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Blockchain components

cd rell/src

The key components of the blockchain dapp​

Import the ft4 library to utilize the pagination utility.

title: "./chroma.yml"
libs:
  ft4:
    registry: https://gitlab.com/chromaway/ft4-lib.git
    path: rell/src/lib/ft4
    tagOrBranch: v1.0.0r
    rid: x"FA487D75E63B6B58381F8D71E0700E69BEDEAD3A57D1E6C1A9ABB149FAC9E65F"
    insecure: false

The entity named product defines a structure similar to a relational database table for storing data that will be analyzed.

title: "./main.rell"
entity product {
    name: text;
    description: text;
    quantity: integer;
    price: integer;
}

The operation) named seed_data is responsible for creating a list of products. The key feature here is the batch creation of entities, which is executed with the statement create product (batch);.

./main.rell
operation seed_data() {
    // 100 bytes
    val name = "UltraPure Hydro Flask ProMax: Advanced Insulated Stainless Steel Bottle for Active and Everyday Use.";
    // 500 bytes
    val description = "Introducing the EcoSmart Water Bottle – your ultimate hydration companion! Made from premium, BPA-free materials, this bottle is designed for both functionality and style. With double-wall insulation, it keeps your beverages icy cold for up to 24 hours or piping hot for up to 12 hours. Its sleek, ergonomic design fits perfectly in your hand or cup holder. Featuring a leak-proof lid and a wide  mouth for easy cleaning or adding ice cubes, it’s perfect for gym sessions, hikes, or daily  commutes. Stay refreshed and eco-friendly with EcoSmart!";
    // in total a size of 1 object is going to be 616 bytes

    val batch_amount = 10; // amount of batches created
    val batch_size = 10000; // the batch will have this number of entities to be created as a batch

    // total data size can be calculated 
    // total_size = batch_amount * batch_size * object_size
    // the  total size can be tuned with changing any parameter listed above.

    var batch = list<struct<product>>();
    for (x in range(batch_amount)) {
        val shift_index = x * batch_size;
        for (y in range(batch_size)) {
            batch.add(
                struct<product>(
                    name = name + shift_index + y,
                    description = description,
                    quantity = shift_index + y,
                    price = shift_index + y
                )
            );
        }
        create product ( batch );
        batch.clear();
        print("saved", x);      
    }
}

The [Query](https://docs.chromia.com/rell/core-concepts#queries) named get_products_paginated retrieves paginated products from the node. The pagination is based on the cursor implemented in the FT4 library.

./main.rell
 query get_products_paginated(page_size: integer?, page_cursor: text?): paginator.paged_result {
    val before_rowid = paginator.before_rowid(page_cursor);

    val paginated_result = product @* {
        .rowid > (before_rowid ?: rowid(0))
    } (
        paginator.pagination_result(
            data = map_product($).to_gtv_pretty(),
            rowid = .rowid
        )
    ) limit paginator.fetch_data_size(page_size);

    return paginator.make_page(paginated_result, page_size);
}

Data Modelling

product {
    name: text;
    description: text;
    quantity: integer;
    price: integer;
}