Generate GQL API for subgraph entities and auto-diff based on store set (#38)

* Add subgraph schema types to the generated schema

* Add queries for subgraph entities

* Add entity generation for subgraph entities

* Call subgraph event handler in indexer

* Refactor subgraph schema and entity generation

* Add resolvers generation for subgraph entities

* Get event signature in the event

* Add NonNullType check for field type in entity generation

* Auto-diff based on store set

* Use contract address from data source in loader

* Change subgraph-schema arg to subgraph-path arg

packages/codegen/README.md

@@ -21,7 +21,7 @@
 * Run the following command to generate a watcher from a contract file:
 
   ```bash
-  yarn codegen --input-file <input-file-path> --contract-name <contract-name> --output-folder [output-folder] --mode [eth_call | storage | all] --flatten [true | false] --kind [lazy | active] --port [server-port]
+  yarn codegen --input-file <input-file-path> --contract-name <contract-name> --output-folder [output-folder] --mode [eth_call | storage | all] --flatten [true | false] --kind [lazy | active] --port [server-port] --subgraph-path [subgraph-build-path]
   ```
 
     * `input-file`(alias: `i`): Input contract file path or an URL (required).
@@ -31,6 +31,7 @@
     * `flatten`(alias: `f`): Flatten the input contract file (default: `true`).
     * `kind` (alias: `k`): Kind of watcher (default: `active`).
     * `port` (alias: `p`): Server port (default: `3008`).
+    * `subgraph-path` (alias: `s`): Path to the subgraph build.
 
   **Note**: When passed an *URL* as `input-file`, it is assumed that it points to an already flattened contract file.
 
@@ -78,12 +79,14 @@
   ipfs daemon
   ```
 
-* Create the databases configured in `environments/local.toml`.
+* In the config file (`environments/local.toml`):
 
-* Update the state checkpoint settings in `environments/local.toml`.
+  * Update the state checkpoint settings.
 
   * Update the IPFS API address in `environments/local.toml`.
 
+* Create the databases configured in `environments/local.toml`.
+
 ### Customize
 
 * Indexing on an event:

packages/codegen/package.json

@@ -19,6 +19,7 @@
   },
   "homepage": "https://github.com/vulcanize/watcher-ts#readme",
   "dependencies": {
+    "@graphql-tools/load-files": "^6.5.2",
     "@poanet/solidity-flattener": "https://github.com/vulcanize/solidity-flattener.git",
     "@solidity-parser/parser": "^0.13.2",
     "@vulcanize/util": "^0.1.0",

packages/codegen/src/config.ts

@@ -16,13 +16,14 @@ const TEMPLATE_FILE = './templates/config-template.handlebars';
  * @param folderName Watcher folder name to be passed to the template.
  * @param outStream A writable output stream to write the config file to.
  */
-export function exportConfig (watcherKind: string, port: number, folderName: string, outStream: Writable): void {
+export function exportConfig (watcherKind: string, port: number, folderName: string, outStream: Writable, subgraphPath?: string): void {
   const templateString = fs.readFileSync(path.resolve(__dirname, TEMPLATE_FILE)).toString();
   const template = Handlebars.compile(templateString);
   const config = template({
     watcherKind,
     port,
-    folderName
+    folderName,
+    subgraphPath
   });
   outStream.write(config);
 }

packages/codegen/src/data/entities/BlockProgress.yaml

@@ -9,6 +9,9 @@ indexOn:
   - columns:
       - parentHash
 columns:
+  - name: id
+    tsType: number
+    columnType: PrimaryGeneratedColumn
   - name: cid
     pgType: varchar
     tsType: string

packages/codegen/src/data/entities/Contract.yaml

@@ -4,6 +4,9 @@ indexOn:
       - address
     unique: true
 columns:
+  - name: id
+    tsType: number
+    columnType: PrimaryGeneratedColumn
   - name: address
     pgType: varchar
     tsType: string

packages/codegen/src/data/entities/Event.yaml

@@ -8,6 +8,9 @@ indexOn:
       - contract
       - eventName
 columns:
+  - name: id
+    tsType: number
+    columnType: PrimaryGeneratedColumn
   - name: block
     tsType: BlockProgress
     columnType: ManyToOne

packages/codegen/src/data/entities/HookStatus.yaml

@@ -1,6 +1,9 @@
 className: HookStatus
 indexOn: []
 columns:
+  - name: id
+    tsType: number
+    columnType: PrimaryGeneratedColumn
   - name: latestProcessedBlockNumber
     pgType: integer
     tsType: number

packages/codegen/src/data/entities/IPLDBlock.yaml

@@ -12,6 +12,9 @@ indexOn:
       - kind
     unique: true
 columns:
+  - name: id
+    tsType: number
+    columnType: PrimaryGeneratedColumn
   - name: block
     tsType: BlockProgress
     columnType: ManyToOne

packages/codegen/src/data/entities/SyncStatus.yaml

@@ -2,6 +2,9 @@ className: SyncStatus
 implements: SyncStatusInterface
 indexOn: []
 columns:
+  - name: id
+    tsType: number
+    columnType: PrimaryGeneratedColumn
   - name: chainHeadBlockHash
     pgType: varchar
     tsType: string

packages/codegen/src/entity.ts

@@ -9,7 +9,7 @@ import yaml from 'js-yaml';
 import Handlebars from 'handlebars';
 import { Writable } from 'stream';
 
-import { getTsForSol, getPgForTs } from './utils/type-mappings';
+import { getTsForSol, getPgForTs, getTsForGql } from './utils/type-mappings';
 import { Param } from './utils/types';
 
 const TEMPLATE_FILE = './templates/entity-template.handlebars';
@@ -67,6 +67,12 @@ export class Entity {
     );
     entityObject.indexOn.push(indexObject);
 
+    entityObject.columns.push({
+      name: 'id',
+      tsType: 'number',
+      columnType: 'PrimaryGeneratedColumn',
+      columnOptions: []
+    });
     entityObject.columns.push({
       name: 'blockHash',
       pgType: 'varchar',
@@ -156,30 +162,8 @@ export class Entity {
       ]
     });
 
-    entityObject.columns.forEach((column: any) => {
-      if (column.tsType === 'bigint') {
-        column.columnOptions.push(
-          {
-            option: 'transformer',
-            value: 'bigintTransformer'
-          }
-        );
-        const importObject = entityObject.imports.find((element: any) => {
-          return element.from === '@vulcanize/util';
-        });
-
-        if (importObject) {
-          importObject.toImport.add('bigintTransformer');
-        } else {
-          entityObject.imports.push(
-            {
-              toImport: new Set(['bigintTransformer']),
-              from: '@vulcanize/util'
-            }
-          );
-        }
-      }
-    });
+    // Add bigintTransformer column option if required.
+    this._addBigIntTransformerOption(entityObject);
 
     this._entities.push(entityObject);
   }
@@ -206,6 +190,66 @@ export class Entity {
     });
   }
 
+  addSubgraphEntities (subgraphSchemaDocument: any): void {
+    const subgraphTypeDefs = subgraphSchemaDocument.definitions;
+
+    subgraphTypeDefs.forEach((def: any) => {
+      // TODO Handle enum types.
+      if (def.kind !== 'ObjectTypeDefinition') {
+        return;
+      }
+
+      let entityObject: any = {
+        className: def.name.value,
+        indexOn: [],
+        columns: [],
+        imports: []
+      };
+
+      entityObject.imports.push(
+        {
+          toImport: new Set(['Entity', 'PrimaryColumn', 'Column']),
+          from: 'typeorm'
+        }
+      );
+
+      // Add common columns.
+      entityObject.columns.push({
+        name: 'id',
+        pgType: 'varchar',
+        tsType: 'string',
+        columnType: 'PrimaryColumn',
+        columnOptions: []
+      });
+      entityObject.columns.push({
+        name: 'blockHash',
+        pgType: 'varchar',
+        tsType: 'string',
+        columnType: 'PrimaryColumn',
+        columnOptions: [
+          {
+            option: 'length',
+            value: 66
+          }
+        ]
+      });
+      entityObject.columns.push({
+        name: 'blockNumber',
+        pgType: 'integer',
+        tsType: 'number',
+        columnType: 'Column'
+      });
+
+      // Add subgraph entity specific columns.
+      entityObject = this._addSubgraphColumns(entityObject, def);
+
+      // Add bigintTransformer column option if required.
+      this._addBigIntTransformerOption(entityObject);
+
+      this._entities.push(entityObject);
+    });
+  }
+
   _addEventEntity (): void {
     const entity = yaml.load(fs.readFileSync(path.resolve(__dirname, TABLES_DIR, 'Event.yaml'), 'utf8'));
     this._entities.push(entity);
@@ -235,4 +279,123 @@ export class Entity {
     const entity = yaml.load(fs.readFileSync(path.resolve(__dirname, TABLES_DIR, 'HookStatus.yaml'), 'utf8'));
     this._entities.push(entity);
   }
+
+  _addBigIntTransformerOption (entityObject: any): void {
+    entityObject.columns.forEach((column: any) => {
+      if (column.tsType === 'bigint') {
+        column.columnOptions.push(
+          {
+            option: 'transformer',
+            value: 'bigintTransformer'
+          }
+        );
+
+        const importObject = entityObject.imports.find((element: any) => {
+          return element.from === '@vulcanize/util';
+        });
+
+        if (importObject) {
+          importObject.toImport.add('bigintTransformer');
+        } else {
+          entityObject.imports.push(
+            {
+              toImport: new Set(['bigintTransformer']),
+              from: '@vulcanize/util'
+            }
+          );
+        }
+      }
+    });
+  }
+
+  _addSubgraphColumns (entityObject: any, def: any): any {
+    def.fields.forEach((field: any) => {
+      const name = field.name.value;
+
+      // Filter out already added columns.
+      if (['id', 'blockHash', 'blockNumber'].includes(name)) {
+        return;
+      }
+
+      const columnObject: any = {
+        name,
+        columnOptions: []
+      };
+
+      const { typeName, array, nullable } = this._getFieldType(field.type);
+      let tsType = getTsForGql(typeName);
+
+      if (tsType) {
+        // Handle basic array types.
+        if (array) {
+          columnObject.columnOptions.push({
+            option: 'array',
+            value: 'true'
+          });
+
+          columnObject.tsType = `${tsType}[]`;
+        } else {
+          columnObject.tsType = tsType;
+        }
+      } else {
+        // TODO Handle array of custom types.
+        tsType = typeName;
+        columnObject.tsType = tsType;
+      }
+
+      const pgType = getPgForTs(tsType);
+
+      // If basic type: create a column. If unknown: create a relation.
+      if (pgType) {
+        columnObject.columnType = 'Column';
+        columnObject.pgType = pgType;
+      } else {
+        columnObject.columnType = 'ManyToOne';
+        columnObject.lhs = '()';
+        columnObject.rhs = tsType;
+
+        entityObject.imports[0].toImport.add('ManyToOne');
+
+        // Check if type import already added.
+        const importObject = entityObject.imports.find((element: any) => {
+          return element.from === `./${tsType}`;
+        });
+
+        if (!importObject) {
+          entityObject.imports.push(
+            {
+              toImport: new Set([tsType]),
+              from: `./${tsType}`
+            }
+          );
+        }
+      }
+
+      if (nullable) {
+        columnObject.columnOptions.push({
+          option: 'nullable',
+          value: 'true'
+        });
+      }
+
+      entityObject.columns.push(columnObject);
+    });
+
+    return entityObject;
+  }
+
+  _getFieldType (typeNode: any): { typeName: string, array: boolean, nullable: boolean } {
+    if (typeNode.kind === 'ListType') {
+      return { typeName: this._getFieldType(typeNode.type).typeName, array: true, nullable: true };
+    }
+
+    if (typeNode.kind === 'NonNullType') {
+      const fieldType = this._getFieldType(typeNode.type);
+
+      return { typeName: fieldType.typeName, array: fieldType.array, nullable: false };
+    }
+
+    // If 'NamedType'.
+    return { typeName: typeNode.name.value, array: false, nullable: true };
+  }
 }

packages/codegen/src/generate-code.ts

@@ -78,6 +78,11 @@ const main = async (): Promise<void> => {
       type: 'boolean',
       default: true
     })
+    .option('subgraph-path', {
+      alias: 's',
+      describe: 'Path to the subgraph build.',
+      type: 'string'
+    })
     .argv;
 
   let data: string;
@@ -144,6 +149,8 @@ function generateWatcher (data: string, visitor: Visitor, argv: any) {
 
   registerHandlebarHelpers();
 
+  visitor.visitSubgraph(argv['subgraph-path']);
+
   let outStream = outputDir
     ? fs.createWriteStream(path.join(outputDir, 'src/schema.gql'))
     : process.stdout;
@@ -167,7 +174,7 @@ function generateWatcher (data: string, visitor: Visitor, argv: any) {
   outStream = outputDir
     ? fs.createWriteStream(path.join(outputDir, 'environments/local.toml'))
     : process.stdout;
-  exportConfig(argv.kind, argv.port, path.basename(outputDir), outStream);
+  exportConfig(argv.kind, argv.port, path.basename(outputDir), outStream, argv['subgraph-path']);
 
   outStream = outputDir
     ? fs.createWriteStream(path.join(outputDir, 'src/artifacts/', `${inputFileName}.json`))

packages/codegen/src/resolvers.ts

@@ -16,10 +16,12 @@ const TEMPLATE_FILE = './templates/resolvers-template.handlebars';
 
 export class Resolvers {
   _queries: Array<any>;
+  _subgraphQueries: Array<any>;
   _templateString: string;
 
   constructor () {
     this._queries = [];
+    this._subgraphQueries = [];
     this._templateString = fs.readFileSync(path.resolve(__dirname, TEMPLATE_FILE)).toString();
   }
 
@@ -51,6 +53,26 @@ export class Resolvers {
     this._queries.push(queryObject);
   }
 
+  addSubgraphResolvers (subgraphSchemaDocument: any): void {
+    const subgraphTypeDefs = subgraphSchemaDocument.definitions;
+
+    for (const subgraphTypeDef of subgraphTypeDefs) {
+      if (subgraphTypeDef.kind !== 'ObjectTypeDefinition') {
+        continue;
+      }
+
+      const entityName = subgraphTypeDef.name.value;
+      const queryName = `${entityName.charAt(0).toLowerCase()}${entityName.slice(1)}`;
+
+      const queryObject = {
+        entityName,
+        queryName
+      };
+
+      this._subgraphQueries.push(queryObject);
+    }
+  }
+
   /**
    * Writes the resolvers file generated from a template to a stream.
    * @param outStream A writable output stream to write the resolvers file to.
@@ -58,7 +80,8 @@ export class Resolvers {
   exportResolvers (outStream: Writable): void {
     const template = Handlebars.compile(this._templateString);
     const obj = {
-      queries: this._queries
+      queries: this._queries,
+      subgraphQueries: this._subgraphQueries
     };
     const resolvers = template(obj);
     outStream.write(resolvers);

packages/codegen/src/schema.ts

@@ -3,9 +3,10 @@
 //
 
 import assert from 'assert';
-import { GraphQLSchema, printSchema } from 'graphql';
+import { GraphQLSchema, parse, printSchema, print } from 'graphql';
 import { SchemaComposer } from 'graphql-compose';
 import { Writable } from 'stream';
+import _ from 'lodash';
 
 import { getTsForSol, getGqlForTs } from './utils/type-mappings';
 import { Param } from './utils/types';
@@ -28,6 +29,11 @@ export class Schema {
    * @param returnType Return type for the query.
    */
   addQuery (name: string, params: Array<Param>, returnType: string): void {
+    // Check if the query is already added.
+    if (this._composer.Query.hasField(name)) {
+      return;
+    }
+
     // TODO: Handle cases where returnType/params type is an array.
     const tsReturnType = getTsForSol(returnType);
     assert(tsReturnType);
@@ -63,6 +69,11 @@ export class Schema {
   addEventType (name: string, params: Array<Param>): void {
     name = `${name}Event`;
 
+    // Check if the type is already added.
+    if (this._composer.has(name)) {
+      return;
+    }
+
     const typeObject: any = {};
     typeObject.name = name;
     typeObject.fields = {};
@@ -97,15 +108,18 @@ export class Schema {
     // Add a mutation for watching a contract.
     this._addWatchContractMutation();
 
+    // Add IPLDBlock type and queries.
     this._addIPLDType();
     this._addIPLDQuery();
 
+    // Build the schema.
     return this._composer.buildSchema();
   }
 
   /**
    * Writes schema to a stream.
    * @param outStream A writable output stream to write the schema to.
+   * @returns The schema string.
    */
   exportSchema (outStream: Writable): string {
     // Get schema as a string from GraphQLSchema.
@@ -115,48 +129,112 @@ export class Schema {
     return schemaString;
   }
 
+  addSubgraphSchema (subgraphSchemaDocument: any): void {
+    // Generating the current types.
+    const schema = this._composer.buildSchema();
+
+    const schemaString = printSchema(schema);
+
+    // Parse the schema into a DocumentNode.
+    const schemaDocument = parse(schemaString);
+
+    // Get schema types.
+    const schemaTypes = schemaDocument.definitions.map((def: any) => {
+      return def.name.value;
+    });
+
+    // Filtering out existing types from subgraph types.
+    const subgraphTypeDefs = subgraphSchemaDocument.definitions.filter((def: any) => {
+      return !schemaTypes.includes(def.name.value);
+    });
+
+    // Re-assigning the typeDefs.
+    const modifiedSchemaDocument = _.cloneDeep(subgraphSchemaDocument);
+    modifiedSchemaDocument.definitions = subgraphTypeDefs;
+
+    // Adding subgraph-schema types to the schema composer.
+    const subgraphTypeDefsString = print(modifiedSchemaDocument);
+    this._composer.addTypeDefs(subgraphTypeDefsString);
+
+    // Add subgraph-schema entity queries to the schema composer.
+    this._addSubgraphSchemaQueries(subgraphTypeDefs);
+  }
+
+  _addSubgraphSchemaQueries (subgraphTypeDefs: any): void {
+    for (const subgraphTypeDef of subgraphTypeDefs) {
+      // Filtering out enums.
+      if (subgraphTypeDef.kind !== 'ObjectTypeDefinition') {
+        continue;
+      }
+
+      const subgraphType = subgraphTypeDef.name.value;
+
+      // Lowercase first letter for query name.
+      const queryName = `${subgraphType.charAt(0).toLowerCase()}${subgraphType.slice(1)}`;
+
+      const queryObject: { [key: string]: any; } = {};
+      queryObject[queryName] = {
+        // Get type composer object for return type from the schema composer.
+        type: this._composer.getAnyTC(subgraphType).NonNull,
+        args: {
+          id: 'String!',
+          blockHash: 'String!'
+        }
+      };
+
+      this._composer.Query.addFields(queryObject);
+    }
+  }
+
   /**
    * Adds basic types to the schema and typemapping.
    */
   _addBasicTypes (): void {
+    let typeComposer;
+
     // Create a scalar type composer to add the scalar BigInt in the schema composer.
-    this._composer.createScalarTC({
+    typeComposer = this._composer.createScalarTC({
       name: 'BigInt'
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
 
     // Create a type composer to add the type Proof in the schema composer.
-    this._composer.createObjectTC({
+    typeComposer = this._composer.createObjectTC({
       name: 'Proof',
       fields: {
         data: 'String!'
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
 
-    this._composer.createObjectTC({
+    typeComposer = this._composer.createObjectTC({
       name: 'ResultBoolean',
       fields: {
         value: 'Boolean!',
         proof: () => this._composer.getOTC('Proof')
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
 
-    this._composer.createObjectTC({
+    typeComposer = this._composer.createObjectTC({
       name: 'ResultString',
       fields: {
         value: 'String!',
         proof: () => this._composer.getOTC('Proof')
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
 
-    this._composer.createObjectTC({
+    typeComposer = this._composer.createObjectTC({
       name: 'ResultInt',
       fields: {
         value: () => 'Int!',
         proof: () => this._composer.getOTC('Proof')
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
 
-    this._composer.createObjectTC({
+    typeComposer = this._composer.createObjectTC({
       name: 'ResultBigInt',
       fields: {
         // Get type composer object for BigInt scalar from the schema composer.
@@ -164,16 +242,19 @@ export class Schema {
         proof: () => this._composer.getOTC('Proof')
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
   }
 
   /**
    * Adds types 'ResultEvent' and 'WatchedEvent' to the schema.
    */
   _addEventsRelatedTypes (): void {
+    let typeComposer;
+
     // Create Ethereum types.
     // Create the Block type.
     const blockName = 'Block';
-    this._composer.createObjectTC({
+    typeComposer = this._composer.createObjectTC({
       name: blockName,
       fields: {
         cid: 'String!',
@@ -183,10 +264,11 @@ export class Schema {
         parentHash: 'String!'
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
 
     // Create the Transaction type.
     const transactionName = 'Transaction';
-    this._composer.createObjectTC({
+    typeComposer = this._composer.createObjectTC({
       name: transactionName,
       fields: {
         hash: 'String!',
@@ -195,10 +277,11 @@ export class Schema {
         to: 'String!'
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
 
     // Create the ResultEvent type.
     const resultEventName = 'ResultEvent';
-    this._composer.createObjectTC({
+    typeComposer = this._composer.createObjectTC({
       name: resultEventName,
       fields: {
         // Get type composer object for 'blockName' type from the schema composer.
@@ -210,6 +293,7 @@ export class Schema {
         proof: () => this._composer.getOTC('Proof')
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
   }
 
   /**
@@ -239,7 +323,7 @@ export class Schema {
   }
 
   _addIPLDType (): void {
-    this._composer.createObjectTC({
+    const typeComposer = this._composer.createObjectTC({
       name: 'ResultIPLDBlock',
       fields: {
         block: () => this._composer.getOTC('Block').NonNull,
@@ -249,6 +333,7 @@ export class Schema {
         data: 'String!'
       }
     });
+    this._composer.addSchemaMustHaveType(typeComposer);
   }
 
   _addIPLDQuery (): void {

packages/codegen/src/templates/checkpoint-template.handlebars

@@ -2,11 +2,13 @@
 // Copyright 2021 Vulcanize, Inc.
 //
 
+import path from 'path';
 import yargs from 'yargs';
 import 'reflect-metadata';
 import debug from 'debug';
 
 import { Config, DEFAULT_CONFIG_PATH, getConfig, initClients } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 
 import { Database } from '../database';
 import { Indexer } from '../indexer';
@@ -43,7 +45,16 @@ const main = async (): Promise<void> => {
   const db = new Database(config.database);
   await db.init();
 
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
+
   const blockHash = await indexer.processCLICheckpoint(argv.address, argv.blockHash);
 
   log(`Created a checkpoint for contract ${argv.address} at block-hash ${blockHash}`);

packages/codegen/src/templates/config-template.handlebars

@@ -12,6 +12,10 @@
   # IPFS API address (can be taken from the output on running the IPFS daemon).
   ipfsApiAddr = "/ip4/127.0.0.1/tcp/5001"
   
+  {{#if subgraphPath}}
+  subgraphPath = "{{subgraphPath}}"
+  {{/if}}
+
 [database]
   type = "postgres"
   host = "localhost"

packages/codegen/src/templates/entity-template.handlebars

@@ -17,14 +17,13 @@ import { {{~#each import.toImport}} {{this}} {{~#unless @last}}, {{~/unless}} {{
 {{/if}}
 {{/each}}
 export class {{className}} {{~#if implements}} implements {{implements}} {{~/if}} {
-  @PrimaryGeneratedColumn()
-  id!: number;
-
   {{#each columns as | column |}}
   {{#if (compare column.columnType 'ManyToOne')}}
   @{{column.columnType}}({{column.lhs}} => {{column.rhs}}
   {{~else}}
-  @{{column.columnType}}('{{column.pgType}}'
+  @{{column.columnType}}(
+  {{~#if column.pgType~}} '{{column.pgType}}'
+  {{~/if}}
   {{~/if}}
   {{~#if column.columnOptions}}, {
   {{~#each column.columnOptions}} {{this.option}}: {{{this.value}}}

packages/codegen/src/templates/export-state-template.handlebars

@@ -10,6 +10,7 @@ import fs from 'fs';
 import path from 'path';
 
 import { Config, DEFAULT_CONFIG_PATH, getConfig, initClients } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 import * as codec from '@ipld/dag-cbor';
 
 import { Database } from '../database';
@@ -42,7 +43,15 @@ const main = async (): Promise<void> => {
   const db = new Database(config.database);
   await db.init();
 
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
 
   const exportData: any = {
     snapshotBlock: {},

packages/codegen/src/templates/fill-template.handlebars

@@ -2,6 +2,7 @@
 // Copyright 2021 Vulcanize, Inc.
 //
 
+import path from 'path';
 import assert from 'assert';
 import 'reflect-metadata';
 import yargs from 'yargs';
@@ -10,6 +11,7 @@ import debug from 'debug';
 import { PubSub } from 'apollo-server-express';
 
 import { Config, getConfig, fillBlocks, JobQueue, DEFAULT_CONFIG_PATH, initClients } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 
 import { Database } from './database';
 import { Indexer } from './indexer';
@@ -46,10 +48,18 @@ export const main = async (): Promise<any> => {
   const db = new Database(config.database);
   await db.init();
 
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
   // Note: In-memory pubsub works fine for now, as each watcher is a single process anyway.
   // Later: https://www.apollographql.com/docs/apollo-server/data/subscriptions/#production-pubsub-libraries
   const pubsub = new PubSub();
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
 
   const jobQueueConfig = config.jobQueue;
   assert(jobQueueConfig, 'Missing job queue config');

packages/codegen/src/templates/import-state-template.handlebars

@@ -12,6 +12,7 @@ import fs from 'fs';
 import path from 'path';
 
 import { getConfig, fillBlocks, JobQueue, DEFAULT_CONFIG_PATH, Config, initClients } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 import * as codec from '@ipld/dag-cbor';
 
 import { Database } from '../database';
@@ -46,10 +47,18 @@ export const main = async (): Promise<any> => {
   const db = new Database(config.database);
   await db.init();
 
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
   // Note: In-memory pubsub works fine for now, as each watcher is a single process anyway.
   // Later: https://www.apollographql.com/docs/apollo-server/data/subscriptions/#production-pubsub-libraries
   const pubsub = new PubSub();
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
 
   const jobQueueConfig = config.jobQueue;
   assert(jobQueueConfig, 'Missing job queue config');

packages/codegen/src/templates/indexer-template.handlebars

@@ -17,6 +17,7 @@ import * as codec from '@ipld/dag-cbor';
 import { EthClient } from '@vulcanize/ipld-eth-client';
 import { StorageLayout } from '@vulcanize/solidity-mapper';
 import { Indexer as BaseIndexer, IndexerInterface, ValueResult, UNKNOWN_EVENT_NAME, ServerConfig, Where, QueryOptions, updateStateForElementaryType, updateStateForMappingType } from '@vulcanize/util';
+import { GraphWatcher } from '@vulcanize/graph-node';
 
 import { Database } from './database';
 import { Contract } from './entity/Contract';
@@ -53,6 +54,7 @@ export type ResultEvent = {
   contract: string;
 
   eventIndex: number;
+  eventSignature: string;
   event: any;
 
   proof: string;
@@ -79,6 +81,7 @@ export class Indexer implements IndexerInterface {
   _postgraphileClient: EthClient
   _baseIndexer: BaseIndexer
   _serverConfig: ServerConfig
+  _graphWatcher: GraphWatcher;
 
   _abi: JsonFragment[]
   _storageLayout: StorageLayout
@@ -86,7 +89,7 @@ export class Indexer implements IndexerInterface {
 
   _ipfsClient: IPFSClient
 
-  constructor (serverConfig: ServerConfig, db: Database, ethClient: EthClient, postgraphileClient: EthClient, ethProvider: BaseProvider) {
+  constructor (serverConfig: ServerConfig, db: Database, ethClient: EthClient, postgraphileClient: EthClient, ethProvider: BaseProvider, graphWatcher: GraphWatcher) {
     assert(db);
     assert(ethClient);
     assert(postgraphileClient);
@@ -97,6 +100,7 @@ export class Indexer implements IndexerInterface {
     this._ethProvider = ethProvider;
     this._serverConfig = serverConfig;
     this._baseIndexer = new BaseIndexer(this._db, this._ethClient, this._postgraphileClient, this._ethProvider);
+    this._graphWatcher = graphWatcher;
 
     const { abi, storageLayout } = artifacts;
 
@@ -114,7 +118,7 @@ export class Indexer implements IndexerInterface {
   getResultEvent (event: Event): ResultEvent {
     const block = event.block;
     const eventFields = JSONbig.parse(event.eventInfo);
-    const { tx } = JSON.parse(event.extraInfo);
+    const { tx, eventSignature } = JSON.parse(event.extraInfo);
 
     return {
       block: {
@@ -135,6 +139,7 @@ export class Indexer implements IndexerInterface {
       contract: event.contract,
 
       eventIndex: event.index,
+      eventSignature,
       event: {
         __typename: `${event.eventName}Event`,
         ...eventFields
@@ -552,9 +557,16 @@ export class Indexer implements IndexerInterface {
     return (ipfsAddr !== undefined && ipfsAddr !== null && ipfsAddr !== '');
   }
 
+  async getSubgraphEntity<Entity> (entity: new () => Entity, id: string, blockHash: string): Promise<Entity | undefined> {
+    return this._graphWatcher.getEntity(entity, id, blockHash);
+  }
+
   async triggerIndexingOnEvent (event: Event): Promise<void> {
     const resultEvent = this.getResultEvent(event);
 
+    // Call subgraph handler for event.
+    await this._graphWatcher.handleEvent(resultEvent);
+
     // Call custom hook function for indexing on event.
     await handleEvent(this, resultEvent);
   }
@@ -592,7 +604,11 @@ export class Indexer implements IndexerInterface {
       {{/each}}
     }
 
-    return { eventName, eventInfo };
+    return {
+      eventName,
+      eventInfo,
+      eventSignature: logDescription.signature
+    };
   }
 
   async watchContract (address: string, kind: string, checkpoint: boolean, startingBlock?: number): Promise<boolean> {
@@ -775,7 +791,7 @@ export class Indexer implements IndexerInterface {
         let eventName = UNKNOWN_EVENT_NAME;
         let eventInfo = {};
         const tx = transactionMap[txHash];
-        const extraInfo = { topics, data, tx };
+        const extraInfo: { [key: string]: any } = { topics, data, tx };
 
         const contract = ethers.utils.getAddress(address);
         const watchedContract = await this.isWatchedContract(contract);
@@ -784,6 +800,7 @@ export class Indexer implements IndexerInterface {
           const eventDetails = this.parseEventNameAndArgs(watchedContract.kind, logObj);
           eventName = eventDetails.eventName;
           eventInfo = eventDetails.eventInfo;
+          extraInfo.eventSignature = eventDetails.eventSignature;
         }
 
         dbEvents.push({

packages/codegen/src/templates/inspect-cid-template.handlebars

@@ -2,6 +2,7 @@
 // Copyright 2021 Vulcanize, Inc.
 //
 
+import path from 'path';
 import assert from 'assert';
 import yargs from 'yargs';
 import 'reflect-metadata';
@@ -9,6 +10,7 @@ import debug from 'debug';
 import util from 'util';
 
 import { Config, DEFAULT_CONFIG_PATH, getConfig, initClients } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 
 import { Database } from '../database';
 import { Indexer } from '../indexer';
@@ -41,7 +43,15 @@ const main = async (): Promise<void> => {
   const db = new Database(config.database);
   await db.init();
 
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
 
   const ipldBlock = await indexer.getIPLDBlockByCid(argv.cid);
   assert(ipldBlock, 'IPLDBlock for the provided CID doesn\'t exist.');

packages/codegen/src/templates/job-runner-template.handlebars

@@ -2,11 +2,13 @@
 // Copyright 2021 Vulcanize, Inc.
 //
 
+import path from 'path';
 import assert from 'assert';
 import 'reflect-metadata';
 import yargs from 'yargs';
 import { hideBin } from 'yargs/helpers';
 import debug from 'debug';
+
 import {
   getConfig,
   Config,
@@ -21,6 +23,7 @@ import {
   DEFAULT_CONFIG_PATH,
   initClients
 } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 
 import { Indexer } from './indexer';
 import { Database } from './database';
@@ -127,7 +130,15 @@ export const main = async (): Promise<any> => {
   const db = new Database(config.database);
   await db.init();
 
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
 
   const jobQueueConfig = config.jobQueue;
   assert(jobQueueConfig, 'Missing job queue config');

packages/codegen/src/templates/readme-template.handlebars

@@ -41,11 +41,13 @@
   {{folderName}}-job-queue=# exit
   ```
 
-* Update the [config](./environments/local.toml) with database connection settings.
+* In the [config file](./environments/local.toml):
 
-* Update the `upstream` config in the [config file](./environments/local.toml) and provide the `ipld-eth-server` GQL API and the `indexer-db` postgraphile endpoints.
+  * Update the database connection settings.
 
-* Update the `server` config in the [config file](./environments/local.toml) with state checkpoint settings and provide the IPFS API address.
+  * Update the `upstream` config and provide the `ipld-eth-server` GQL API and the `indexer-db` postgraphile endpoints.
+
+  * Update the `server` config with state checkpoint settings and provide the IPFS API address.
 
 ## Customize
 

packages/codegen/src/templates/reset-state-template.handlebars

@@ -2,11 +2,13 @@
 // Copyright 2021 Vulcanize, Inc.
 //
 
+import path from 'path';
 import debug from 'debug';
 import { MoreThan } from 'typeorm';
 import assert from 'assert';
 
 import { getConfig, initClients, resetJobs } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 
 import { Database } from '../../database';
 import { Indexer } from '../../indexer';
@@ -37,7 +39,15 @@ export const handler = async (argv: any): Promise<void> => {
   const db = new Database(config.database);
   await db.init();
 
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
 
   const syncStatus = await indexer.getSyncStatus();
   assert(syncStatus, 'Missing syncStatus');

packages/codegen/src/templates/resolvers-template.handlebars

@@ -11,6 +11,10 @@ import { ValueResult } from '@vulcanize/util';
 import { Indexer } from './indexer';
 import { EventWatcher } from './events';
 
+{{#each subgraphQueries as | query |}}
+import { {{query.entityName}} } from './entity/{{query.entityName}}';
+{{/each}}
+
 const log = debug('vulcanize:resolver');
 
 export const createResolvers = async (indexer: Indexer, eventWatcher: EventWatcher): Promise<any> => {
@@ -52,6 +56,15 @@ export const createResolvers = async (indexer: Indexer, eventWatcher: EventWatch
         {{~#each this.params}}, {{this.name~}} {{/each}});
       },
 
+      {{/each}}
+
+      {{~#each subgraphQueries}}
+      {{this.queryName}}: async (_: any, { id, blockHash }: { id: string, blockHash: string }): Promise<{{this.entityName}} | undefined> => {
+        log('{{this.queryName}}', id, blockHash);
+
+        return indexer.getSubgraphEntity({{this.entityName}}, id, blockHash);
+      },
+
       {{/each}}
       events: async (_: any, { blockHash, contractAddress, name }: { blockHash: string, contractAddress: string, name?: string }) => {
         log('events', blockHash, contractAddress, name);

packages/codegen/src/templates/server-template.handlebars

@@ -15,6 +15,7 @@ import 'graphql-import-node';
 import { createServer } from 'http';
 
 import { DEFAULT_CONFIG_PATH, getConfig, Config, JobQueue, KIND_ACTIVE, initClients } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 
 import { createResolvers } from './resolvers';
 import { Indexer } from './indexer';
@@ -42,10 +43,18 @@ export const main = async (): Promise<any> => {
   const db = new Database(config.database);
   await db.init();
 
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
   // Note: In-memory pubsub works fine for now, as each watcher is a single process anyway.
   // Later: https://www.apollographql.com/docs/apollo-server/data/subscriptions/#production-pubsub-libraries
   const pubsub = new PubSub();
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
 
   const jobQueueConfig = config.jobQueue;
   assert(jobQueueConfig, 'Missing job queue config');

packages/codegen/src/templates/watch-contract-template.handlebars

@@ -2,11 +2,13 @@
 // Copyright 2021 Vulcanize, Inc.
 //
 
+import path from 'path';
 import yargs from 'yargs';
 import 'reflect-metadata';
 import debug from 'debug';
 
 import { Config, DEFAULT_CONFIG_PATH, getConfig, initClients } from '@vulcanize/util';
+import { GraphWatcher, Database as GraphDatabase } from '@vulcanize/graph-node';
 
 import { Database } from '../database';
 import { Indexer } from '../indexer';
@@ -55,7 +57,16 @@ const main = async (): Promise<void> => {
   const db = new Database(config.database);
   await db.init();
 
-  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider);
+  const graphDb = new GraphDatabase(config.database, path.resolve(__dirname, 'entity/*'));
+  await graphDb.init();
+
+  const graphWatcher = new GraphWatcher(graphDb, postgraphileClient, config.server.subgraphPath);
+
+  const indexer = new Indexer(config.server, db, ethClient, postgraphileClient, ethProvider, graphWatcher);
+
+  graphWatcher.setIndexer(indexer);
+  await graphWatcher.init();
+
   await indexer.watchContract(argv.address, argv.kind, argv.checkpoint, argv.startingBlock);
 
   await db.close();

packages/codegen/src/utils/subgraph.ts

@@ -0,0 +1,58 @@
+import path from 'path';
+import assert from 'assert';
+import fs from 'fs';
+
+import { loadFilesSync } from '@graphql-tools/load-files';
+
+const SCALAR_MAPPING: any = {
+  BigDecimal: 'String',
+  Bytes: 'String'
+};
+
+export function parseSubgraphSchema (subgraphPath: string): any {
+  const subgraphSchemaPath = path.join(path.resolve(subgraphPath), '/schema.graphql');
+
+  assert(fs.existsSync(subgraphSchemaPath));
+  const typesArray = loadFilesSync(subgraphSchemaPath);
+
+  // Get a subgraph-schema DocumentNode with existing types.
+  const subgraphSchemaDocument = typesArray[0];
+  const subgraphTypeDefs = subgraphSchemaDocument.definitions;
+
+  subgraphTypeDefs.forEach((def: any) => {
+    // Remove type directives.
+    def.directives = [];
+
+    if (def.kind === 'ObjectTypeDefinition') {
+      def.fields.forEach((field: any) => {
+        // Remove field directives.
+        field.directives = [];
+
+        // Parse the field type.
+        field.type = parseType(field.type);
+      });
+    }
+  });
+
+  subgraphSchemaDocument.definitions = subgraphTypeDefs;
+
+  // Return a modified subgraph-schema DocumentNode.
+  return subgraphSchemaDocument;
+}
+
+function parseType (typeNode: any): any {
+  // Check if 'NamedType' is reached.
+  if (typeNode.kind === 'NamedType') {
+    const typeName: string = typeNode.name.value;
+
+    // TODO Handle extra types provided by the graph.
+    // Replace unknown scalars using SCALAR_MAPPING.
+    if (typeName in SCALAR_MAPPING) {
+      typeNode.name.value = SCALAR_MAPPING[typeName];
+    }
+  } else {
+    typeNode.type = parseType(typeNode.type);
+  }
+
+  return typeNode;
+}

packages/codegen/src/utils/type-mappings.ts

@@ -5,6 +5,7 @@
 const _solToTs: Map<string, string> = new Map();
 const _tsToGql: Map<string, string> = new Map();
 const _tsToPg: Map<string, string> = new Map();
+const _gqlToTs: Map<string, string> = new Map();
 
 // TODO Get typemapping from ethersjs.
 // Solidity to Typescript type-mapping.
@@ -23,10 +24,16 @@ _tsToGql.set('boolean', 'Boolean');
 
 // Typescript to Postgres type-mapping.
 _tsToPg.set('string', 'varchar');
-_tsToPg.set('number', 'numeric');
-_tsToPg.set('bigint', 'numeric');
+_tsToPg.set('number', 'integer');
+_tsToPg.set('bigint', 'bigint');
 _tsToPg.set('boolean', 'boolean');
 
+// Graphql to Typescript type-mapping.
+_gqlToTs.set('String', 'string');
+_gqlToTs.set('Int', 'number');
+_gqlToTs.set('BigInt', 'bigint');
+_gqlToTs.set('Boolean', 'boolean');
+
 function getTsForSol (solType: string): string | undefined {
   return _solToTs.get(solType);
 }
@@ -39,4 +46,8 @@ function getPgForTs (tsType: string): string | undefined {
   return _tsToPg.get(tsType);
 }
 
-export { getTsForSol, getGqlForTs, getPgForTs };
+function getTsForGql (gqlType: string): string | undefined {
+  return _gqlToTs.get(gqlType);
+}
+
+export { getTsForSol, getGqlForTs, getPgForTs, getTsForGql };

packages/codegen/src/visitor.ts

@@ -5,14 +5,15 @@
 import { Writable } from 'stream';
 
 import { Database } from './database';
-import { Param } from './utils/types';
-import { MODE_ETH_CALL, MODE_STORAGE } from './utils/constants';
 import { Entity } from './entity';
 import { Indexer } from './indexer';
 import { Resolvers } from './resolvers';
 import { Schema } from './schema';
 import { Client } from './client';
 import { Reset } from './reset';
+import { Param } from './utils/types';
+import { MODE_ETH_CALL, MODE_STORAGE } from './utils/constants';
+import { parseSubgraphSchema } from './utils/subgraph';
 
 export class Visitor {
   _schema: Schema;
@@ -106,6 +107,19 @@ export class Visitor {
     this._indexer.addEvent(name, params);
   }
 
+  visitSubgraph (subgraphPath?: string): void {
+    if (!subgraphPath) {
+      return;
+    }
+
+    // Parse subgraph schema to get subgraphSchemaDocument.
+    const subgraphSchemaDocument = parseSubgraphSchema(subgraphPath);
+
+    this._schema.addSubgraphSchema(subgraphSchemaDocument);
+    this._entity.addSubgraphEntities(subgraphSchemaDocument);
+    this._resolvers.addSubgraphResolvers(subgraphSchemaDocument);
+  }
+
   /**
    * Writes schema to a stream.
    * @param outStream A writable output stream to write the schema to.

packages/graph-node/src/database.ts

@@ -40,7 +40,7 @@ export class Database {
     return this._baseDatabase.close();
   }
 
-  async getEntity (blockHash: string, entity: string, id: string): Promise<any> {
+  async getEntity<Entity> (entity: (new () => Entity) | string, id: string, blockHash: string): Promise<Entity | undefined> {
     const queryRunner = this._conn.createQueryRunner();
     const repo = queryRunner.manager.getRepository(entity);
     const whereOptions: { [key: string]: any } = { id };

packages/graph-node/src/loader.ts

@@ -13,6 +13,8 @@ import {
   ContractInterface
 } from 'ethers';
 
+import { IndexerInterface } from '@vulcanize/util';
+
 import { TypeId } from './types';
 import { Block, fromEthereumValue, toEthereumValue } from './utils';
 import { Database } from './database';
@@ -36,7 +38,7 @@ export interface Context {
   }
 }
 
-export const instantiate = async (database: Database, context: Context, filePath: string, data: GraphData = {}): Promise<loader.ResultObject & { exports: any }> => {
+export const instantiate = async (database: Database, indexer: IndexerInterface, context: Context, filePath: string, data: GraphData = {}): Promise<loader.ResultObject & { exports: any }> => {
   const { abis = {}, dataSource } = data;
   const buffer = await fs.readFile(filePath);
   const provider = getDefaultProvider(NETWORK_URL);
@@ -48,7 +50,7 @@ export const instantiate = async (database: Database, context: Context, filePath
         const entityId = __getString(id);
 
         assert(context.event.block);
-        const entityData = await database.getEntity(context.event.block.blockHash, entityName, entityId);
+        const entityData = await database.getEntity(entityName, entityId, context.event.block.blockHash);
 
         if (!entityData) {
           return null;
@@ -64,6 +66,19 @@ export const instantiate = async (database: Database, context: Context, filePath
         assert(context.event.block);
         const dbData = await database.fromGraphEntity(exports, context.event.block, entityName, entityInstance);
         await database.saveEntity(entityName, dbData);
+
+        // Remove blockNumber and blockHash from dbData for auto-diff.
+        delete dbData.blockNumber;
+        delete dbData.blockHash;
+
+        // Prepare the diff data.
+        const diffData: any = { state: {} };
+        diffData.state[entityName] = dbData;
+
+        // Create an auto-diff.
+        assert(indexer.createDiffStaged);
+        assert(dataSource?.address);
+        await indexer.createDiffStaged(dataSource.address, context.event.block.blockHash, diffData);
       },
 
       'typeConversion.stringToH160': () => {

packages/graph-node/src/watcher.ts

@@ -2,6 +2,7 @@
 // Copyright 2021 Vulcanize, Inc.
 //
 
+import assert from 'assert';
 import 'reflect-metadata';
 import debug from 'debug';
 import path from 'path';
@@ -10,6 +11,7 @@ import { ContractInterface, utils } from 'ethers';
 
 import { ResultObject } from '@vulcanize/assemblyscript/lib/loader';
 import { EthClient } from '@vulcanize/ipld-eth-client';
+import { IndexerInterface } from '@vulcanize/util';
 
 import { createEvent, getSubgraphConfig } from './utils';
 import { Context, instantiate } from './loader';
@@ -24,6 +26,7 @@ interface DataSource {
 
 export class GraphWatcher {
   _database: Database;
+  _indexer?: IndexerInterface;
   _postgraphileClient: EthClient;
   _subgraphPath: string;
   _dataSources: any[] = [];
@@ -67,8 +70,10 @@ export class GraphWatcher {
 
       const filePath = path.join(this._subgraphPath, file);
 
+      assert(this._indexer);
+
       return {
-        instance: await instantiate(this._database, this._context, filePath, data),
+        instance: await instantiate(this._database, this._indexer, this._context, filePath, data),
         contractInterface
       };
     }, {});
@@ -144,7 +149,11 @@ export class GraphWatcher {
     await exports[eventHandler.handler](ethereumEvent);
   }
 
-  async getEntity (blockHash: string, entity: string, id: string): Promise<any> {
-    return this._database.getEntity(blockHash, entity, id);
+  setIndexer (indexer: IndexerInterface): void {
+    this._indexer = indexer;
+  }
+
+  async getEntity<Entity> (entity: new () => Entity, id: string, blockHash: string): Promise<Entity | undefined> {
+    return this._database.getEntity(entity, id, blockHash);
   }
 }

packages/util/src/types.ts

@@ -72,6 +72,7 @@ export interface IndexerInterface {
   parseEventNameAndArgs?: (kind: string, logObj: any) => any;
   isWatchedContract?: (address: string) => Promise<ContractInterface | undefined>;
   cacheContract?: (contract: ContractInterface) => void;
+  createDiffStaged?: (contractAddress: string, blockHash: string, data: any) => Promise<void>
 }
 
 export interface EventWatcherInterface {

yarn.lock

@@ -1102,6 +1102,15 @@
   dependencies:
     assemblyscript "0.19.10"
 
+"@graphql-tools/load-files@^6.5.2":
+  version "6.5.2"
+  resolved "https://registry.yarnpkg.com/@graphql-tools/load-files/-/load-files-6.5.2.tgz#9c7890b62d7c2958dc128b1d0c1dd84bb366b71f"
+  integrity sha512-ZU/v0HA7L3jCgizK5r3JHTg4ZQg+b+t3lSakU1cYT78kHT98milhlU+YF2giS7XP9KcS6jGTAalQbbX2yQA1sg==
+  dependencies:
+    globby "11.0.4"
+    tslib "~2.3.0"
+    unixify "1.0.0"
+
 "@graphql-typed-document-node/core@^3.0.0":
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/@graphql-typed-document-node/core/-/core-3.1.0.tgz#0eee6373e11418bfe0b5638f654df7a4ca6a3950"
@@ -7585,6 +7594,18 @@ globals@^9.18.0:
   resolved "https://registry.yarnpkg.com/globals/-/globals-9.18.0.tgz#aa3896b3e69b487f17e31ed2143d69a8e30c2d8a"
   integrity sha512-S0nG3CLEQiY/ILxqtztTWH/3iRRdyBLw6KMDxnKMchrtbj2OFmehVh0WUCfW3DUrIgx/qFrJPICrq4Z4sTR9UQ==
 
+globby@11.0.4:
+  version "11.0.4"
+  resolved "https://registry.yarnpkg.com/globby/-/globby-11.0.4.tgz#2cbaff77c2f2a62e71e9b2813a67b97a3a3001a5"
+  integrity sha512-9O4MVG9ioZJ08ffbcyVYyLOJLk5JQ688pJ4eMGLpdWLHq/Wr1D9BlriLQyL0E+jbkuePVZXYFj47QM/v093wHg==
+  dependencies:
+    array-union "^2.1.0"
+    dir-glob "^3.0.1"
+    fast-glob "^3.1.1"
+    ignore "^5.1.4"
+    merge2 "^1.3.0"
+    slash "^3.0.0"
+
 globby@^11.0.1, globby@^11.0.2:
   version "11.0.3"
   resolved "https://registry.yarnpkg.com/globby/-/globby-11.0.3.tgz#9b1f0cb523e171dd1ad8c7b2a9fb4b644b9593cb"
@@ -10449,6 +10470,13 @@ normalize-package-data@^3.0.0, normalize-package-data@^3.0.2:
     semver "^7.3.4"
     validate-npm-package-license "^3.0.1"
 
+normalize-path@^2.1.1:
+  version "2.1.1"
+  resolved "https://registry.yarnpkg.com/normalize-path/-/normalize-path-2.1.1.tgz#1ab28b556e198363a8c1a6f7e6fa20137fe6aed9"
+  integrity sha1-GrKLVW4Zg2Oowab35vogE3/mrtk=
+  dependencies:
+    remove-trailing-separator "^1.0.1"
+
 normalize-path@^3.0.0, normalize-path@~3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/normalize-path/-/normalize-path-3.0.0.tgz#0dcd69ff23a1c9b11fd0978316644a0388216a65"
@@ -12071,6 +12099,11 @@ regjsparser@^0.1.4:
   dependencies:
     jsesc "~0.5.0"
 
+remove-trailing-separator@^1.0.1:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/remove-trailing-separator/-/remove-trailing-separator-1.1.0.tgz#c24bce2a283adad5bc3f58e0d48249b92379d8ef"
+  integrity sha1-wkvOKig62tW8P1jg1IJJuSN52O8=
+
 repeat-element@^1.1.2:
   version "1.1.4"
   resolved "https://registry.yarnpkg.com/repeat-element/-/repeat-element-1.1.4.tgz#be681520847ab58c7568ac75fbfad28ed42d39e9"
@@ -13525,7 +13558,7 @@ tslib@^1.10.0, tslib@^1.8.1, tslib@^1.9.0, tslib@^1.9.3:
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.14.1.tgz#cf2d38bdc34a134bcaf1091c41f6619e2f672d00"
   integrity sha512-Xni35NKzjgMrwevysHTCArtLDpPvye8zV/0E4EyYn43P7/7qvQwPh9BGkHewbMulVntbigmcT7rdX3BNo9wRJg==
 
-tslib@^2.1.0:
+tslib@^2.1.0, tslib@~2.3.0:
   version "2.3.1"
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.3.1.tgz#e8a335add5ceae51aa261d32a490158ef042ef01"
   integrity sha512-77EbyPPpMz+FRFRuAFlWMtmgUWGe9UOG2Z25NqCwiIjRhOf5iKGuzSe5P2w1laq+FkRy4p+PCuVkJSGkzTEKVw==
@@ -13802,6 +13835,13 @@ universalify@^2.0.0:
   resolved "https://registry.yarnpkg.com/universalify/-/universalify-2.0.0.tgz#75a4984efedc4b08975c5aeb73f530d02df25717"
   integrity sha512-hAZsKq7Yy11Zu1DE0OzWjw7nnLZmJZYTDZZyEFHZdUhV8FkH5MCfoU1XMaxXovpyW5nq5scPqq0ZDP9Zyl04oQ==
 
+unixify@1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/unixify/-/unixify-1.0.0.tgz#3a641c8c2ffbce4da683a5c70f03a462940c2090"
+  integrity sha1-OmQcjC/7zk2mg6XHDwOkYpQMIJA=
+  dependencies:
+    normalize-path "^2.1.1"
+
 unorm@^1.3.3:
   version "1.6.0"
   resolved "https://registry.yarnpkg.com/unorm/-/unorm-1.6.0.tgz#029b289661fba714f1a9af439eb51d9b16c205af"