How to get big map value on Babylon

Question

Babylon will have a new RPC to query big map value according to this link http://tezos.gitlab.io/babylonnet/api/rpc.html#get-block-id-context-big-maps-big-map-id-script-expr

I tried using it with a new contract. I deployed this contract https://babylonnet.tzscan.io/KT1DT9YwHdSbZuVuZDjd1SMUcfXm57R5bE9v

If I understood correctly, the id of my big map should be 22

Knowing that my big map got initialized with a key tz1bwsEWCwSEXdRvnJxvegQZKeX5dj6oKEys

What is the correct way to get the value using either the cli or rpc?

I have tried:

tezos get element tz1bwsEWCwSEXdRvnJxvegQZKeX5dj6oKEys of big map 22

http://babylonnet-node.tzscan.io/chains/main/blocks/head/context/big_maps/22/tz1bwsEWCwSEXdRvnJxvegQZKeX5dj6oKEys

Both do not work. If I understand correctly, I will probably need to encode my key. I am unsure about what the required encoding is and can't seem to find an example that works.

Answer 1

The new CLI and RPC for big map expect hash of a script expression, instead of the raw expression. To obtain the hash you can e.g.:

tezos-client hash data '"tz1bwsEWCwSEXdRvnJxvegQZKeX5dj6oKEys"' of type address

This will print hashes in bunch of different formats - you want the one with the label Script-expression-ID-Hash, e.g. exprv6UsC1sN3Fk2XfgcJCL8NCerP5rCGy1PRESZAqr7L2JdzX55EN.

Then you can use this with the CLI:

tezos-client get element exprv6UsC1sN3Fk2XfgcJCL8NCerP5rCGy1PRESZAqr7L2JdzX55EN of big map 22

and RPC at:

/chains/main/blocks/head/context/big_maps/22/exprv6UsC1sN3Fk2XfgcJCL8NCerP5rCGy1PRESZAqr7L2JdzX55EN

Edit:

A new CLI command has been added for simpler big map access:

tezos-client get big map value for '"tz1bwsEWCwSEXdRvnJxvegQZKeX5dj6oKEys"' of type address in <src>

where <src> can be an alias, a key, or a literal (in your case KT1DT9YwHdSbZuVuZDjd1SMUcfXm57R5bE9v).

Answer 2

The cli command is tezos-client get big map value for <key> of type <type of the key> in <contract>. By adding the -l option, we also get the RPC: /chains/main/blocks/head/context/contracts/<contract address>/big_map_get.

Actually, you do not need to know the big map index, if several big_maps with the same type of keys are stored, they will all be searched for the key.