To begin, it’s useful to understand how ThirdEye generates queries.

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Understanding ThirdEye query generation

ThirdEye can monitor metrics at any granularity. Consider this alert: 
{
  "name": "example-alert",
  "template": {
    "name": "startree-threshold"
  },
  "templateProperties": {
    "dataSource": "pinotQuickStartLocal",
    "dataset": "order_events",
    "aggregationFunction": "count",
    "aggregationColumn": "customer_id",
    "monitoringGranularity": "PT1H",
    ... # other parameters
  },
  "cron": "0 0 0 1/1 * ? *"
}
example_alert.json monitoringGranularity is PT1H. This means ThirdEye will aggregate data into buckets of 1 hour. monitoringGranularity can be changed to 15 minutes PT15M or daily P1D, ThirdEye will generate the corresponding SQL query. A generated query looks like this: 
SELECT 
  DATETIMECONVERT(<timeColum>, <timeColumnFormat>, 1:MILLISECONDS:EPOCH, <monitoringGranularity> ) as ts,
  COUNT(metric),
FROM order_events
WHERE ...
GROUP BY DATETIMECONVERT(timeColum, <timeColumnFormat>, 1:MILLISECONDS:EPOCH, <monitoringGranularity>)
ORDER BY ts
GROUP BY DATETIMECONVERT(<timeColum>, <timeColumnFormat>, 1:MILLISECONDS:EPOCH, <monitoringGranularity>) means: take the time column, convert it to milliseconds and group by buckets of <monitoringGranularity>. This time transformation can make the query slow, especially when there are a lot of rows in the Pinot table. To avoid this performance hit, you can add a time column that corresponds to the specific
granularity you want to use and configure ThirdEye to use it.

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Setting pre-computed time columns in dataset configurations

Pre-computed time columns are set in the dataset configuration. Your dataset configuration details are found at https://<your.thirdeye.instance.cloud>/configuration/datasets/all. You can click on a dataset there to edit it. Consider this dataset configuration: 
{
  "name": "pageviews",
  "dimensions": [
    "country",
    "browser",
    ...
  ],
  "timeColumn": {
    "name": "pageviewdate",
    "interval": 0.001,
    "format": "SIMPLE_DATE_FORMAT:yyyy-MM-dd",
    "timezone": "UTC"
  },
  "dataSource": {
    "name": "pinot"
  }
}
dataset.json If you know you will often use an hourly monitoringGranularity PT1H:
  1. add a pre-computed time column in your pinot table that correspond to hourly buckets
  2. update the dataset configuration timeColumns metadata: 
    {
  "name": "pageviews",
  "dimensions": [
    "country",
    "browser",
    ...
  ],
  "timeColumn": {
    "name": "pageviewdate",
    "interval": 0.001,
    "format": "SIMPLE_DATE_FORMAT:yyyy-MM-dd",
    "timezone": "UTC"
  },
  "dataSource": {
    "name": "pinot"
  },
  #### ADD THIS #### 
  "timeColumns": [
    {
      "name": "hourlyBuckets",      # the name of the column
      "format": "1:HOURS:EPOCH",    # the Pinot format of the column 
      "granularity": "PT1H"         # the granularity of the buckets - in ISO-8601 format
      "timezone": "UTC"             # the timezone of the buckets
    }
  ]
}
    dataset_with_precomputed_time_column
With this change, when an alert is in timezone UTC and has granularity hourly PT1H, ThirdEye will optimize the query using the hourlyBuckets column. For other configurations, it will use the default time column. You can add as many precomputed time columns as you want. For time format see timeFormat strings.