11/13/2023 0 Comments Ef psql commands![]() ![]() ![]() Schema | Name | Result data type | Argument data types | Type Also specify the name of the particular database you want to work in. Provide the correct path to the database directory with -D, or make sure that the environment variable PGDATA is set. postgres -single -D /usr/local/pgsql/data other-options mydatabase. You are now connected to database "db_3yn8kpgq9_3ynf8sbza" as user "user_3yn8kpgq9_3ynf8sbza". To start a single-user mode server, use a command like. Switch from aligned to non-aligned column output dotnet add package Microsoft.EntityFrameworkCore -version 6.0.0. ![]() Retrieve the current version of PostgreSQL serverĮg:to get detailed information on ALTER TABLE statement use the \h ALTER TABLE EntityFrameworkCore using the command shown as follows. List the database's current views that are available. The current database's available functions are listed. List every scheme in the connected database. Table_name Describe a table such as a column, type, modifiers of columns, etc. Psql -U user -h host “dbname=db sslmode=require” d: used to specify the name of the database We'll examine some of the most used Psql commands.īelow is a table containing the most used Psql commands:Ĭonnects to a database under a specific userĬonnect to a database on a different host. It is used to more quickly and efficiently query data from the PostgreSQL database server. An unhandled exception occurred while processing the request.Psql is a terminal that may be used to interface with the PostgreSQL database. The following is the resulting exception. ![]() Run the application and hit the ConcurrenctTest route which is for my test. After the above commands are run, the contents of the EFPostrgreSQL. This database provider allows EF Core to be used with PostgreSQL database. Var contactFromContext2 = context2.ContactsĬontactFromContext1.Address = () ĬontactFromContext2.Address = () Add the Entity Framework (EF) Core Npgsql package to the C project file. Var contactFromContext1 = context1.Contacts New ContactsDbContext(new DbContextOptionsBuilder() Please note that this function isn’t an example of how things should be done just a quick and dirty way to prove that the concurrency check is happening. be the argument(s) of ef, and neither variable interpolation nor backquote expansion. The first save will work and the second should fail. Thus you cannot mix SQL and psql meta-commands within a -c option. dotnet ef database update -context ContactsDbContext Testing it outįor a quick and dirty test, I added a ConcurrencyTest razor page under the Contacts directory. This function is going to ensure a specific contact exists, then pull the contact from two different DBContexts, make a mutation on the resulting contact objects, then attempt to save. Then, use the following command to apply the migration to your database. dotnet ef migrations add Concurrency -context ContactsDbContext This migration is a bit strange since the column technically already exists, but the migration seemed to be needed. NET CLI command to generate a migration for the above change. Next, from a command prompt in the same directory as your project file using the following. modelBuilder.Entity().ForNpgsqlUseXminAsConcurrencyToken() In the ContactDbContext add the following to the OnModelCreating function to enable concurrency checking on the specified entity, in this case, a Contact. The Postgres Entity Framework Core provide contains an extension that makes it very simple to use the xmin column as a concurrency token. If you read the official docs on Optimistic Concurrency and Concurrency Tokens you will find that all tables have an implicit/hidden system column call xmin which holds the ID of the latest updating transaction which means it gets changed automatically every time a row is changed. Any slash command ( \) is used to specify a meta-command that will typically run the necessary SQL queries in the background and return the results in a readable format. Unlike SQLite, Postgres has better built-in support for concurrency checks. Essential Usability Tips The psql utility is packed with many helpful commands to help you explore and manage your database. You can grab the sample code before any change here. This whole post will only be touch files found in the Postgres folder/project. This post is going to tackle concurrency checks using Postgres to keep the projects in the repo with the same level of functionality. Last week’s post on SQLite Concurrency Checks used this repo which contains examples of using Entity Framework Core with SQLite and Postgres. ![]()
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