Check the Existence of a Database

To check the existence of a database, we need to use a database context. The method Exists() in the DBsTxContext checks whether a given database already exists in the Orion cluster.

type DBsTxContext interface {
    ...
    ...
    // Exists checks whenever database is already created
    Exists(dbName string) (bool, error)
}

Source Code

The following code checks the existence of databases db1 and db2.

package main

import (
    "fmt"
)

func main() {
    db, err := createConnection()
    // if err is not nil, print and return

    session, err := openSession(db, "admin")
    // if err is not nil, print and return

    dbtx, err := session.DBsTx()
    // if err is not nil, print and return

    exist, err := dbtx.Exists("db1")
    // if err is not nil, print and return
    fmt.Println("Does database exist?", exist)

    exist, err = dbtx.Exists("db2")
    // if err is not nil, print and return
    fmt.Println("Does database exist?", exist)

    err = dbtx.Abort()
    // if err is not nil, print and return
}

Source Code Commentary

For the sake of simplicity, not all errors are handled in this code. Furthermore, the implementation of createConnection() and openSession() can be found here.

Calling session.DBsTx() starts a new database administration transaction and returns the database administration transaction context. Note that, in this example, we use this context only for the query purpose and not to perform any database administrative operation.

Calling dbtx.Exists("db1") and dbtx.Exists("db2") check whether the given databases exist or not. It returns a boolean flag where true denotes that the database exists, while false denotes that the database does not exist.

As we are executing a read-only query, it is not necessary to commit the transaction and hence, we can abort it by calling dbtx.Abort(). If we need to record all the read-only transactions history into the centralized ledger, then it is advisable to do dbtx.Commit() rather than dbtx.Abort().