> For the complete documentation index, see [llms.txt](https://docs.vexanium.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.vexanium.com/getting-started/smart-contract-development/secondary-indices.md). # Secondary Indices VEXANIUM has the ability to sort tables by up to 16 indices. In the following section, we're going to add another index to the `addressbook` contract, so we can iterate through the records in a different way. ### Step 1: Remove existing data from table[](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/secondary-indices#step-1-remove-existing-data-from-table) As mentioned earlier, *a table's struct cannot be modified when it contains data.* This first step allows the removal of the data already added. Remove all records of alice and bob that were added in previous tutorial. ``` cleos push action addressbook erase '["alice"]' -p alice@active ``` ``` cleos push action addressbook erase '["bob"]' -p bob@active ``` ### Step 2: Add new index member and getter[](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/secondary-indices#step-2-add-new-index-member-and-getter) Add a new member variable and its getter to the `addressbook.cpp` contract. Since the secondary index needs to be numeric field, a `uint64_t` age variable is added. ```cpp uint64_t age; uint64_t get_secondary_1() const { return age;} ``` ### Step 3: Add secondary index to `addresses` table configuration[](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/secondary-indices#step-3-add-secondary-index-to-addresses-table-configuration) A field has been defined as the secondary index, next the `address_index` table needs to be reconfigured. ```cpp using address_index = eosio::multi_index<"people"_n, person, indexed_by<"byage"_n, const_mem_fun> >; ``` In the third parameter, we pass a `indexed_by` struct which is used to instantiate a index. In that `indexed_by` struct, we specify the name of index as `"byage"` and the second type parameter as a function call operator which extracts a const value as an index key. In this case, we point it to the getter we created earlier so this multiple index table will index records by the `age` variable. ``` indexed_by<"byage"_n, const_mem_fun> ``` ### Step 4: Modify code[](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/secondary-indices#step-4-modify-code) With all the changes in previous steps, we can now update the `upsert` function. Change the function parameter list to the following: ```cpp void upsert(name user, std::string first_name, std::string last_name, uint64_t age, std::string street, std::string city, std::string state) ``` Add additional lines to update `age` field in `upsert` function as the following: ```cpp void upsert(name user, std::string first_name, std::string last_name, uint64_t age, std::string street, std::string city, std::string state) { require_auth( user ); address_index addresses( get_first_receiver(), get_first_receiver().value); auto iterator = addresses.find(user.value); if( iterator == addresses.end() ) { addresses.emplace(user, [&]( auto& row ) { row.key = user; row.first_name = first_name; row.last_name = last_name; // -- Add code below -- row.age = age; row.street = street; row.city = city; row.state = state; }); } else { addresses.modify(iterator, user, [&]( auto& row ) { row.key = user; row.first_name = first_name; row.last_name = last_name; // -- Add code below -- row.age = age; row.street = street; row.city = city; row.state = state; }); } } ``` ### Step 5: Compile and Deploy[](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/secondary-indices#step-5-compile-and-deploy) Compile ``` eosio-cpp --abigen addressbook.cpp -o addressbook.wasm ``` Deploy ```sh cleos set contract addressbook CONTRACTS_DIR/addressbook ``` ### Step 6: Test it[](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/secondary-indices#step-6-test-it) Insert records ``` cleos push action addressbook upsert '["alice", "alice", "liddell", 9, "123 drink me way", "wonderland", "amsterdam"]' -p alice@active ``` ``` cleos push action addressbook upsert '["bob", "bob", "is a guy", 49, "doesnt exist", "somewhere", "someplace"]' -p bob@active ``` Look up alice's address by the age index. Here the `--index 2` parameter is used to indicate that the query applies to the secondary index ``` cleos get table addressbook addressbook people --upper 10 \ --key-type i64 \ --index 2 ``` You should see something like the following ``` { "rows": [{ "key": "alice", "first_name": "alice", "last_name": "liddell", "age": 9, "street": "123 drink me way", "city": "wonderland", "state": "amsterdam" } ], "more": false, "next_key": "" } ``` Look it up by Bob's age ``` cleos get table addressbook addressbook people --upper 50 --key-type i64 --index 2 ``` It should return ``` { "rows": [{ "key": "alice", "first_name": "alice", "last_name": "liddell", "age": 9, "street": "123 drink me way", "city": "wonderland", "state": "amsterdam" },{ "key": "bob", "first_name": "bob", "last_name": "is a guy", "age": 49, "street": "doesnt exist", "city": "somewhere", "state": "someplace" } ], "more": false } ``` ### Wrapping Up[](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/secondary-indices#wrapping-up) The complete `addressbook` contract up to this point: ```cpp #include #include using namespace eosio; class [[eosio::contract("addressbook")]] addressbook : public eosio::contract { public: addressbook(name receiver, name code, datastream ds): contract(receiver, code, ds) {} [[eosio::action]] void upsert(name user, std::string first_name, std::string last_name, uint64_t age, std::string street, std::string city, std::string state) { require_auth( user ); address_index addresses(get_first_receiver(),get_first_receiver().value); auto iterator = addresses.find(user.value); if( iterator == addresses.end() ) { addresses.emplace(user, [&]( auto& row ) { row.key = user; row.first_name = first_name; row.last_name = last_name; row.age = age; row.street = street; row.city = city; row.state = state; }); } else { addresses.modify(iterator, user, [&]( auto& row ) { row.key = user; row.first_name = first_name; row.last_name = last_name; row.age = age; row.street = street; row.city = city; row.state = state; }); } } [[eosio::action]] void erase(name user) { require_auth(user); address_index addresses(get_self(), get_first_receiver().value); auto iterator = addresses.find(user.value); check(iterator != addresses.end(), "Record does not exist"); addresses.erase(iterator); } private: struct [[eosio::table]] person { name key; std::string first_name; std::string last_name; uint64_t age; std::string street; std::string city; std::string state; uint64_t primary_key() const { return key.value; } uint64_t get_secondary_1() const { return age; } }; using address_index = eosio::multi_index<"people"_n, person, indexed_by<"byage"_n, const_mem_fun>>; }; ``` ### What's Next?[](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/secondary-indices#whats-next) * [Adding Inline Actions](https://docs.eosnetwork.com/docs/latest/getting-started/smart-contract-development/adding-inline-actions): Learn how to construct actions and send those actions from within a contract.