Arenadata Postgres

The simplest way to work with PostgreSQL tables is to use the psql terminal client. This client allows you to enter data queries, pass them to PostgreSQL, and view the results. Queries can also be received from a file or command line arguments. The psql tool becomes available on each node with the ADPG service immediately after the cluster installation.

PostgreSQL offers two types to store JSON data defined in RFC 7159: JSON and JSONB. To implement efficient query mechanisms for these data types, PostgreSQL also provides the JSONPath data type.

A common table expression (CTE) is a temporary result of an SQL statement that can be referenced in another SQL statement. CTEs allow you to split complex SQL queries into simpler parts.

User-defined PostgreSQL functions and procedures are designated to perform custom tasks. They are usually used to handle specific scenarios.

The SQL standard defines four levels of transaction isolation. The most strict is Serializable. According to the SQL standard, any concurrent execution of a set of Serializable transactions should produce the same effect as running them one at a time in some order. The other three levels are defined in terms of phenomena. These phenomena are the result of interactions between concurrent transactions.

A view is a named query stored in a database. PostgreSQL runs the query that defines the view every time the view is referenced. Views allow you to encapsulate the structure details of your tables, which might change as your application evolves, behind consistent interfaces.

ADPG/PostgreSQL provides various lock modes to control concurrent access to data in tables. Most PostgreSQL commands use locks of appropriate modes to ensure that referenced tables are not dropped or modified in incompatible ways while the command executes.

PostgreSQL creates an execution plan for each query. Since the resulting plan is critical to performance, PostgreSQL includes a complex planner that chooses the best plan based on an estimated cost of each alternative option.

A trigger is a specification that the ADPG/PostgreSQL should automatically execute a particular function whenever a certain type of operation is performed. Triggers can be attached to tables, views, and foreign tables.

ADPG uses roles to manage database access permissions. A role represents a database user or a group of database users. Roles can own database objects (for example, tables and functions) and allow access and actions on these objects (assign privileges).