misc(clickhouse): Rewrite aggregation queries using Arel #3858
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jdenquin
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Jun 20, 2025
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Context
After some investigation in our quest to improve performances with Clickhouse database, it was found that in some condition, when computing events aggregation, many requests where sent to the Clickhouse cluster only to retrieve the tables structures.
This is happening specifically when calling
to_sqlon some queries built usingActiveRecord.These queries are not long to process but they uses some processor time on the cluster and as such cost money to Lago and slow down the aggregation processing especially when the cluster is under heavy load.
Description
As these queries can be easily avoided as they are not required for the aggregation, since the result relies only on a aggregated values rather than on a list of record, the decision was made to refactor the
Events::Stores::ClickhouseStoreto avoid usingto_sqlwhen writing queries and to rely as much as possible on pure SQL.To keep the ability to combine conditions and select, the rework was made using
Arelto rewrite the queries.