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Concept Overview Redis Publish/Subscribe (Pub/Sub) implements a messaging paradigm where senders (publishers) transmit messages to channels, and receivers (subscribers) listen for messages on those channels. A single Redis client can subscribe to multiple channels simultaneously. When a message is published to a channel, all active subscribers ...

InnoDB serves as MySQL's default storage engine and supports full transaction capabilities. Every operation runs within a transaction context; explicit BEGIN or START TRANSACTION statements start user-defined transactions, while implicit ones are created automatically for individual statements when not explicitly managed. MySQL defines four tra ...

Concurrency Programming Essentials Thread Lifecycle States NEW: Initial state after thread creation but before start() invocation RUNNABLE: Combined ready/running state in JVM terminology BLOCKED: Occurs when a thread fails to acquire a synchronized lock WAITING: Indefinite pause triggered by wait(), join(), or I/O operations TIMED_WAITING: Te ...

Predicate Pushdown to SeqScan Integrate the Filter operator above the SeqScan operator into SeqScan itself, allowing the system to lock only rows that satisfy the predicate. Modify the Next() function in SeqScanExecutor: auto SeqScanExecutor::Next(Tuple *result_tuple, RID *result_rid) -> bool { do { if (table_iterator_ == table_info_-& ...

Concurrency Strategy in B+Trees Implementing thread safety in a B+Tree index requires protecting both the internal data of nodes and the structural integrity during split and merge operations. The standard protocol for this is Latch Crabbing, where a thread acquires a latch on a child node and only releases the latch on the parent if the child ...

Introduction Databases serve multiple concurrent users. When several transactions access the same data simultaneously, controlling concurrency becomes essential to prevent data corruption and maintain consistency. Locks are the fundamental mechanism Oracle uses to enforce data integrity and isolate transactions. Unlike some RDBMS that maintain ...