feat: Add pageview and prev pageview tracking

[robbie-c]

Changes

• Keep track of the last pagview event id
• Send the pageview event id with every event

This came from a discussion with @orian who wanted to be able to associate all of the query completed events that were triggered by the same pageview

Checklist

• Tests for new code (see advice on the tests we use)
• Accounted for the impact of any changes across different browsers
• Accounted for backwards compatibility of any changes (no breaking changes in posthog-js!)

[vercel]

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Name	Status	Preview	Updated (UTC)
posthog-js	✅ Ready (Inspect)	Visit Preview	Jan 3, 2025 0:51am

[github-actions]

Size Change: +4.38 kB (+0.14%)

Total Size: 3.23 MB

Filename	Size	Change
dist/array.full.es5.js	262 kB	+482 B (+0.18%)
dist/array.full.js	366 kB	+434 B (+0.12%)
dist/array.full.no-external.js	364 kB	+434 B (+0.12%)
dist/array.js	180 kB	+433 B (+0.24%)
dist/array.no-external.js	178 kB	+433 B (+0.24%)
dist/main.js	180 kB	+433 B (+0.24%)
dist/module.full.js	366 kB	+434 B (+0.12%)
dist/module.full.no-external.js	364 kB	+434 B (+0.12%)
dist/module.js	180 kB	+433 B (+0.24%)
dist/module.no-external.js	178 kB	+433 B (+0.24%)

ℹ️ View Unchanged

Filename	Size
dist/all-external-dependencies.js	206 kB
dist/customizations.full.js	12.6 kB
dist/dead-clicks-autocapture.js	14.4 kB
dist/exception-autocapture.js	9.48 kB
dist/external-scripts-loader.js	2.64 kB
dist/recorder-v2.js	115 kB
dist/recorder.js	115 kB
dist/surveys-preview.js	57.6 kB
dist/surveys.js	63.3 kB
dist/tracing-headers.js	1.76 kB
dist/web-vitals.js	10.4 kB

_{compressed-size-action}

[pauldambra]

brain is not fully engaged so sorry if this is a silly question

this is entirely in memory, no? so if my app does full page loads on navigation (i.e. not a SPA) then I won't have a previous pageview id?

or am i misunderstanding?

otherwise the logic for tracking it looks valid to me

[robbie-c]

This is true - I'll add a comment about why this is OK

[pauldambra]

nice! thank you! 💖

[pauldambra]

didn't run it but that looks safe and correct to me 🚀

[orian]

To query events and group the query ClickHouse' events table:

SELECT 
    JSONExtractString(properties, '$pageview_id') as pageview_id, 
    uuid, event, 
    timestamp,
    JSONExtractString(properties, 'duration'),
    JSONExtractString(properties, '$time'),
    properties
FROM events
WHERE team_id=1
    AND event='query completed' and timestamp > '2025-01-06'
    AND pageview_id <> ''
--    AND pageview_id = '<pageview id here>'
ORDER BY pageview_id
LIMIT 100;