Handle entity duplicates in Mobile radio tracker #923
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kurotych
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michaeldjeffrey,
jeffgrunewald and
andymck
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| WITH unique_entity_keys AS ( | ||
| SELECT | ||
| kta.entity_key as entity_key, | ||
| kta.asset as asset, | ||
| MAX(mhi.refreshed_at) AS refreshed_at | ||
| FROM key_to_assets kta | ||
| INNER JOIN mobile_hotspot_infos mhi | ||
| ON kta.asset = mhi.asset | ||
| WHERE kta.entity_key IS NOT NULL | ||
| AND mhi.refreshed_at IS NOT NULL | ||
| GROUP BY kta.entity_key, kta.asset | ||
| ) |
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can this query be simplified back into something more like the original with a SELECT DISTINCT ON (entity_key, asset) ... ORDER BY refreshed_at DESC to limit results to the most recent single entry for that given combo of identifiers?
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Thank you for the hint. Now it is much better!
https://www.postgresql.org/docs/current/sql-select.html#SQL-DISTINCT
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During development testing, we encountered the following issue:
ERROR mobile_config::mobile_radio_tracker: error in tracking changes to mobile radios err=error returned from database: ON CONFLICT DO UPDATE command cannot affect row a second timeThe root cause of this problem is the existence of duplicate entity keys in the key_to_assets table (on the dev server).
Solution: Handle
(entity_key, asset)duplicates by fetching unique entries with the newerrefreshed_at.(Theoretically possible) Case where one entity_key maps to several different assets will still result in the error described above. Since I don't see a graceful recovery from such data corruption.