Multi-database support (#869)

* Multi-database support

Initial version of multi-database support
* Github workflow: create multiple test databases
* `adapters/postgres/postgres_test.go`: Use dedicated `TestCase` table for
tests, to avoid `controllers/tables_test.go` to fail on unexpected data
(secondary database will only get some INSERTs those come from
context-aware tests, other data will end up in default database)
* `adapters/postgres/internal/connection/conn.go`: Removed unused varaible
* Updated comments explaining the logic around adding database
  connections to the pool
* Recently changed files re-formatted with `go fmt`
* + Added comments around tests for multi-database support

.github/workflows/test.yml

@@ -54,13 +54,15 @@ jobs:
           apt-get update
           apt-get install -y postgresql-client
 
-      - name: Setup Database
+      - name: Setup Databases
         env:
           PGPASSWORD: postgres
         run: |
-          psql -h $PREST_PG_HOST -p $PREST_PG_PORT -U $PREST_PG_USER -c "DROP DATABASE IF EXISTS \"$PREST_PG_DATABASE\";"
-          psql -h $PREST_PG_HOST -p $PREST_PG_PORT -U $PREST_PG_USER -c "CREATE DATABASE \"$PREST_PG_DATABASE\";"
-          psql -h $PREST_PG_HOST -p $PREST_PG_PORT -U $PREST_PG_USER -d $PREST_PG_DATABASE -f ./testdata/schema.sql
+          for db in $PREST_PG_DATABASE secondary-db; do
+            psql -h $PREST_PG_HOST -p $PREST_PG_PORT -U $PREST_PG_USER -c "DROP DATABASE IF EXISTS \"$db\";"
+            psql -h $PREST_PG_HOST -p $PREST_PG_PORT -U $PREST_PG_USER -c "CREATE DATABASE \"$db\";"
+            psql -h $PREST_PG_HOST -p $PREST_PG_PORT -U $PREST_PG_USER -d $db -f ./testdata/schema.sql
+          done
 
       - name: Set up Go
         uses: actions/setup-go@v4

adapters/postgres/connection.go

@@ -21,8 +21,8 @@ func GetPool() *connection.Pool {
 }
 
 // AddDatabaseToPool add connection to pool
-func AddDatabaseToPool(name string, DB *sqlx.DB) {
-	connection.AddDatabaseToPool(name, DB)
+func AddDatabaseToPool(name string) (*sqlx.DB, error) {
+	return connection.AddDatabaseToPool(name)
 }
 
 // MustGet get postgres connection

adapters/postgres/internal/connection/conn.go

@@ -13,7 +13,6 @@ import (
 )
 
 var (
-	err          error
 	pool         *Pool
 	currDatabase string
 )
@@ -55,25 +54,18 @@ func GetURI(DBName string) string {
 	return dbURI
 }
 
-// Get get postgres connection
+// Get get Postgres connection adding it to the pool if needed
 func Get() (*sqlx.DB, error) {
-	var DB *sqlx.DB
-
-	DB = getDatabaseFromPool(GetDatabase())
+	DB := getDatabaseFromPool(GetDatabase())
+	// Connection is already in the pool
 	if DB != nil {
 		return DB, nil
 	}
 
-	DB, err = sqlx.Connect("postgres", GetURI(GetDatabase()))
-	if err != nil {
-		return nil, err
-	}
-	DB.SetMaxIdleConns(config.PrestConf.PGMaxIdleConn)
-	DB.SetMaxOpenConns(config.PrestConf.PGMaxOpenConn)
-
-	AddDatabaseToPool(GetDatabase(), DB)
+	// Connection is not in the pool, add it
+	DB, err := AddDatabaseToPool(GetDatabase())
 
-	return DB, nil
+	return DB, err
 }
 
 // GetFromPool tries to get the db name from the db pool
@@ -108,13 +100,21 @@ func getDatabaseFromPool(name string) *sqlx.DB {
 	return DB
 }
 
-// AddDatabaseToPool add connection to pool
-func AddDatabaseToPool(name string, DB *sqlx.DB) {
+// AddDatabaseToPool create and add connection to the pool
+func AddDatabaseToPool(name string) (*sqlx.DB, error) {
+	DB, err := sqlx.Connect("postgres", GetURI(name))
+	if err != nil {
+		return nil, err
+	}
+	DB.SetMaxIdleConns(config.PrestConf.PGMaxIdleConn)
+	DB.SetMaxOpenConns(config.PrestConf.PGMaxOpenConn)
+
 	p := GetPool()
 
 	p.Mtx.Lock()
 	p.DB[GetURI(name)] = DB
 	p.Mtx.Unlock()
+	return DB, nil
 }
 
 // MustGet get postgres connection

adapters/postgres/postgres.go

@@ -1690,12 +1690,17 @@ func (adapter *Postgres) GetDatabase() string {
 	return connection.GetDatabase()
 }
 
-// getDBFromCtx tries to get the db from context if not present it will
-// fallback to the current setted db
+// getDBFromCtx tries to get the DB from context adding it to the pool if not
+// present, unless DB name is unset in the context - it will then fallback to
+// the current DB has been set via `SetDatabase(...)`
 func getDBFromCtx(ctx context.Context) (db *sqlx.DB, err error) {
 	dbName, ok := ctx.Value(pctx.DBNameKey).(string)
 	if ok {
-		return connection.GetFromPool(dbName)
+		DB, err := connection.GetFromPool(dbName)
+		if err == nil {
+			return DB, err
+		}
+		return connection.AddDatabaseToPool(dbName)
 	}
 	return connection.Get()
 }