Databases Overview

Your production database contains your most important data, and Fivetran’s database connectors are our most important and battle-tested connectors. Our database connectors are designed for correctness and safety. Correctness means that your destination should always be an accurate replica of your database source. Safety means that no matter what, Fivetran should never cause problems in your source database.

Supported databaseslink

Fivetran supports replicating data from the following databases:

• Db2 PRIVATE PREVIEW

• DynamoDB

• MariaDB

• MongoDB

• MySQL

• Oracle

• PostgreSQL

• SAP HANA PRIVATE PREVIEW

• SQL Server

  NOTE: The SAP HANA database connector functions differently from our other database connectors. For more information, see our SAP HANA documentation.

If you’d like to integrate with a database that’s not listed here, please reach out to Fivetran support.

Database Integration Overviewlink

1. Connect: Connect us to your production database or read-replica via a specific Fivetran user that you create in your database. For instructions on creating a Fivetran user, see the setup guide for your database type.
2. Initial sync: Fivetran discovers all selected tables and automatically pulls all historical data for all objects to which it has access. The duration of initial syncs varies by customer, but most syncs finish within a day.
3. Transform and map schema: Fivetran parses through all your data, typecasting and mapping every column in the source object to a column in the corresponding table in the destination. We transform any data types that are not natively supported in the destination into data types that are accepted. Fivetran does not do any aggregations at this stage.
4. Load: Fivetran automatically creates schemas and tables for each mapped source object in the destination. We populate these tables with the data from the initial sync.
5. Incremental updates: Fivetran incrementally updates the data in your destination in batches, using a merge operation (upsert & insert) to only update new or changed data. You can choose how often these batches run, from every 5 minutes to every 24 hours. Fivetran’s unique system automatically recognizes schema changes in your data source and persists these changes to the destination.

Connecting your databaselink

Connection Optionslink

Because our database connectors are pull connectors, Fivetran must have a way to connect to your source database. The three connection strategies that we support are:

• Connect directly to the database port on your database host
• Connect via an SSH tunnel
• Connect via a reverse SSH tunnel

See the Connection Options guide for more details.

Safetylink

Fivetran is a good citizen of your database. You can connect Fivetran to a read-replica of your database if you want to isolate us from your production workloads, but you can also connect us directly to your production instance. Our queries are designed to minimize contention with your production queries in two major ways:

1. Our queries generate simple execution plans that can run concurrently with many other queries.
2. We run our initial sync in a single thread. This means that Fivetran will “compete” relatively weakly for resources and effectively take a low priority if you are running a lot of concurrent queries. This doesn’t mean Fivetran is slow, however; during “quiet” periods, the database will still allocate 100% of its resources to Fivetran’s single thread. During busy periods, though, Fivetran will take a back-seat to your other workloads by design.

Initial synclink

During the initial data sync, Fivetran connects to your source database and copies the entire contents of every table that you’ve selected to sync. The way we perform that initial sync depends on whether your source database has a B-tree (for example, MySQL or SQL Server) or a heap (for example, Postgres or Oracle) data structure.

NOTE: The SAP HANA database connector has a different initial sync strategy from our other database connectors. For more information, see our SAP HANA initial sync documentation.

B-Tree databaseslink

For B-Tree tables, we perform the initial sync using a series of queries that look like this:

select *
from {table}
where {primary key} > ?
order by {primary key}
limit {page size}

This is an efficient strategy because each table in a B-tree database is intrinsically ordered on the {primary key}. There is no need for a sort by clause in this query, because each table is already in {primary key} order.

Heap databaseslink

For heap databases, the initial sync is more complicated. For small-to-medium tables, we sync the entire table with a single select * query. For large tables, we break the contents into more manageable blocks based on the order in which the data was added to the database. We then sync the blocks in chronological order.

Excluding source datalink

If you don’t want to sync all the data from your source database into your destination, you can easily exclude schemas, tables, or columns from your syncs on your Fivetran dashboard. Alternatively, you can change the permissions of the Fivetran user in your source database and restrict its access to certain tables or schemas.

Check initial sync progresslink

You can monitor the progress of your initial sync using the Logs tab on your Fivetran dashboard. In the Logs tab, you can:

• Check the most recent log record to track the progress of your table imports.

  • All tables marked NOT STARTED have not been imported yet.
  • All tables marked COMPLETED have been imported.

• Check older log records to track your sync progress.

To monitor your initial sync in the Logs tab, follow these steps:

1. Log in to your Fivetran Dashboard.

2. In the top menu, click Logs.

3. Type in “import_progress” and click Apply.

   

4. Click on the log record you’d like to view. In the example below, you can see that some tables have been synced and some tables have not yet been started.

   

Transformation and mapping overviewlink

Similar to Cloud API connections, Fivetran’s database replication product pursues a “sync-all” strategy. This means we sync as many source schemas and tables as possible with as little setup and configuration as possible.

However, unlike Cloud API connections, our database connectors do one-to-one mapping of source schemas and tables to destination schemas and tables. Columns are also mapped one-for-one wherever possible, except when no compatible data type exists in the destination. In that case, we will transform data types that are not supported in the destination into data types that are supported.

Loading schemas and tableslink

Schemas and tableslink

A single database connector can replicate multiple schemas (represented below by the blue connector icon), as well as all of their underlying tables. These schemas are stored in the destination in the same logical schema/table hierarchy as exists in your source database. In the destination, each schema name is prepended with the prefix of your choice.

Mapping name from source to destinationlink

For database connectors, we do minimal name-changing between the source and destination. This allows SQL queries written for the source database to be easily ported to the destination, without having to change the field names in the queries. There are only a few exceptions to this rule:

• Schema names that have the connector name prepended, and

• Schema, table, or column names that violate Fivetran’s naming conventions. In these cases, we apply the following rules in the order in which they are listed:

  • Non-ASCII characters (such as Chinese characters) are replaced with a transliteration.
  • We only allow letters, numbers, and underscores. Any other character is replaced with an underscore.
  • Upper-case letters are converted to lower-case.
  • A name that starts with a number gets an underscore prepended to it.
  • The character limit for names is 127 characters. Any name with more than 127 characters is truncated to the limit.

Changing the destination schema namelink

We do not support changing the connector name. It is therefore not possible to change the name of the destination schemas.

If you want to change the name of your destination schema, you can set up a new connector and remove your old connector once the new one has finished syncing. You can also create a SQL view on top of the existing schema with a new name that works better for your BI or SQL layer.

Incremental updateslink

After the initial sync of your historical data, Fivetran moves to performing incremental updates of any new or modified data from your source database. During incremental syncs, we use your database’s native change capture mechanism to request only the data that has changed since our last sync, including deletes. Each database uses a different change capture mechanism:

• DynamoDB Streams (DynamoDB)
• Change Data Capture (MariaDB)
• Change streams (MongoDB)
• Binary logs (MySQL)
• LogMiner (Oracle)
• Logical replication or XMIN system column (PostgreSQL)
• Change tracking or change data capture (SQL Server)
• Shadow tables and triggers (SAP HANA)

During incremental syncs, Fivetran maintains an internal set of progress cursors which allow us to track the exact point where our last successful sync left off. We record the last sync for each row in a column called fivetran_synced (UTC timestamp). This provides a seamless hand-off between syncs, ensuring that we do not miss any data.

Because of our progress cursors, Fivetran’s system is extremely tolerant to service interruptions. If there is an interruption in your service (such as your destination going down), Fivetran will automatically resume syncing exactly where it left off once the issue is resolved, even days or weeks after, as long as log data is still present.

Deleted datalink

All database connectors support syncing deleted data. For tables with primary keys, we mark deleted rows as deleted in your destination, but do not actually remove them. We create an extra column in the destination to mark deleted rows, “_fivetran_deleted” (boolean). Deleted rows will have a true value in this column.

Three databases - MySQL, Oracle, and PostgreSQL - support tables without primary keys. The way we treat deleted rows in these tables varies by connector. See each database connector page for more information.

Frequency of updateslink

By default, all database connectors sync new and modified data every 15 minutes. Depending on the size of each update or the number of tables, syncs may take longer than that. In that case, the next data sync will start at the next 15 minute interval. For example:

1. Update X Start: 9:00am

2. Update X Finish: 9:18am

3. Update Y Start: 9:30am

You can change the update interval in your Fivetran dashboard. When database syncs encounter repeated errors, our system automatically retries the sync after the update interval or one hour, whichever is shorter.

Migrating service providerslink

If you migrate from one database service provider to another, we will need to do a full re-sync. That’s because when you switch to another provider, Fivetran can’t keep track of where our last sync left off, as the new service provider won’t retain the same progress cursor and change log information as the previous provider. Examples of switching service providers include:

• MySQL (Self-Hosted) <–> MySQL RDS
• Postgres (Self-Hosted) <–> Postgres RDS
• SQL Server (Self-Hosted) <–> SQL Server RDS

See the individual database guides for specific instructions on how to migrate.

Automatic re-synclink

Under certain circumstances, Fivetran automatically performs a full table re-sync or a full source re-sync of your source database. The specific circumstances vary by database type.

IMPORTANT: The full table or full source re-sync automatically occurs at your next scheduled sync time. For example, let’s say that your connector syncs every day at 2pm and you make database updates that necessitate a re-sync at 4pm. We schedule your automatic re-sync for 2pm the next day.

Unsupported operationslink

Fivetran’s database connectors deliberately do not support some operations.

Non-primary replicas in SQL Serverlink

In SQL Server, you cannot connect Fivetran to a non-primary replica if you use Change Tracking (CT) as your incremental update mechanism. We can only sync with the primary replica in an availability group, because Microsoft does not allow CT to be enabled on any replica that is not designated as primary.

Restoring from a daily backuplink

You cannot connect Fivetran to a database source that is restored periodically (for example, every night or every hour) from a backup of another database. Restoring the source database from a backup causes Fivetran to perform a complete re-sync, which may never complete if you perform a restore every day.

Data warehouses as sourceslink

You cannot connect Fivetran to a data warehouse like Teradata, Netezza, or Vertica as a source, because these databases have no change capture mechanism. Instead, connect us to whatever source databases are feeding these warehouses.

If you use a regular OLTP database like Postgres or Oracle as a data warehouse, you can connect it to Fivetran as a source. However, your Fivetran syncs may be unacceptably slow if you are populating this data warehouse by periodically truncating and re-creating tables. Be sure to test this issue during your evaluation of Fivetran to make sure you get acceptable performance.

Must allow initial syncs to run without interruptionlink

You cannot run initial syncs within a limited time window (for example, only allow Fivetran to sync from midnight to 8 a.m.). Time limits increase the likelihood that our connection will be interrupted and the sync will need to restart. There is no need to restrict our syncs to off-times; our initial sync queries are designed to be easy for your query planner to schedule around, so the impact on your production workload should be minimal.

Guaranteed initial sync completion dateslink

Fivetran cannot guarantee a completion date for your initial sync. While Fivetran works hard to make your initial sync as fast as possible, the duration of this process is different for every customer.

Skipping historical syncslink

You cannot skip your historical sync.

Starting historical syncs from a specific datelink

You cannot start your historical sync from a specific date (for example, only sync data from August 2014 forward).

One-time production data migrationslink

Fivetran does not support one-time migrations of production data.