How to Efficiently Get Total Result Count in Paginated Queries without Multiple SQL Queries?

Optimizing Paginated Queries: Obtaining Total Result Count Efficiently

Efficient pagination requires knowing the total number of results to accurately display pagination controls. The conventional method involves two separate queries: one to count all results and another to fetch the current page's data. This approach, however, can be inefficient.

A More Efficient SQL Approach

PostgreSQL offers a superior solution leveraging window functions (available since version 8.4). The COUNT(*) OVER() function allows retrieval of both the total count and the paginated results within a single query:

<code class="language-sql">SELECT foo,
       COUNT(*) OVER() AS full_count
FROM   bar
WHERE  <some condition>
ORDER  BY <some col>
LIMIT  <pagesize>
OFFSET <offset>;</code>

It's crucial to note that this method, while elegant, can impact performance on very large tables due to the full row count calculation. Careful consideration of performance trade-offs is necessary.

Alternative Strategies for Performance Optimization

For improved performance with large datasets, consider these alternatives:

• Utilizing PostgreSQL's internal mechanisms to retrieve the affected row count via client-side functions like GET DIAGNOSTICS and pg_num_rows.
• Optimizing queries that utilize OFFSET on extensive tables to enhance efficiency. This may involve indexing strategies or alternative query structures.

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