![\"\"](\"https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2021\/09\/Screen-Shot-2021-09-07-at-10.34.28-am-1024x338.png\")
<\/figure>\n\n\n\n<\/p>\n\n\n\n
Pre-requisites <\/h1>\n\n\n\n
Have gone through the SubQuery Hello World<\/a> exercise. This ensures your environment has all the required applications.<\/p>\n\n\n\n This will set up the scaffolding making everything a lot easier.<\/p>\n\n\n\n The first step is to create your schema file which “defines the shape of your data”. Here we will define 2 entities or objects, Account and Transfer.<\/p>\n\n\n\n In the manifest file, we want to create a handler called handleTransfer (to be written next). This is a standard substrate\/Eventhandler and we will filter on the balances module. The filter is optional but recommended as they significantly reduce the amount of data processed by your SubQuery project and will improve indexing performance. <\/p>\n\n\n\n This is perhaps the most challenging part for those still learning SubQuery and Polkdadot. What the code below does is create a helper function called “ensureAccounts” and a handleTransfer EventHandler function to grab the transferred amount along with the to and from Id. <\/p>\n\n\n\n Run the standard commands.<\/p>\n\n\n\n <\/p>\n\n\n\n Now comes the fun part, the query. Below is an example query that can be used. <\/p>\n\n\n\n This will return:<\/p>\n\n\n\n And this matches subscan<\/a>.<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" Introduction What we will do here is to write a<\/p>\n","protected":false},"author":1,"featured_media":3405,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-3115","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blockchain"],"featured_image_urls":{"full":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses.png",1538,910,false],"thumbnail":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses-150x150.png",150,150,true],"medium":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses-300x178.png",300,178,true],"medium_large":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses-768x454.png",640,378,true],"large":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses-1024x606.png",640,379,true],"1536x1536":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses-1536x909.png",1536,909,true],"2048x2048":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses.png",1538,910,false],"chromenews-featured":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses-1024x606.png",1024,606,true],"chromenews-large":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses-825x575.png",825,575,true],"chromenews-medium":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2023\/11\/addresses-590x410.png",590,410,true]},"author_info":{"info":["seandotau"]},"category_info":"Blockchain<\/a>","tag_info":"Blockchain","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/posts\/3115","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/comments?post=3115"}],"version-history":[{"count":1,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/posts\/3115\/revisions"}],"predecessor-version":[{"id":3122,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/posts\/3115\/revisions\/3122"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/media\/3405"}],"wp:attachment":[{"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/media?parent=3115"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/categories?post=3115"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/tags?post=3115"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Step 1: Run subql init<\/h1>\n\n\n\n
~\/Code\/subQuery\/projects$ subql init\nProject name [subql-starter]: subql-list-transactions\nGit repository: \nRPC endpoint [wss:\/\/polkadot.api.onfinality.io\/public-ws]: \nAuthors: sa\nDescription: \nVersion: [1.0.0]: \nLicense: [Apache-2.0]: \nInit the starter package... subql-list-transactions is ready\n~\/Code\/subQuery\/projects$ <\/code><\/pre>\n\n\n\nStep 2: Create a schema<\/h1>\n\n\n\n
type Account @entity {\n id: ID!\n sentTransfers: [Transfer] @derivedFrom(field: \"from\")\n receivedTransfers: [Transfer] @derivedFrom(field: \"to\")\n}\n\ntype Transfer @entity {\n id: ID!\n amount: BigInt\n to: Account!\n from: Account!\n}<\/code><\/pre>\n\n\n\nStep 3: Update the manifest file<\/h1>\n\n\n\n
specVersion: 0.0.1\ndescription: \"\"\nrepository: \"\"\nschema: .\/schema.graphql\nnetwork:\n endpoint: wss:\/\/polkadot.api.onfinality.io\/public-ws\ndataSources:\n - name: main\n kind: substrate\/Runtime\n startBlock: 6716560\n mapping:\n handlers:\n - handler: handleTransfer\n kind: substrate\/EventHandler\n filter:\n module: balances\n method: Transfer\n<\/code><\/pre>\n\n\n\nStep 4: Writing the mappings<\/h1>\n\n\n\n
import {SubstrateExtrinsic,SubstrateEvent,SubstrateBlock} from \"@subql\/types\";\nimport {Transfer, Account} from \"..\/types\";\nimport {Balance} from \"@polkadot\/types\/interfaces\";\n\nasync function ensureAccounts(accountIds: string[]): Promise<void> {\n for (const accountId of accountIds) {\n const account = await Account.get(accountId);\n if (!account) {\n await new Account(accountId).save();\n }\n }\n}\n\nexport async function handleTransfer(event: SubstrateEvent): Promise<void> {\n const {\n event: {\n data: [from, to, amount],\n },\n } = event;\n await ensureAccounts([from.toString(), to.toString()]);\n const transferInfo = new Transfer(\n `${event.block.block.header.number.toNumber()}-${event.idx}`,\n );\n transferInfo.fromId = from.toString();\n transferInfo.toId = to.toString();\n transferInfo.amount = (amount as Balance).toBigInt();\n await transferInfo.save();\n}\n<\/code><\/pre>\n\n\n\nStep 5: Build and deploy<\/h1>\n\n\n\n
yarn codegen\nyarn build\ndocker-compose pull & docker-compose up<\/code><\/pre>\n\n\n\nStep 6: Query<\/h1>\n\n\n\n
query {\n accounts (first:15 orderBy:CREATED_AT_DESC filter:{id: {equalTo: \"12qvDzHzs3LFBnir7UAYR154t4ZWNLjMehniqLhTp2CBCeW4\"}} ) {\n nodes {\n id\n createdAt\n updatedAt\n recievedTransfers {\n edges {\n node {\n id\n amount\n }\n }\n }\n }\n }\n transfers ( orderBy:CREATED_AT_DESC filter:{id: {equalTo: \"12qvDzHzs3LFBnir7UAYR154t4ZWNLjMehniqLhTp2CBCeW4\"}} ) {\n nodes {\n id\n createdAt\n updatedAt\n amount\n toId\n fromId\n }\n }\n}<\/code><\/pre>\n\n\n\n{\n \"data\": {\n \"accounts\": {\n \"nodes\": [\n {\n \"id\": \"12qvDzHzs3LFBnir7UAYR154t4ZWNLjMehniqLhTp2CBCeW4\",\n \"createdAt\": \"2021-09-07T00:01:15.719+00:00\",\n \"updatedAt\": \"2021-09-07T00:01:15.719+00:00\",\n \"recievedTransfers\": {\n \"edges\": [\n {\n \"node\": {\n \"id\": \"6716562-3\",\n \"amount\": \"20000000000\"\n }\n },\n {\n \"node\": {\n \"id\": \"6716591-1\",\n \"amount\": \"700000000000\"\n }\n }\n ]\n }\n }\n ]\n },\n \"transfers\": {\n \"nodes\": []\n }\n }\n}<\/code><\/pre>\n\n\n\n![\"\"](\"https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2021\/09\/image-1024x478.png\")
<\/figure>\n\n\n\n