use dataloader to collect calls to DB fixes cap-js#30

lib/change-log.js

@@ -167,12 +167,12 @@ const _getChildChangeObjId = async function (
 const _formatCompositionContext = async function (changes, reqData) {
  const childNodeChanges = []
 
- for (const change of changes) {
+ await Promise.all(changes.map(async (change) => {
  if (typeof change.valueChangedTo === "object") {
  if (!Array.isArray(change.valueChangedTo)) {
  change.valueChangedTo = [change.valueChangedTo]
  }
- for (const childNodeChange of change.valueChangedTo) {
+ await Promise.all(change.valueChangedTo.map(async (childNodeChange) => {
  const curChange = Object.assign({}, change)
  const path = childNodeChange._path.split('/')
  const curNodePathVal = path.pop()
@@ -184,10 +184,10 @@ const _formatCompositionContext = async function (changes, reqData) {
  reqData
  )
  _formatCompositionValue(curChange, objId, childNodeChange, childNodeChanges)
- }
+ }))
  change.valueChangedTo = undefined
  }
- }
+ }))
  changes.push(...childNodeChanges)
 }
 
@@ -248,7 +248,7 @@ const _getObjectIdByPath = async function (
 
 const _formatObjectID = async function (changes, reqData) {
  const objectIdCache = new Map()
- for (const change of changes) {
+ await Promise.all(changes.map(async (change) => {
  const path = change.serviceEntityPath.split('/')
  const curNodePathVal = path.pop()
  const parentNodePathVal = path.pop()
@@ -276,7 +276,7 @@ const _formatObjectID = async function (changes, reqData) {
  change.entityID = curNodeObjId
  change.parentEntityID = parentNodeObjId
  change.parentKey = getUUIDFromPathVal(parentNodePathVal)
- }
+ }))
 }
 
 const _isCompositionContextPath = function (aPath, hasComp) {
@@ -290,6 +290,7 @@ const _isCompositionContextPath = function (aPath, hasComp) {
 }
 
 const _formatChangeLog = async function (changes, req) {
+ cds.context.dataloaders = {}
  await _formatObjectID(changes, req.data)
  await _formatAssociationContext(changes, req.data)
  await _formatCompositionContext(changes, req.data)
@@ -317,9 +318,9 @@ function _trackedChanges4 (srv, target, diff) {
  if (from === to) return
 
  /**
- * 
- * For the Inline entity such as Items, 
- * further filtering is required on the keys 
+ *
+ * For the Inline entity such as Items,
+ * further filtering is required on the keys
  * within the 'association' and 'foreign key' to ultimately retain the keys of the entity itself.
  * entity Order : cuid {
  * title : String;

lib/entity-helper.js

@@ -1,4 +1,5 @@
 const cds = require("@sap/cds")
+const DataLoader = require("dataloader");
 const LOG = cds.log("change-log")
 
 
@@ -22,18 +23,28 @@ const getEntityByContextPath = function (aPath, hasComp = false) {
 
 const getObjIdElementNamesInArray = function (elements) {
  if (Array.isArray(elements)) return elements.map(e => {
- const splitted = (e["="]||e).split('.')
+ const splitted = (e["="] || e).split('.')
  splitted.shift()
  return splitted.join('.')
  })
  else return []
 }
 
-const getCurObjFromDbQuery = async function (entityName, queryVal, /**optional*/ queryKey='ID') {
+const getCurObjFromDbQuery = async function (entityName, queryVal, /**optional*/ queryKey = 'ID') {
+ if (!(entityName in cds.context.dataloaders)) {
+ cds.context.dataloaders[entityName] = new DataLoader(async (keys) => {
+ // REVISIT: This always reads all elements -> should read required ones only!
+ const results = await SELECT.from(entityName).where(queryKey, 'in', keys)
+ const resultsByKey = results.reduce((acc, instance) => {
+ const key = instance[queryKey]
+ acc[key] = instance
+ return acc
+ }, {})
+ return keys.map(key => resultsByKey[key] || {})
+ })
+ }
  if (!queryVal) return {}
- // REVISIT: This always reads all elements -> should read required ones only!
- const obj = await SELECT.one.from(entityName).where({[queryKey]: queryVal})
- return obj || {}
+ return cds.context.dataloaders[entityName].load(queryVal)
 }
 
 const getCurObjFromReqData = function (reqData, nodePathVal, pathVal) {
@@ -71,21 +82,22 @@ const getCurObjFromReqData = function (reqData, nodePathVal, pathVal) {
 }
 
 
-async function getObjectId (reqData, entityName, fields, curObj) {
- let all = [], { curObjFromReqData: req_data={}, curObjFromDbQuery: db_data={} } = curObj
+async function getObjectId(reqData, entityName, fields, curObj) {
+ let all = [], {curObjFromReqData: req_data = {}, curObjFromDbQuery: db_data = {}} = curObj
  let entity = cds.model.definitions[entityName]
  if (!fields?.length) fields = entity["@changelog"]?.map?.(k => k['='] || k) || []
  for (let field of fields) {
  let path = field.split('.')
  if (path.length > 1) {
  let current = entity, _db_data = db_data
  while (path.length > 1) {
- let assoc = current.elements[path[0]]; if (!assoc?.isAssociation) break
+ let assoc = current.elements[path[0]];
+ if (!assoc?.isAssociation) break
  let foreignKey = assoc.keys?.[0]?.$generatedFieldName
  let IDval =
- req_data[foreignKey] && current.name === entityName
- ? req_data[foreignKey]
- : _db_data[foreignKey]
+  req_data[foreignKey] && current.name === entityName
+  ? req_data[foreignKey]
+  : _db_data[foreignKey]
  if (!IDval) {
  _db_data = {};
  } else try {
@@ -125,19 +137,18 @@ async function getObjectId (reqData, entityName, fields, curObj) {
 }
 
 
-
 const getDBEntity = (entity) => {
  if (typeof entity === 'string') entity = cds.model.definitions[entity]
  let proto = Reflect.getPrototypeOf(entity)
  if (proto instanceof cds.entity) return proto
 }
 
 const getValueEntityType = function (entityName, fields) {
- const types=[], entity = cds.model.definitions[entityName]
+ const types = [], entity = cds.model.definitions[entityName]
  for (let field of fields) {
  let current = entity, path = field.split('.')
  if (path.length > 1) {
- for (;;) {
+ for (; ;) {
  let target = current.elements[path[0]]?._target
  if (target) current = target; else break
  path.shift()
@@ -167,20 +178,20 @@ const hasComposition = function (parentEntity, subEntity) {
 }
 
 const _getCompositionObjFromReq = function (obj, targetID) {
-  if (obj?.ID === targetID) {
-  return obj;
-  }
+ if (obj?.ID === targetID) {
+ return obj;
+ }
 
- for (const key in obj) {
- if (typeof obj[key] === "object" && obj[key] !== null) {
- const result = _getCompositionObjFromReq(obj[key], targetID);
- if (result) {
- return result;
- }
- }
+ for (const key in obj) {
+ if (typeof obj[key] === "object" && obj[key] !== null) {
+ const result = _getCompositionObjFromReq(obj[key], targetID);
+ if (result) {
+ return result;
+ }
  }
+ }
 
-  return null;
+ return null;
 };
 
 module.exports = {

package.json

@@ -37,5 +37,8 @@
  "model": "@cap-js/change-tracking"
  }
  }
+ },
+ "dependencies": {
+ "dataloader": "^2.2.2"
  }
 }