feat: Add projection for batch exports on inserted_at #21839
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tomasfarias
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Apr 25, 2024
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| uuid, | ||
| event, | ||
| properties, | ||
| timestamp, | ||
| team_id, | ||
| distinct_id, | ||
| elements_chain, | ||
| created_at, | ||
| person_id, | ||
| inserted_at, | ||
| _timestamp, | ||
| person_created_at, | ||
| person_properties |
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Fixed set of columns instead of * should make this lighter to materialize.
tomasfarias
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Apr 25, 2024
posthog/clickhouse/migrations/0059_inserted_at_batch_exports_projection.py
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Not going forward with this solution due to storage usage concerns, and ClickHouse projections being unreliable. Exploring a different solution that involves us writing the data somewhere else in different order (which is basically what a projection is, but to a more fitting storage). |
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Problem
The most confusing thing for batch export users is their data not appearing as it was ingested with a delay. Having a proper projection that sorts the data by
COALESCE(inserted_at, _timestamp)would allow us to remove any timestamp bounds that exclude events with delay, thus solving the problem. Also, it removes the need for a list of exceptions set viaUNCONSTRAINED_TIMESTAMP_TEAM_IDS.Changes
Adds projection, materializes last month. Only last month should work for ongoing realtime exports, we'll worry about backfills later.
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Does this work well for both Cloud and self-hosted?
How did you test this code?
Takes a second to create and materialize in ClickHouse cloud, what could go wrong?