Infer Pinot schema from Avro schema

In this recipe, we'll learn how to infer a Pinot schema from an Avro schema.

Pinot Version	1.0.0
Code	startreedata/pinot-recipes/infer-schema-avro-data

Prerequisites

To follow the code examples in this guide, you must install Docker (opens in a new tab) locally and download recipes.

Navigate to recipe

If you haven't already, download recipes.
In the terminal, go to the recipe by running the following command:

cd pinot-recipes/recipes/infer-schema-avro-data

JSON Data

We're going to infer a Pinot schema from the following Avro schema:

{
  "type":"record",
  "namespace":"com.simonaubury",
  "name":"MastodonDetails",
  "fields":[
    {"name":"m_id","type":"long","default":0},
    {"name":"created_at","type": "int","logicalType":"date"},
    {"name":"created_at_str","type":"string","default":"unknown"},
    {"name":"app","type":"string","default":"unknown"},
    {"name":"url","type":"string","default":"null"},
    {"name":"base_url","type":"string","default":"null"},
    {"name":"language","type":"string","default":"null"},
    {"name":"favourites","type":"int","default":0},
    {"name":"username","type":"string","default":""},
    {"name":"bot","type":"boolean"},
    {"name":"tags","type":"int","default":0},
    {"name":"characters","type":"int","default":0},
    {"name":"words","type":"int","default":0},
    {"name":"mastodon_text","type":"string","default":"null"}
  ]
}

/avro/mastodon-topic-value.avsc

Infer schema

Now we're going to infer a schema for this input file. We can do this using the AvroSchemaToPinotSchema command.

You can generate a schema file that creates a dimension column field per Aro field, by running the following command:

docker run \
  -v ${PWD}/config:/config \
  -v ${PWD}/avro:/avro \
  apachepinot/pinot:1.0.0 AvroSchemaToPinotSchema \
  -avroSchemaFile /avro/mastodon-topic-value.avsc \
  -pinotSchemaName="mastodon" \
  -outputDir="/config" \
  -dimensions="" \
  -timeColumnName "created_at" \
  -metrics "favourites,words,characters,tags"

A JSON file will be written to ./config/mastodon.json, the contents of which are shown below:

{
  "schemaName": "mastodon",
  "dimensionFieldSpecs": [
    {"name": "m_id", "dataType": "LONG"},
    {"name": "created_at_str", "dataType": "STRING"},
    {"name": "app", "dataType": "STRING"},
    {"name": "url", "dataType": "STRING"},
    {"name": "base_url", "dataType": "STRING"},
    {"name": "language", "dataType": "STRING"},
    {"name": "username", "dataType": "STRING"},
    {"name": "bot", "dataType": "BOOLEAN"},
    {"name": "mastodon_text", "dataType": "STRING"}
  ],
  "metricFieldSpecs": [
    {"name": "favourites", "dataType": "INT"},
    {"name": "tags", "dataType": "INT"},
    {"name": "characters", "dataType": "INT"},
    {"name": "words", "dataType": "INT"}
  ],
  "dateTimeFieldSpecs": [
    {
      "name": "created_at",
      "dataType": "INT",
      "format": "1:DAYS:EPOCH",
      "granularity": "1:DAYS"
    }
  ]
}

./config/mastodon.json

Merge small segments Infer Pinot schema from JSON data