When users query a Hive table partitioned on a specific column (in your case, "source system name") but do not include a filter condition on that partition column in their queries, Hive may need to scan all partitions of the table to retrieve the relevant data. This can lead to less efficient query performance, as it requires reading unnecessary data from multiple partitions.
In your scenario, where you perform frequent insert overwrites to keep only the current data, the table may not grow drastically in terms of total data volume. However, if the users frequently query the table without specifying the partition column condition, it can still result in increased query processing time and resource utilisation.
To improve query efficiency in this situation, you have a few options:
Partition Pruning: Encourage users to include the partition column condition in their queries. Hive has built-in partition pruning optimization, which allows it to skip unnecessary partitions when the partition column condition is provided.
Materialized Views: If certain common query patterns exist, consider creating materialized views that pre-aggregate or pre-filter data based on those patterns. This can significantly speed up queries that align with the materialized views.
Optimize Data Layout: Ensure that the data is stored efficiently, and consider using columnar storage formats like ORC or Parquet, which can improve query performance.
Ultimately, the choice of optimization strategy depends on the specific usage patterns and requirements of your users. It's essential to monitor query performance and understand your users' query behavior to determine which optimization approaches are most effective.
