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Hey, the problem you're experiencing is that when you join two tables in Athena, the query might scan all the data instead of just the relevant partitions. So, this happens because the query planner, which decides how to execute the query, might not recognize that it can skip some partitions based on your conditions.
When you swap the order of the tables in the join, the query planner can see which partitions to skip, so it scans less data. However, when you put this join in a view, the query planner loses this ability, and it scans all the data again.
To fix this, you can:
- Make sure your query clearly specifies which partitions it needs. For example, use
WHERE partition_day = '2024-03-09'
to tell the query planner to only look at data from March 9, 2024. - Keep your join conditions simple and related to the partition columns, so the query planner can easily understand which partitions are needed.
- Check how your query is executed using the
EXPLAIN
command in Athena, which can give you hints on why it's scanning all the data.
Additional Resource:
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