PowerShell Scripting to Replicate MongoDB Data to MySQL

The CData Cmdlets for MongoDB offer live access to MongoDB data from within PowerShell. Using PowerShell scripts, you can easily automate regular tasks like data replication. This article will walk through using the CData Cmdlets for MongoDB and the CData Cmdlets for MySQL in PowerShell to replicate MongoDB data to a MySQL database.

After obtaining the needed connection properties, accessing MongoDB data in PowerShell and preparing for replication consists of four basic steps.

Set the Server, Database, User, and Password connection properties to connect to MongoDB. To access MongoDB collections as tables you can use automatic schema discovery or write your own schema definitions. Schemas are defined in .rsd files, which have a simple format. You can also execute free-form queries that are not tied to the schema.

Collecting MongoDB Data

1. Install the module:

   Install-Module MongoDBCmdlets

2. Connect to MongoDB:

   $mongodb = Connect-MongoDB -Server $Server -Port $Port -Database $Database -User $User -Password $Password

3. Retrieve the data from a specific resource:

   $data = Select-MongoDB -Connection $mongodb -Table "restaurants"

   You can also use the Invoke-MongoDB cmdlet to execute pure SQL-92 statements:

   $data = Invoke-MongoDB -Connection $mongodb -Query 'SELECT * FROM restaurants WHERE Name = @Name' -Params @{'@Name'='Morris Park Bake Shop'}

4. Save a list of the column names from the returned data.

   $columns = ($data | Get-Member -MemberType NoteProperty | Select-Object -Property Name).Name

Inserting MongoDB Data into the MySQL Database

With the data and column names collected, you are ready to replicate the data into a MySQL database.

1. Install the module:

   Install-Module MySQLCmdlets

2. Connect to MySQL, using the server address and port of the MySQL server, valid user credentials, and a specific database with the table in which the data will be replicated:

   $mysql = Connect-MySQL -User $User -Password $Password -Database $Database -Server $Server -Port $Port

3. Loop through the MongoDB data, store the values, and use the Add-MySQL cmdlet to insert the data into the MySQL database, one row at a time. In this example, the table will need to have the same name as the MongoDB resource (restaurants) and to exist in the database.

   $data | % { $row = $_ $values = @() $columns | % { $col = $_ $values += $row.$($col) } Add-MySQL -Connection $mysql -Table "restaurants" -Columns $columns -Values $values }

You have now replicated your MongoDB data to a MySQL database. This gives you freedom to work with MongoDB data in the same way that you work with other MySQL tables, whether that is performing analytics, building reports, or other business functions.

Notes

• Once you have connected to MongoDB and MySQL in PowerShell, you can pipe command results to perform the replication in a single line:

  Select-MongoDB -Connection $mongodb -Table "restaurants" | % { $row = $_ $values = @() $columns | % { $col = $_ $values += $row.$($col) } Add-MySQL -Connection $mysql -Table "restaurants" -Columns $columns -Values $values }

• If you wish to replicate the MongoDB data to another database using another PowerShell module, you will want to exclude the Columns, Connection, and Table columns from the data returned by the Select-MongoDB cmdlet since those columns are used to help pipe data from one CData cmdlet to another:

  $columns = ($data | Get-Member -MemberType NoteProperty | Select-Object -Property Name).Name | ? {$_ -NotIn @('Columns','Connection','Table')}