft:diamond_ore. Uses OR filtering if not negative and AND filtering if negative

sourceNames: MutableSet<Negatable<String>>

A list of non-player source names, such as tnt, with OR filtering if not negative and AND filtering if negative

sourcePlayerNames: MutableSet<Negatable<String>>

A list of player names to filter by. Uses OR filtering if not negative and AND filtering if negative

worlds : MutableSet<Negatable<Identifier>>

A list of world identifiers to filter by. Uses OR filtering if not negative and AND filtering if negative