Arthur Sepiol 34db34759f feat: implement automatic session linking and identity stitching (#3820) ... Links anonymous browser sessions to authenticated user identities, enabling unified user journey tracking across login boundaries. This solves the "logged-out anonymous session → logged-in session" tracking gap, providing complete funnel visibility and accurate visitor deduplication. ## Changes - Client-side: Persistent visitor ID in localStorage (data-identity-stitching attribute) - Server-side: identity_link table linking visitors to distinct IDs (authenticated users) - Query updates: getWebsiteStats now deduplicates by resolved identity - Graceful degradation: Works in Safari private browsing and when localStorage unavailable ## Implementation Details Uses hybrid approach combining client-side persistence with server-side linking: - Visitor ID generated once per browser, persists across sessions - When user logs in, identify() creates identity link - stats queries join through identity_link to deduplicate cross-device sessions Both PostgreSQL and ClickHouse supported with appropriate query patterns: - PostgreSQL: normalized schema, joins through session table - ClickHouse: denormalized with ReplacingMergeTree for deduplication ## Edge Cases Handled - Safari private browsing: localStorage throws, visitorId undefined, no link created - localStorage cleared: new visitorId generated, creates new link - Multiple tabs: same visitorId shared via localStorage - Multiple devices: one visitor can link to multiple distinct_ids - Multiple accounts: one distinct_id can link to multiple visitors ## Test Plan - [ ] Enable feature on test website (default enabled) - [ ] Anonymous pageview - confirm visitor_id in events table - [ ] Call umami.identify('user1') - confirm identity_link created - [ ] Stats show 1 visitor (deduplicated) - [ ] Log out, browse anonymously, stats still show 1 visitor - [ ] Test with data-identity-stitching="false" - no visitor_id collected - [ ] Test in Safari private browsing - no errors, gracefully skips - [ ] Test ClickHouse: verify identity_link table populated and FINAL keyword works - [ ] Verify retroactive: historical anonymous session attributed correctly		2025-12-03 16:54:56 +03:00
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clickhouse	feat: implement automatic session linking and identity stitching (#3820)	2025-12-03 16:54:56 +03:00
postgresql/data-migrations	New schema for pixels and links.	2025-08-13 20:27:54 -07:00