[cypress] PostgreSQL Connection pool for System Tests (#43924)

* Use Connection pool for PostgreSQL in System Tests

Sometimes single specs in the System Tests fail with:
    CypressError: `cy.task('queryDB')` failed with the following error:
    > duplicate key value violates unique constraint "cpostgresmax_users_pkey"

The error happens on different specs in System Tests especially running on drone.
It could be reproduced in running the System Tests tree times (first with installation, 2nd and 3rd run w/o):
    npx cypress run
    npx cypress run --spec 'tests/System/integration/administrator/**/*.cy.{js,jsx,ts,tsx},tests/System/integration/site/**/*.cy.{js,jsx,ts,tsx},tests/System/integration/api/**/*.cy.{js,jsx,ts,tsx},tests/System/integration/plugins/**/*.cy.{js,jsx,ts,tsx}'
    npx cypress run --spec 'tests/System/integration/administrator/**/*.cy.{js,jsx,ts,tsx},tests/System/integration/site/**/*.cy.{js,jsx,ts,tsx},tests/System/integration/api/**/*.cy.{js,jsx,ts,tsx},tests/System/integration/plugins/**/*.cy.{js,jsx,ts,tsx}'

Checking the session usage in pgAdmin shows the maximum number of 100 configured sessions appears to have been reached.
Therefore the usage of postgres connection pool is implemented.
The session usage is reduced to max 12 and the error could no more reproduced.

* Simplify implementation

- Delete function as only called once
- Renamed to postgresConnectionPool

Contributed by @laoneo

---------

Co-authored-by: Allon Moritz <allon.moritz@digital-peak.com>

tests/System/plugins/db.mjs

@@ -4,6 +4,10 @@ import postgres from 'postgres';
 // Items cache which are added by an insert statement
 let insertedItems = [];
 
+// Use of the PostgreSQL connection pool to limit the number of sessions, see
+// https://github.com/porsager/postgres?tab=readme-ov-file#connection-details
+let postgresConnectionPool = null;
+
 /**
  * Does run the given query against the database from the configuration. It caches all inserted items.
  *
@@ -29,17 +33,20 @@ function queryTestDB(joomlaQuery, config) {
     insertedItems.push(insertItem);
   }
 
-  // Check if the DB is from postgres
+  // Do we use PostgreSQL?
   if (config.env.db_type === 'pgsql' || config.env.db_type === 'PostgreSQL (PDO)') {
-    const connection = postgres({
-      host: config.env.db_host,
-      port: config.env.db_port,
-      database: config.env.db_name,
-      username: config.env.db_user,
-      password: config.env.db_password,
-      idle_timeout: 1,
-      max_lifetime: 1,
-    });
+
+    if (postgresConnectionPool === null) {
+      // Initialisation on the first call
+      postgresConnectionPool = postgres({
+        host: config.env.db_host,
+        port: config.env.db_port,
+        database: config.env.db_name,
+        username: config.env.db_user,
+        password: config.env.db_password,
+        max: 10, // Use only this (unchanged default) maximum number of connections in the pool
+      });
+    }
 
     // Postgres delivers the data direct as result of the insert query
     if (insertItem) {
@@ -49,7 +56,7 @@ function queryTestDB(joomlaQuery, config) {
     // Postgres needs double quotes
     query = query.replaceAll('`', '"');
 
-    return connection.unsafe(query).then((result) => {
+    return postgresConnectionPool.unsafe(query).then((result) => {
       // Select query should always return an array
       if (query.indexOf('SELECT') === 0 && !Array.isArray(result)) {
         return [result];
@@ -64,12 +71,12 @@ function queryTestDB(joomlaQuery, config) {
         insertItem.rows.push(result[0].id);
       }
 
-      // Normalize the object
+      // Normalize the object and return from PostgreSQL
       return { insertId: result[0].id };
     });
   }
 
-  // Return a promise which runs the query
+  // Return a promise which runs the query for MariaDB / MySQL
   return new Promise((resolve, reject) => {
     // Create the connection and connect
     const connection = mysql.createConnection({
@@ -94,7 +101,7 @@ function queryTestDB(joomlaQuery, config) {
         insertItem.rows.push(results.insertId);
       }
 
-      // Resolve the result
+      // Resolve the result from MariaDB / MySQL
       return resolve(results);
     });
   });