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So far, you've seen how to create a new schema for a Pinot table. In this tutorial, we'll see how to evolve the schema (e.g. add a new column to the schema). This guide assumes you have a Pinot cluster up and running (eg: as mentioned in https://docs.pinot.apache.org/basics/getting-started/running-pinot-locally). We will also assume there's an existing table baseballStats
created as part of the batch quick start.
Pinot only allows adding new columns to the schema. In order to drop a column, change the column name or data type, a new table has to be created.
Let's begin by first fetching the existing schema. We can do this using the controller API:
Let's add a new column at the end of the schema, something like this (by editing baseballStats.schema
In this example, we're adding a new column called yearsOfExperience
with a default value of 1.
You can now update the schema using the following command
Please note: this will not be reflected immediately. You can use the following command to reload the table segments for this column to show up. This can be done as follows:
After the reload, now you can query the new column as shown below:
Real-Time Pinot table: In case of real-time tables, make sure the "pinot.server.instance.reload.consumingSegment" config is set to true inside Server config. Without this, the current consuming segment(s) will not reflect the default null value for newly added columns.
Note that the real values for the newly added columns won't be reflected within the current consuming segment(s). The next consuming segment(s) will start consuming the real values.
New columns can be added with ingestion transforms. If all the source columns for the new column exist in the schema, the transformed values will be generated for the new column instead of filling default values.
As you can observe, the current query returns the defaultNullValue
for the newly added column. In order to populate this column with real values, you will need to re-run the batch ingestion job for the past dates.
Real-Time Pinot table: Backfilling data does not work for real-time tables. If you only have a real-time table, you can convert it to a hybrid table, by adding an offline counterpart that uses the same schema. Then you can backfill the offline table and fill in values for the newly added column. More on hybrid tables here.