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150 results
PostgreSQLAdvancedA one-line migration can freeze every query on a table. lock_timeout, CREATE INDEX CONCURRENTLY, NOT VALID constraints and expand-and-contract keep schema changes online.
#indexing#locking#migrations
GeneralIntermediateSelect-then-insert breaks under concurrency. Use a unique constraint plus one atomic statement: ON CONFLICT, ON DUPLICATE KEY UPDATE, or UPDLOCK/SERIALIZABLE in SQL Server.
#concurrency#schema-design#transactions
SQLiteBeginnerStill getting SQLITE_BUSY with a timeout set? The default timeout is zero and deferred transactions can't wait. WAL mode, busy_timeout and BEGIN IMMEDIATE fix most cases.
#concurrency#locking#troubleshooting
PostgreSQLIntermediateMVCC means Postgres doesn't store a row count. Make exact counts cheaper, get instant estimates from the planner, and keep exact counters when you really need them.
#internals#mvcc#performance
GeneralBeginnerThe N+1 query problem: each query takes 1 ms, but there are 301 of them. How to spot it, fix it with eager loading and avoid the cartesian-explosion overcorrection.
#orm#performance#troubleshooting
SQL ServerIntermediateExecution plans tell you exactly how SQL Server ran your query. Learn which operators matter, how to spot bad estimates and what the warnings really mean.
#execution-plans#performance#t-sql
PostgreSQLAdvancedEvery UPDATE in PostgreSQL leaves a dead row behind. Here's how MVCC works under the hood, what VACUUM cleans up, and how to keep autovacuum ahead of your workload.
#concurrency#internals#maintenance
SQL ServerAdvancedError 1205 again? Pull the deadlock graph from the system_health session, read it like a DBA and fix the access pattern that causes it.
#concurrency#locking#troubleshooting
SQL ServerBeginnerThe single most important physical design decision in SQL Server, explained from first principles — with the queries to prove it.
#indexing#performance#schema-design
SQL ServerIntermediateWhat each isolation level protects you from, what it costs, and why so many teams switch on READ_COMMITTED_SNAPSHOT.
#concurrency#locking#transactions
PostgreSQLIntermediateLearn to read PostgreSQL query plans node by node — estimates vs. actuals, loops, buffers — and turn them into index and query fixes.
#execution-plans#indexing#performance
