Do sequences affect database query performance

1. Overhead from Sequence Calls: Each call to a sequence (such as `NEXTVAL` in Oracle) can introduce overhead, especially if it is called frequently in a loop or bulk operation. For example, performance issues have been noted when sequences are heavily used in recursive SQL contexts, leading to significant overhead due to the synchronous nature of these calls[2].

2. Impact on Query Plans: The sequence of index creation and its management can influence the execution plans generated by the database optimizer. If the sequence of operations or the order of index creation is not optimal, it may lead to the selection of less efficient query plans, which can degrade performance[1].

3. Caching Behavior: The configuration of sequences, such as the `CACHE` value in Oracle, can significantly impact performance. A low cache setting may lead to more frequent disk I/O operations, while a higher cache setting can improve performance by reducing the number of times the database needs to access the disk for sequence values[2][3].

4. Concurrency Issues: In high-concurrency environments, sequences can become a bottleneck if many transactions are trying to access the same sequence simultaneously. This contention can lead to delays and increased response times for queries that rely on sequence values[2].

5. Resource Consumption: Using sequences extensively can lead to increased resource consumption, such as CPU and memory usage, especially when generating large datasets. This can affect overall database performance if not managed properly[2].

6. Query Structure and Design: The way queries are structured can also impact how sequences affect performance. Optimizing queries to minimize unnecessary calls to sequences can lead to better performance outcomes[5].

In summary, while sequences are generally efficient, their impact on database query performance can vary based on their usage, configuration, and the overall database design. Proper management and optimization strategies are essential to mitigate potential performance issues associated with sequences.