Struct NamedGraph 

pub struct NamedGraph { /* private fields */ }

A named graph in terminus-store.

Named graphs in terminus-store are basically just a label pointing to a layer. Opening a read transaction to a named graph is just getting hold of the layer it points at, as layers are read-only. Writing to a named graph is just making it point to a new layer.

Implementations

impl NamedGraph

pub fn name(&self) -> &str

Returns the label name itself.

pub async fn head_version(&self) -> Result<(Option<StoreLayer>, u64)>

Returns the layer this database points at, as well as the label version.

pub async fn head(&self) -> Result<Option<StoreLayer>>

Returns the layer this database points at.

Examples found in repository

examples/print_graph.rs (line 15)

async fn print_graph(store_path: &str, graph: &str) -> io::Result<()> {
    let store = open_directory_store(store_path);
    let graph = store
        .open(graph)
        .await?
        .expect(&format!("expected graph {} to exist", graph));

    match graph.head().await? {
        Some(layer) => {
            for id_triple in layer.triples() {
                // triples are retrieved in their id form. For printing,
                // we need the string form. The conversion happens here.
                let triple = layer
                    .id_triple_to_string(&id_triple)
                    .expect("expected id triple to be mapable to string");

                println!(
                    "{}, {}, {} {:?}",
                    triple.subject,
                    triple.predicate,
                    match triple.object {
                        ObjectType::Node(_) => "node",
                        ObjectType::Value(_) => "value",
                    },
                    match triple.object {
                        ObjectType::Node(n) => String::make_entry(&n),
                        ObjectType::Value(v) => v,
                    }
                );
            }
        }
        None => {}
    }

    Ok(())
}

examples/write_to_graph.rs (line 64)

async fn process_commands(store_path: &str, graph: &str) -> io::Result<()> {
    let store = open_directory_store(store_path);
    let graph = store
        .open(graph)
        .await?
        .expect(&format!("expected graph {} to exist", graph));

    // There are two types of builders. One creates a new base layer,
    // which has no parent. The other creates a child layer, which has
    // another layer as its parent.
    let builder = match graph.head().await? {
        Some(layer) => layer.open_write().await?,
        None => store.create_base_layer().await?,
    };
    let mut stdin = io::BufReader::new(io::stdin()).lines();

    while let Some(line) = stdin.next_line().await? {
        let segment = line.trim();
        if segment.len() == 0 {
            continue;
        }

        let command = parse_command(segment).await?;

        // add all the input data into the builder.
        // The builder keeps an in-memory list of added and removed
        // triples. If the same triple is added and removed on the
        // same builder, it is a no-op. This is even the case when it
        // is then later re-added on the same builder.
        //
        // Since no io is happening, adding triples to the builder is
        // not a future.
        match command {
            Command::Add(triple) => builder.add_value_triple(triple)?,
            Command::Remove(triple) => builder.remove_value_triple(triple)?,
        }
    }

    // When commit is called, the builder writes its data to
    // persistent storage.
    let layer = builder.commit().await?;

    // While a layer exists now, it's not yet attached to anything,
    // and is therefore unusable unless you know the exact identifier
    // of the layer itself. To make this the graph data, we have to
    // set the grap head to this layer.
    graph.set_head(&layer).await?;

    println!(
        "Added: {}, removed: {}",
        layer.triple_layer_addition_count().await?,
        layer.triple_layer_removal_count().await?
    );

    Ok(())
}

pub async fn set_head(&self, layer: &StoreLayer) -> Result<bool>

Set the database label to the given layer if it is a valid ancestor, returning false otherwise.

Examples found in repository

examples/write_to_graph.rs (line 100)

async fn process_commands(store_path: &str, graph: &str) -> io::Result<()> {
    let store = open_directory_store(store_path);
    let graph = store
        .open(graph)
        .await?
        .expect(&format!("expected graph {} to exist", graph));

    // There are two types of builders. One creates a new base layer,
    // which has no parent. The other creates a child layer, which has
    // another layer as its parent.
    let builder = match graph.head().await? {
        Some(layer) => layer.open_write().await?,
        None => store.create_base_layer().await?,
    };
    let mut stdin = io::BufReader::new(io::stdin()).lines();

    while let Some(line) = stdin.next_line().await? {
        let segment = line.trim();
        if segment.len() == 0 {
            continue;
        }

        let command = parse_command(segment).await?;

        // add all the input data into the builder.
        // The builder keeps an in-memory list of added and removed
        // triples. If the same triple is added and removed on the
        // same builder, it is a no-op. This is even the case when it
        // is then later re-added on the same builder.
        //
        // Since no io is happening, adding triples to the builder is
        // not a future.
        match command {
            Command::Add(triple) => builder.add_value_triple(triple)?,
            Command::Remove(triple) => builder.remove_value_triple(triple)?,
        }
    }

    // When commit is called, the builder writes its data to
    // persistent storage.
    let layer = builder.commit().await?;

    // While a layer exists now, it's not yet attached to anything,
    // and is therefore unusable unless you know the exact identifier
    // of the layer itself. To make this the graph data, we have to
    // set the grap head to this layer.
    graph.set_head(&layer).await?;

    println!(
        "Added: {}, removed: {}",
        layer.triple_layer_addition_count().await?,
        layer.triple_layer_removal_count().await?
    );

    Ok(())
}

pub async fn force_set_head(&self, layer: &StoreLayer) -> Result<()>

Set the database label to the given layer, even if it is not a valid ancestor.

pub async fn force_set_head_version( &self, layer: &StoreLayer, version: u64, ) -> Result<bool>

Set the database label to the given layer, even if it is not a valid ancestor. Also checks given version, and if it doesn’t match, the update won’t happen and false will be returned.

pub async fn delete(&self) -> Result<()>

Trait Implementations

impl Clone for NamedGraph

fn clone(&self) -> NamedGraph

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.