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PostgreSQL

Overview

PostgreSQL is a free and open-source relational database management system. It can be accessed and manipulated using SQL to extract or load data.

Integration Use Cases

PostgreSQL databases are great for those looking to configure their own database and can be used to feed into reports and analytics.

Example user stories:

  • As an NGO program manager, I would like to be able to automatically see cases registered in our case-management system in a Postgres database which is connected to a visualization dashboard.
  • As a fundraiser at an NGO, I would like to see all consumption data in Postgres so I can better monitor activities in real-time.

Integration Options

OpenFn adaptors (see language-postgresql) provide direct database connections for accessing data and executing SQL and standard database operations.

Authentication:

To create the direct DB connection, you'll need to specify the following credential inputs.

{
"configuration": {
"host": "some-host-url.compute-1.amazonaws.com",
"port": "5432",
"database": "testdatabase",
"user": "myusername",
"password": "testing123",
"ssl": true,
"allowSelfSignedCert": true
}
}

(This authentication step is handled in the OpenFn adaptor.)

Sample Job Expressions:

This function creates a table users in a database from a given array of columns.

insertTable('users', state =>
state.data.map(column => ({
name: column.name,
type: column.type,
required: true, // optional
unique: false, // optional - set to true for unique constraint
}))
);

This function is used to insert a single record in a Postgres database.

insert(
'users',
{
email: 'antony@gmail.com',
first_name: 'Antony',
inserted_at: '2020-08-27 00:00:00',
updated_at: '2020-08-27 00:00:00',
},
{ setNull: ["''", "'undefined'"], writeSql: true, logValues: true }
);

See the Job Library for more sample jobs.

Integration tips

  • Keys: Make sure the primary key and foreign keys for each table are known documented in the mapping specifications
  • Unique identifiers: To avoid the "ON CONFLICT DO UPDATE command cannot affect row a second time" error discussed below, spend time thinking through which field or combination of fields makes each record unique using the sample data recieved
  • Testing: Create a robust test suite which outlines which tables should be updated by each job run image

Common Errors

  1. Connection TIMEOUT - This error usually means the destination system is offline or inaccessible to your user. Contact the destination system administrator.
  2. error: value too long for type character varying(16) & error: null value in column "household_id" violates not-null constraint - Both of these errors highlight a mismatch in the data you're attempting to add to the database and what it's configured to accept. In this case, you are sending more than 16 characters for a field that only accepts up to 16 characters AND sending "null" for a required field in that table.
  3. error: ON CONFLICT DO UPDATE command cannot affect row a second time- This error means that there are two rows with the same value for unique fields. Review the sample data and mapping specifications to decide what makes a record unique in that table.

OpenFn Adaptors

OpenFn implementations can leverage the PostgreSQL adaptor.

Implementation Examples

  1. Wildlife Conservation Society Kobo < > Database: https://github.com/OpenFn/consosci
  2. Cambodia Primero < > ONA Database: https://github.com/OpenFn/primero-ona-dashboard