This page provides you with instructions on how to extract data from Google Cloud SQL and load it into PostgreSQL. (If this manual process sounds onerous, check out Stitch, which can do all the heavy lifting for you in just a few clicks.)
What is Google Cloud SQL?
Google Cloud SQL is a managed database service that lets DBAs set up, maintain, and administer MySQL and PostgreSQL databases on Google Cloud Platform.
What is PostgreSQL?
PostgreSQL, sometimes referred to as Postgres, calls itself "the world's most advanced open source database." The popular object-relational database management system (ORDBMS) offers enterprise-grade features with a strong emphasis on extensibility and standards compliance.
PostgreSQL runs on all major operating systems, including Linux, Unix, and Windows. It's open source, ACID-compliant, and has full support for foreign keys, joins, views, triggers, and stored procedures in multiple languages. PostgreSQL is often employed as a back-end database for web systems and software tools. It's available in cloud-based deployments by most major cloud vendors. And since its syntax forms the basis for querying Amazon Redshift, which makes migration between the two systems relatively painless, Postgres a good tool for developers who may later use Redshift's data warehouse platform.
Getting data out of Google Cloud SQL
In most cases, the easiest way to retrieve data from relational databases is by writing SQL queries.
Google also provides a REST API for administering databases, instances, and other objects in Cloud SQL. So, for example, to retrieve a resource containing information about a database inside a Cloud SQL instance for a particular project, you could call
If your underlying database is PostgreSQL, you can use the
pg_dump command to export data as a CSV-format flat file or a script that you can run to restore the database on any Postgres server. If your underlying database is MySQL, you can use the
mysqldump command to export entire tables and databases in a format you specify (i.e. delimited text, CSV, or SQL queries that would restore the database).
Sample Google Cloud SQL data
The GET call we mentioned would return a database resource, which contains seven properties. Other API calls return different resources.
For data you export via SQL query, pg_dump, or mysqldump, you need a matching table in your data warehouse to receive the data from Cloud SQL. The information_schema database contains all of the metadata information you need to recreate your tables in another environment.
Preparing Google Cloud SQL data
If you don't already have a data structure in which to store the data you retrieve, you'll have to create a schema for your data tables. Then, for each value in the response, you'll need to identify a predefined datatype (INTEGER, DATETIME, etc.) and build a table that can receive them. Google's documentation should tell you what fields are provided by each endpoint, along with their corresponding datatypes.
Complicating things is the fact that the records retrieved from the source may not always be "flat" – some of the objects may actually be lists. This means you'll likely have to create additional tables to capture the unpredictable cardinality in each record.
Loading data into Postgres
Once you have identified all of the columns you will want to insert, you can use the
CREATE TABLE statement in Postgres to create a table that can receive all of this data. Then, Postgres offers a number of methods for loading in data, and the best method varies depending on the quantity of data you have and the regularity with which you plan to load it.
For simple, day-to-day data insertion, running
INSERT queries against the database directly are the standard SQL method for getting data added. Documentation on INSERT queries and their bretheren can be found in the Postgres documentation here.
For bulk insertions of data, which you will likely want to conduct if you have a high volume of data to load, other tools exist as well. This is where the
COPY command becomes quite useful, as it allows you to load large sets of data into Postgres without needing to run a series of INSERT statements. Documentation can be found here.
The Postgres documentation also provides a helpful overall guide for conducting fast data inserts, populating your database, and avoiding common pitfalls in the process. You can find it here.
Keeping Google Cloud SQL data up to date
At this point you've coded up a script or written a program to get the data you want and successfully moved it into your data warehouse. But how will you load new or updated data? It's not a good idea to replicate all of your data each time you have updated records. That process would be painfully slow and resource-intensive.
Instead, identify key fields that your script can use to bookmark its progression through the data and use to pick up where it left off as it looks for updated data. Auto-incrementing fields such as updated_at or created_at work best for this. When you've built in this functionality, you can set up your script as a cron job or continuous loop to get new data as it appears in Google Cloud SQL.
And remember, as with any code, once you write it, you have to maintain it. If Google modifies its API, or the API sends a field with a datatype your code doesn't recognize, you may have to modify the script. If your users want slightly different information, you definitely will have to.
Other data warehouse options
PostgreSQL is great, but sometimes you need to optimize for different things when you're choosing a data warehouse. Some folks choose to go with Amazon Redshift, Google BigQuery, Snowflake, or Microsoft Azure SQL Data Warehouse, which are RDBMSes that use similar SQL syntax, or Panoply, which works with Redshift instances. Others choose a data lake, like Amazon S3. If you're interested in seeing the relevant steps for loading data into one of these platforms, check out To Redshift, To BigQuery, To Snowflake, To Panoply, To Azure SQL Data Warehouse, and To S3.
Easier and faster alternatives
If all this sounds a bit overwhelming, don’t be alarmed. If you have all the skills necessary to go through this process, chances are building and maintaining a script like this isn’t a very high-leverage use of your time.
Thankfully, products like Stitch were built to move data from Google Cloud SQL to PostgreSQL automatically. With just a few clicks, Stitch starts extracting your Google Cloud SQL data via the API, structuring it in a way that's optimized for analysis, and inserting that data into your PostgreSQL data warehouse.