Amazon Official Blog Tables, Items, and Attributes The following are the basic DynamoDB components: Tables – Similar to other database systems, DynamoDB stores data in tables. A table is a collection of data. For example, see the example table called People that you could use to store personal contact information about friends, family, or anyone else of interest. You could… Continue reading DynamoDB
Category: Database
Pub Sub System
Event Driven architecture style Blog SO In an event driven architecture, you can use Redis and Kafka for pushing and subscribing to message. Below is a comparison - Redis pub-sub is mostly like a fire and forget system where all the messages you produced will be delivered to all the consumers at once and the… Continue reading Pub Sub System
Redis | Scan
Original O(N) Iterators: KEYS The Redis KEYS command returns all the keys in the database that match a pattern (or all the keys in the key space). Similar commands for fetching all the fields stored in a hash is HGETALL and for all fetching the members of a SMEMBERS. The keys in Redis themselves are stored in a dictionary (aka a hash table).… Continue reading Redis | Scan
Redis | Sentinel
Link It will monitor your master & slave instances, notify you about changed behaviour, handle automatic failover in case a master is down and act as a configuration provider, so your clients can find the current master instance. Redis Sentinel runs as a seperate program. You should have atleast 3 Sentinel instances monitoring a master instance and its slaves. Sentinel instances try… Continue reading Redis | Sentinel
Redis | Transactions |WATCH
Link MULTI, EXEC, DISCARD and WATCH are the foundation of transactions in Redis. They allow the execution of a group of commands in a single step, with two important guarantees: All the commands in a transaction are serialized and executed sequentially. It can never happen that a request issued by another client is served in the middle of the execution of a… Continue reading Redis | Transactions |WATCH
MySql | B + Tree
How does MySQL store data SO Link Indexes are a very important part of databases and are used frequently to speed up access to particular data item or items. So before working with indexes, it is important to understand how indexes work behind the scene and what is the data structure that is used to… Continue reading MySql | B + Tree
Managing Hierarchical Data in MySQL
Mysql – Having
As per SQL standard - The HAVING clause without a GROUP BY clause acts like the WHERE clause. If the HAVING clause contains no aggregate functions, use the WHERE clause for faster performance. SO Link here's an example of a SQL statement where we use HAVING: select column1 from table1 where condition1 having condition2; isn't it the same exact thing if we do this: select column1 from… Continue reading Mysql – Having
Mysql Basic Questions
What are the main differences between InnoDB and MyISAM? The InnoDB storage engine in MySQL. Support for transactions (giving you support for the ACID property). Row-level locking. Having a more fine grained locking-mechanism gives you higher concurrency compared to, for instance, MyISAM. Foreign key constraints. Allowing you to let the database ensure the integrity of the state of the database,… Continue reading Mysql Basic Questions
Database Sharding
SO Database sharding vs partitioning Sharding partitions spans across multiple database instances. So a table that is sharded has been partitioned, but a table that has been partitioned has not necessarily been sharded. Horizontal partitioning splits one or more tables by row, usually within a single instance of a schema and a database server. It… Continue reading Database Sharding
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