add support for basic findOne with ID

README.md

@@ -36,3 +36,64 @@ context.prime(results);
 
 await User.findById(2, {[EXPECTED_OPTIONS_KEY]: context}); // Cached, if was in results
 ```
+
+## `findOne` batching
+
+`findOne` calls are automatically batched when a primary key is present in `where`. Multiple calls in the same tick are rewritten to a single `WHERE pk IN (...)` query:
+
+```js
+import {createContext, EXPECTED_OPTIONS_KEY} from 'dataloader-sequelize';
+const context = createContext(sequelize);
+
+// These execute in the same tick — batched into one query:
+User.findOne({ where: { id: 1 }, [EXPECTED_OPTIONS_KEY]: context });
+User.findOne({ where: { id: 2 }, [EXPECTED_OPTIONS_KEY]: context });
+// → SELECT * FROM users WHERE id IN (1, 2)
+```
+
+Extra conditions alongside the primary key are supported. Calls with identical extra conditions are batched together; different extra conditions use separate loaders:
+
+```js
+User.findOne({ where: { id: 1, status: 'active' }, [EXPECTED_OPTIONS_KEY]: context });
+User.findOne({ where: { id: 3, status: 'active' }, [EXPECTED_OPTIONS_KEY]: context });
+// → SELECT * FROM users WHERE id IN (1, 3) AND status = 'active'
+
+User.findOne({ where: { id: 2, status: 'inactive' }, [EXPECTED_OPTIONS_KEY]: context });
+// → SELECT * FROM users WHERE id IN (2) AND status = 'inactive'  (separate query)
+```
+
+Sequelize `Op` symbols are also supported:
+
+```js
+User.findOne({ where: { id: 1, [Op.and]: [{ deletedAt: null }] }, [EXPECTED_OPTIONS_KEY]: context });
+User.findOne({ where: { id: 2, [Op.and]: [{ deletedAt: null }] }, [EXPECTED_OPTIONS_KEY]: context });
+// → SELECT * FROM users WHERE id IN (1, 2) AND deletedAt IS NULL
+```
+
+## `BATCH_BY_ATTRIBUTE` — batching by any field
+
+For cases where you're not querying by primary key, use `BATCH_BY_ATTRIBUTE` to declare which field to batch by:
+
+```js
+import {createContext, EXPECTED_OPTIONS_KEY, BATCH_BY_ATTRIBUTE} from 'dataloader-sequelize';
+const context = createContext(sequelize);
+
+// Batch by a foreign key with a shared extra condition:
+Box.findOne({ where: { ancestorBoxId: 1, enabled: true }, [BATCH_BY_ATTRIBUTE]: 'ancestorBoxId', [EXPECTED_OPTIONS_KEY]: context });
+Box.findOne({ where: { ancestorBoxId: 2, enabled: true }, [BATCH_BY_ATTRIBUTE]: 'ancestorBoxId', [EXPECTED_OPTIONS_KEY]: context });
+Box.findOne({ where: { ancestorBoxId: 3, enabled: true }, [BATCH_BY_ATTRIBUTE]: 'ancestorBoxId', [EXPECTED_OPTIONS_KEY]: context });
+// → SELECT * FROM boxes WHERE ancestorBoxId IN (1, 2, 3) AND enabled = true
+```
+
+`order`, `raw`, `paranoid`, and `rejectOnEmpty` are all respected. Calls with different extra conditions or different `order` values use separate loaders and are not mixed:
+
+```js
+Box.findOne({
+  [EXPECTED_OPTIONS_KEY]: context,
+  [BATCH_BY_ATTRIBUTE]: 'ancestorBoxId',
+  order: [['id', 'DESC']],
+  rejectOnEmpty: true,
+  where: { ancestorBoxId: achievementReward.ancestorBoxId, enabled: true },
+});
+```
+

docker-compose.yml

@@ -1,18 +1,21 @@
-dev:
-  image: mhart/alpine-node:8.10
-  links:
-   - db
-  working_dir: /src
-  volumes:
-    - .:/src
-  environment:
-    DB_HOST: db
-    DB_DATABASE: dataloader_test
-    DB_USER: dataloader_test
-    DB_PASSWORD: dataloader_test
+version: '3.4'
 
-db:
-  image: postgres:9.4
-  environment:
-    POSTGRES_USER: dataloader_test
-    POSTGRES_PASSWORD: dataloader_test
+services:
+  dev:
+    image: mhart/alpine-node:8.10
+    links:
+    - db
+    working_dir: /src
+    volumes:
+      - .:/src
+    environment:
+      DB_HOST: db
+      DB_DATABASE: dataloader_test
+      DB_USER: dataloader_test
+      DB_PASSWORD: dataloader_test
+
+  db:
+    image: postgres:9.4
+    environment:
+      POSTGRES_USER: dataloader_test
+      POSTGRES_PASSWORD: dataloader_test

src/helper.js

@@ -8,7 +8,8 @@ export function methods(version) {
   return {
     findByPk: /^[56]/.test(version) ? ['findByPk'] :
               /^[4]/.test(version) ? ['findByPk', 'findById'] :
-              ['findById', 'findByPrimary']
+              ['findById', 'findByPrimary'],
+    findOne: ['findOne'],
   };
 }
 

src/index.js

@@ -1,10 +1,10 @@
-import Sequelize from 'sequelize';
-import shimmer from 'shimmer';
+import assert from 'assert';
 import DataLoader from 'dataloader';
-import {groupBy, property, values, clone, isEmpty, uniq} from 'lodash';
+import { clone, groupBy, isEmpty, property, uniq, values } from 'lodash';
 import LRU from 'lru-cache';
-import assert from 'assert';
-import {methods} from './helper';
+import Sequelize from 'sequelize';
+import shimmer from 'shimmer';
+import { methods } from './helper';
 
 const versionTestRegEx = /^[456]/;
 
@@ -176,9 +176,22 @@ function loaderForModel(model, attribute, attributeField, options = {}) {
   });
 }
 
+function loaderForFindOneWithConditions(model, attribute, otherWhere, options = {}) {
+  return new DataLoader(keys => {
+    const findOptions = Object.assign({}, options);
+    delete findOptions.rejectOnEmpty;
+    findOptions.where = Object.assign({ [attribute]: keys }, otherWhere);
+
+    return model.findAll(findOptions).then(mapResult.bind(null, attribute, keys, findOptions));
+  }, {
+    cache: options.cache
+  });
+}
+
 function shimModel(target) {
   if (target.findByPk ? target.findByPk.__wrapped : target.findById.__wrapped) return;
 
+  // findByPk
   shimmer.massWrap(target, methods(Sequelize.version).findByPk, original => {
     return function batchedFindById(id, options = {}) {
       if (options.transaction || options.include || activeClsTransaction() || !options[EXPECTED_OPTIONS_KEY]) {
@@ -204,6 +217,114 @@ function shimModel(target) {
       }).then(rejectOnEmpty.bind(null, options));
     };
   });
+
+  // findOne
+  shimmer.massWrap(target, methods(Sequelize.version).findOne, () => {
+    return function batchedFindOne(options = {}) {
+      const keys = Object.keys(options.where || {});
+      const symbolKeys = Object.getOwnPropertySymbols(options.where || {});
+      const id = options.where && options.where[this.primaryKeyAttribute];
+      const batchByAttribute = options[BATCH_BY_ATTRIBUTE];
+
+      if (options.transaction || options.include || activeClsTransaction() || !options[EXPECTED_OPTIONS_KEY]) {
+        const findOptions = Object.assign({ plain: true, rejectOnEmpty: false }, options);
+        if (findOptions.limit === undefined) {
+          const pkVal = findOptions.where && findOptions.where[this.primaryKeyAttribute];
+          if (!findOptions.where || !(typeof pkVal === 'number' || typeof pkVal === 'string' || Buffer.isBuffer(pkVal))) {
+            findOptions.limit = 1;
+          }
+        }
+        return this.findAll(findOptions);
+      }
+
+      // BATCH_BY_ATTRIBUTE path: user explicitly declares which field to batch by
+      if (batchByAttribute) {
+        const batchValue = options.where && options.where[batchByAttribute];
+        if (!['string', 'number'].includes(typeof batchValue)) {
+          const findOptions = Object.assign({ plain: true, rejectOnEmpty: false }, options);
+          if (findOptions.limit === undefined) findOptions.limit = 1;
+          return this.findAll(findOptions);
+        }
+
+        return Promise.resolve().then(() => {
+          const loaders = options[EXPECTED_OPTIONS_KEY].loaders;
+          const otherWhere = Object.assign({}, options.where);
+          delete otherWhere[batchByAttribute];
+
+          const loaderOptions = { where: otherWhere, order: options.order, raw: options.raw, paranoid: options.paranoid };
+          const cacheKey = getCacheKey(this, batchByAttribute, loaderOptions);
+          let loader = loaders.autogenerated.get(cacheKey);
+          if (!loader) {
+            loader = loaderForFindOneWithConditions(this, batchByAttribute, otherWhere, {
+              order: options.order,
+              raw: options.raw,
+              paranoid: options.paranoid,
+              logging: options.logging,
+              cache: true
+            });
+            loaders.autogenerated.set(cacheKey, loader);
+          }
+          return loader.load(batchValue);
+        }).then(rejectOnEmpty.bind(null, options));
+      }
+
+      if (!['string', 'number'].includes(typeof id)) {
+        // Call this.findAll() directly rather than the original findOne, because
+        // Sequelize v3's findOne internally calls Model.prototype.findAll (bypassing
+        // instance-level overrides like sinon spies). Calling this.findAll() with the
+        // same options findOne would use is semantically equivalent across all versions.
+        const findOptions = Object.assign({ plain: true, rejectOnEmpty: false }, options);
+        if (findOptions.limit === undefined) {
+          const pkVal = findOptions.where && findOptions.where[this.primaryKeyAttribute];
+          if (!findOptions.where || !(typeof pkVal === 'number' || typeof pkVal === 'string' || Buffer.isBuffer(pkVal))) {
+            findOptions.limit = 1;
+          }
+        }
+        return this.findAll(findOptions);
+      }
+
+      return Promise.resolve().then(() => {
+        if ([null, undefined].indexOf(id) !== -1) {
+          return Promise.resolve(null);
+        }
+
+        const loaders = options[EXPECTED_OPTIONS_KEY].loaders;
+
+        if (keys.length === 1 && symbolKeys.length === 0) {
+          // Simple case: only PK in where — use byPrimaryKey loader
+          let loader = loaders[this.name].byPrimaryKey;
+          if (options.raw || options.paranoid === false) {
+            const cacheKey = getCacheKey(this, this.primaryKeyAttribute, { raw: options.raw, paranoid: options.paranoid });
+            loader = loaders.autogenerated.get(cacheKey);
+            if (!loader) {
+              loader = createModelAttributeLoader(this, this.primaryKeyAttribute, { raw: options.raw, paranoid: options.paranoid, logging: options.logging });
+              loaders.autogenerated.set(cacheKey, loader);
+            }
+          }
+          return loader.load(id);
+        } else {
+          // Extended case: PK + extra conditions — batch calls with identical extra conditions together
+          const otherWhere = Object.assign({}, options.where);
+          delete otherWhere[this.primaryKeyAttribute];
+
+          const loaderOptions = { where: otherWhere, order: options.order, raw: options.raw, paranoid: options.paranoid };
+          const cacheKey = getCacheKey(this, this.primaryKeyAttribute, loaderOptions);
+          let loader = loaders.autogenerated.get(cacheKey);
+          if (!loader) {
+            loader = loaderForFindOneWithConditions(this, this.primaryKeyAttribute, otherWhere, {
+              order: options.order,
+              raw: options.raw,
+              paranoid: options.paranoid,
+              logging: options.logging,
+              cache: true
+            });
+            loaders.autogenerated.set(cacheKey, loader);
+          }
+          return loader.load(id);
+        }
+      }).then(rejectOnEmpty.bind(null, options));
+    };
+  });
 }
 
 function shimBelongsTo(target) {
@@ -425,6 +546,7 @@ function activeClsTransaction() {
 }
 
 export const EXPECTED_OPTIONS_KEY = 'dataloader_sequelize_context';
+export const BATCH_BY_ATTRIBUTE = 'dataloader_sequelize_batch_by_attribute';
 export function createContext(sequelize, options = {}) {
   const loaders = {};
 

test/helper.js

@@ -19,7 +19,8 @@ export function createConnection() {
     process.env.DB_PASSWORD, {
       dialect: 'postgres',
       host: process.env.DB_HOST,
-      logging: false
+      logging: false,
+      pool: { max: 1, min: 0, idle: 10000 }
     }
   );