In RethinkDB, what is the easiest way to check if a database or a table exists?

Question

One way I know I can do it is by listing throughdbList() and tableList() and then looking for what I want in the results.

Is there an easier way?

EDIT

My goal is to create a table in case it doesn't exist.

Growth

for example you can try to create table, if it's already exists, you will see error: RqlRuntimeError: Table already exists – Lobo

What are you trying to achieve? Do you want to create a database if it doesn't exist, or simply check if it exists? – Thorny

@Suvitruf, thanks for the reply. I wasn't really interested in throwing an error.. I just wanted to check whether it existed. – Growth

@Tholle, yes. I want to create a table in case it doesn't exist. – Growth

Answer 1

If you want to create a database if it does not exists, or get a value like "database already exists" if it does exist, you could do something like the following:

r.dbList().contains('example_database')
  .do(function(databaseExists) {
    return r.branch(
      databaseExists,
      { dbs_created: 0 },
      r.dbCreate('example_database')
    );
  }).run();

It will return the following if it is created:

{
  "config_changes": [
    {
      "new_val": {
        "id": "1ee7ddb4-6e2c-43bb-a0f5-64ef6a6211a8",
        "name": "example_database"
      },
      "old_val": null
    }
  ],
  "dbs_created": 1
}

And this if it already exists:

{
  "dbs_created": 0
}

Thorny

@Thorny why so complicated? my version with python: for table in self.tables: if not rdb.db(self.db).table_list().contains(table).run(): rdb.db(self.db).table_create(table).run() – Picklock

Answer 2

For the table existing checking I have found the following solution:

r.tableList().run(connection); //['people']

this will give you back an array of the tables which are defined on the default DB for example: ['people']. (if you want to set it do this: connection.use('test');)

then we can check if the array is containing our table name to create.

_.some(tableNames, tableName)

put it all together:

  if (!_.isNil(tableName) && _.isString(tableName) && !_.isNil(connection)) {
    r.tableList().run(connection).then(function(tableNames) {
      if (_.includes(tableNames, tableName)) {
        return r.tableCreate(tableName).run(connection);
      } else {
        return;
        }
    });
  }

Bronwen

Answer 3

In JavaScript, given an array of table names, the shortest way is

const tables = ['table1Name', 'table2Name', ...]
const db = 'myDb'

r(tables)
    .difference(r.db(db).tableList())
    .forEach(table => r.db(db).tableCreate(table))
    .run(connection)

Production

Don't you need a run() after r.db(db).tableList() ? – Relaxation

No you only need to call run at the end of your entire query – Production

Answer 4

For anyone coming from VB.net then solution would be like this.. one liner

Dim RDBDatabase as String = "dbName" 
Dim RDBTable as String = "tableName"  
   
Dim CheckDB = R.DbList().Contains(RDBDatabase).Do_(Function(databaseExists) R.Branch(databaseExists, "db done", R.DbCreate(RDBDatabase))).And(R.Db(RDBDatabase).TableList().Contains(RDBTable).Do_(Function(tableExists) R.Branch(tableExists, "tb done", R.Db(RDBDatabase).TableCreate(RDBTable)))).Run(conn)

This will create DB if it doesn't exists and will create the table if it doesn't exist

If neither exists then it will return values from the last created which is the table

{{
  "config_changes": [
    {
      "new_val": {
        "db": "dbName",
        "durability": "hard",
        "id": "0f72a570-7998-49f7-affc-96cbdd1ea086",
        "indexes": [],
        "name": "tableName",
        "primary_key": "id",
        "shards": [
          {
            "nonvoting_replicas": [],
            "primary_replica": "replicasssss_iu1",
            "replicas": [
              "replicasssss_iu1"
            ]
          }
        ],
        "write_acks": "majority"
      },
      "old_val": null
    }
  ],
  "tables_created": 1
}}

Alissaalistair