SQL

Every issue on SQL

1. Document or Relational: Read-Time or Write-Time Cost11 Oct 2026

   Relational modeling describes the entities and lets queries follow. Document modeling inverts that, and the inversion is the whole trade.

2. Connection Pool Sizing: Why More Connections Make It Slower4 Oct 2026

   Past the point where the server can execute work in parallel, adding connections adds queueing rather than throughput — and moves the queue somewhere worse.

3. Composite Indexes: One Ordering, Not Three27 Sept 2026

   Column order decides which queries a composite index can serve. The rule follows from the structure, and so do the cases where it does not hold.

4. Why the Primary Key Is in Every Secondary Index20 Sept 2026

   InnoDB stores the table inside its primary key. Almost every MySQL indexing consequence, good and bad, follows from that single decision.

5. Transaction Pooling Breaks Only Under Load13 Sept 2026

   Transaction pooling is what makes PgBouncer worth deploying, and it silently removes session state your application may depend on.

6. EXPLAIN, ANALYZE, BUFFERS: Three Different Questions6 Sept 2026

   Which variant you ran decides whether the numbers in front of you are the planner's estimate or a measurement, and whether the pages came from cache.

7. N+1 Queries: What the ORM Is Actually Doing30 Aug 2026

   One query for the list, then one more for every item in it. The cost is per statement, which is why the profiler shows a fast database and a slow request.

8. Why an Index Is Not Used: the Estimate, Not the Index23 Aug 2026

   An index the planner ignores is usually a row-estimate problem. The fix starts with what the optimizer expected, not with the index definition.

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