Unlike RDBMS databases, Cassandra will not do in place update, delete or any modification, deletes are also kind of inserts and it will follow the rule of Last Write Wins(LWW). The data is always written to the immutable files called SSTABLES, In the context of Cassandra, a tombstone is specific data stored alongside standard data. […]
Troubleshooting network connectivity issues like connection refused or connection is hanging due to port issues. Step 1. Verify ping time from both ends(source and destination) ping 10.10.10.11 Ping time of 100 ms and below are average for most broadband connections. So there will not be any lag. While a ping of 150 ms or more may not […]
Cassandra memory consist of Heap memory + Off Heap Memory Off-Heap Memory(Native Memory or Direct memory, which is managed by OS) Heap Memory(Which is managed by Java) Following are the part of Off-Heap Memory Partition key Cache Row cache Chunk cache Memtable space Note:Depending upon memtable_allocation_type memtable, space can be in off-heap or in heap […]
This article is about the access paths in PostgreSQL, and I am trying to relate them with Oracle access paths, which helps Oracle DBA’s to understand access paths in PostgreSQL and vice versa. To be clear, I am not comparing the algorithms behind these access paths in the article. Sequential Scan in PostgreSQL / Table […]
Tablespaces in PostgreSQL helps to define or link the directory on the physical disk where the files of the objects(tables) are stored.In Oracle, tablespaces are not links to the directory, tablespaces linked to physical files, and are allocated to a schema in a database so that all the tables created in that schema are stored […]
Users are not schemas in PostgreSQL. Schemas in PostgreSQL are different entities, a schema in PostgreSQL sits under a database and a schema is always assigned to a user.We can assign more than one schema to a user.In PostgreSQL, it is a good practice to create a schema for each user with the same name […]
Step 1 psql –connect using super user Step 2 Check if the archive mode is turned on cluster. show archive_modeshow archive_commandshow wal_level Step 2 Modify the following in postgressql.conf to turn on archive mode wal_level = replicaarchive_mode = onarchive_command= ‘test ! -f /Library/PostgreSQL/12/data/archive/%f && cp %p /Library/PostgreSQL/12/data/archive/%f’ —-Path of the archive files Step 3 Restart […]
This article will provide details of the automatic stats collector job in PostgreSQL and Oracle POSTGRESQL […]
In PostgreSQL, the old version rows or dead tuples or obsolete records that are generated due to delete and update will not release the space unless the table is vacuumed. The vacuum helps to release the space occupied by obsolete records but the released space will be under table or segment. These blocks will be […]