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Composite queries

View this sample's code on GitHub

Building the example​

We first need to build the data partition backend canister.

git clone https://github.com/dfinity/examples
cd examples/rust/composite_query
dfx start --background
dfx canister create data_partition
dfx build data_partition

During the compilation of the fronted canister, the canister's wasm code will be inlined in the frontend canister's wasm code.

dfx canister create kv_frontend
dfx build kv_frontend
dfx canister install kv_frontend

Using the canister​

Now we add some key value pairs via the frontend canister.

dfx canister call kv_frontend put '(1:nat, 1337:nat)'
(null)
dfx canister call kv_frontend put '(1:nat, 42:nat)'
(opt (1_337 : nat))

Note that the first call to put is slow, since the data partitions have to be created first.

dfx canister call kv_frontend get '(1:nat)'
(opt (42 : nat))

We can also query it via a (duplicate) method by doing update calls:

dfx canister call kv_frontend get_update '(1:nat)'
(opt (1_337 : nat))

It's also possible to do two query calls, first into the frontend and then into the data partition:

$ dfx canister call kv_frontend lookup '(1: nat)'
(1 : nat, "dmalx-m4aaa-aaaaa-qaanq-cai")
$ dfx canister call dmalx-m4aaa-aaaaa-qaanq-cai get '(1: nat)' --query
(1_337 : nat)