PostgreSQL Read Connector

Create New Read Connector

After you have an Ascend Read Connection set up, then you continue to set up the Read Connector in your dataflow.


Figure 1

The first thing on the top is a highlighted box with the POSTGRES connection, with an USE button which you can use to create a Read Connector using this connection.


Figure 2


  • Name (required): The name to identify this connector with.
  • Description (optional): Description of what data this connector will read.

Connector Configuration


Figure 3

  • BROWSE CONNECTION: Click this button (Figure 3) to explore resource and locate assets to ingest. This will give you access to the Postgres Schema in a modal dialog. Select the schema and then the table you want to ingest and press confirm.
  • Table Name (required): The table to ingest data from.
  • Schema Name (required): The schema the above table belongs to.
  • Replication Strategy (required):
    • Full Resync: This will resync the whole PostgreSQL table using a single connection.
    • Full Resync in Parallel: This will resync the whole PostgreSQL table using multiple connections in parallel.
    • Incremental Column: This uses a column from your table (ex. numeric, date/timestamp) and an internal cursor/watermark/last seen value to pull only the latest records. On first run, pulls all records greater than or equal to (>=) the entered value. On subsequent runs, Ascend manages a cursor/watermark of the highest, last seen value, and only pulls any values greater than (>) the cursor/watermark/last seen value. Each pull is stored as one partition.
    • Table Snapshot: This will take a snapshot of the entire PostgreSQL table on each run.
    • Table Snapshot in Parallel: This will take a snapshot of the entire PostgreSQL table on each run, using multiple connections in parallel.
    • Change Data Capture: Subscribe to your Postgres Server to capture all database table changes in real time. The user must be a superuser or has a replication role to use CDC.
      • Replication Slot Name: Replication slot ensures that the master server will retain the WAL logs that are
        needed by the replicas even when they are disconnected from the master.
        In order to create it, an external plugin is required.
        It is suggested to use wal2json. The installation instructions are available here: and many cloud provider's Postgres have this plugin preinstalled.
        In order to quickly create a slot, run a SQL command in Postgres such as:
SELECT pg_create_logical_replication_slot('ascend_io_slot_1', 'wal2json');


For more information about replication strategies, please refer to our document about Database Read Strategies

Generate Schema


Figure 4

Once you click on the GENERATE SCHEMA button, which is an obligatory step, the data preview will be populated with the schema as in the image above. (Figure 4)

  • Add schema column: Add a custom column to the generated schema

Refresh Schedule

The refresh schedule specifies how often Ascend checks the data location to see if there's new data. Ascend will automatically kick off the corresponding big data jobs once new or updated data is discovered.

Component Pausing

Update the status of the read connector by marking it either Running to mark it active or Paused to pause the connector from running.


Figure 5

Processing Priority (optional)

When resources are constrained, Processing Priority will be used to determine which components to schedule first.


Figure 6

Higher priority numbers are scheduled before lower ones. Increasing the priority on a component also causes all its upstream components to be prioritized higher. Negative priorities can be used to postpone work until excess capacity becomes available.