activity-and-task-patterns

name	activity-and-task-patterns
description	Task and Event objects: polymorphic WhatId/WhoId, Activity object model, ActivityHistory vs OpenActivity, activity timeline customization, bulk task creation, Einstein Activity Capture boundaries. NOT for Calendar sharing (use calendar-sharing-setup). NOT for Email-to-Case (use case-management-setup).
category	admin
salesforce-version	Spring '25+
well-architected-pillars	["Reliability","Performance"]
tags	["task","event","activity","whatid","whoid","einstein-activity-capture"]
triggers	["task whatid whoid polymorphic lookup soql","why are some activities missing from the record activity timeline","bulk create tasks from apex dml best practice","activityhistory openactivity difference","einstein activity capture data storage and reporting","custom fields on activity task event sharing","salesforce task whatid whoid polymorphic typeof"]
inputs	["Objects requiring activity tracking","Volume of tasks/events generated per day","Einstein Activity Capture license status","Reporting requirements on activities"]
outputs	["Activity model decision (Task, Event, custom)","Polymorphic query patterns","Bulk creation pattern","Activity reporting approach"]
dependencies	[]
version	1.0.0
author	Pranav Nagrecha
updated	"2026-04-21T00:00:00.000Z"
status	stub

Activity and Task Patterns

Activate when designing interactions with Salesforce Activities — Task and Event records that attach to other objects via polymorphic WhatId and WhoId. The Activity object model is unusual: Activity is a read-only abstract parent, Task and Event are concrete children, and ActivityHistory / OpenActivity are read-only related lists, not queryable in bulk.

Before Starting

• Understand the Activity object model. Activity cannot be queried directly; query Task or Event. ActivityHistory and OpenActivity appear on related lists and subqueries only.
• Know the polymorphic fields. WhatId can reference any object enabled for activities; WhoId references Contact or Lead. Require TYPEOF or explicit type filters in SOQL.
• Check Einstein Activity Capture. EAC-captured emails/events are stored outside standard Task/Event and are not reportable the same way.

Core Concepts

Task vs Event

Task: to-do item with due date. Event: calendar appointment with start/end time. Both share the polymorphic WhatId / WhoId pattern and an IsTask discriminator on Activity queries.

Polymorphic SOQL

SELECT Id, Subject, What.Type, TYPEOF What
  WHEN Account THEN Name, Industry
  WHEN Opportunity THEN Amount, StageName
END FROM Task

Without TYPEOF, only ID and Type are accessible via What.Type.

ActivityHistory vs OpenActivity

ActivityHistory: closed activities (completed tasks, past events). OpenActivity: open activities (due, upcoming). Only queryable as subqueries from activity-enabled parents. Cannot create/update these objects directly.

Einstein Activity Capture

EAC syncs emails and calendar events from Exchange/Gmail into Salesforce. Data lives in a separate EAC store — visible on timeline, but not in Task/Event tables. Reporting requires Activity Metrics or EAC-specific features.

Common Patterns

Pattern: Bulk task creation from trigger

List<Task> tasks = new List<Task>();
for (Opportunity o : Trigger.new) {
    tasks.add(new Task(WhatId = o.Id, Subject = 'Review', ActivityDate = Date.today().addDays(7), OwnerId = o.OwnerId));
}
insert tasks;

Never loop-DML inside trigger; collect and insert once.

Pattern: Custom Object for high-volume activity-like data

If volume exceeds ~50k activities/day per object, consider a custom Interaction__c object with lookup instead of polymorphic Task. Better indexing, custom sharing, no Task-UI overhead.

Pattern: Activity rollup via Lightning component or Apex

Activity count / last-activity-date rollups: use formula-friendly patterns (e.g., Salesforce's Activity Metrics, EAC Insights, or DLRS).

Decision Guidance

Need	Approach
Standard to-do with reminders	Task
Calendar appointment with participants	Event
100k+ interactions per day	Custom Interaction__c object
Email tracking without EAC	EmailMessage + Task linking
Reporting on email activity	Activity Metrics or EAC Insights

Recommended Workflow

1. Inventory activity-generating processes; estimate daily volume per object.
2. If volume is modest and UI integration matters, use Task/Event.
3. For polymorphic queries, use TYPEOF and index-friendly WhatId filters.
4. Bulk-insert from triggers; never single-DML in loops.
5. Customize Activity Timeline via LWC or Flow for business-specific views.
6. Decide EAC vs manual logging; document where activity data lives.
7. Build reports using Task/Event + Activity Metrics; avoid querying ActivityHistory outside subqueries.

Review Checklist

• Activity volume estimated and matched to object choice
• Polymorphic SOQL uses TYPEOF or explicit type filters
• Bulk DML used for task/event creation
• ActivityHistory / OpenActivity queries only in subquery form
• EAC data strategy documented
• Custom fields on Activity limited (they propagate to both Task and Event)
• Sharing model for activities understood (inherits from WhatId parent)

Salesforce-Specific Gotchas

1. Custom fields on Activity propagate to both Task and Event. You cannot add a field only to Task — architect with this in mind.
2. Activities inherit sharing from the WhatId parent. No independent sharing rules.
3. OpenActivity and ActivityHistory cannot be modified. They are projections of Task/Event.

Output Artifacts

Artifact	Description
Activity model decision	Task vs Event vs custom object
SOQL pattern library	Polymorphic queries with TYPEOF
Bulk creation template	Apex trigger / batch pattern

Related Skills

• apex/apex-polymorphic-soql — polymorphic query patterns in depth
• admin/case-management-setup — case-related activity handling
• integration/einstein-activity-capture-integration — EAC data flow