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Data aggregation

As explained in Machine Learning System Design

The process of combining records into summarized groups according to selected dimensions and time periods.

Data aggregation combines raw records into usable summaries for downstream forecasting and feature calculation. In a retail pipeline, transactions are aggregated daily before other data sources are joined. section 6.7.1

A practical aggregation workflow should:

  • Check transactions, stock, and promotion data for missing or duplicated values before aggregation. section 6.7.1
  • Add each newly aggregated daily partition to the transaction-aggregate table. section 6.7.1
  • Optionally rewrite the previous two or three days to repair duplicates, incomplete data, or corruptions. section 6.7.1
  • Join internal and external data by date, product ID, or store ID, then calculate features. section 6.7.1

Retail forecasting pipeline

A retailer aggregates transaction history daily, joins it with stock, promotions, weather, product, store, and competitor-price data, and derives forecasting features. Gaps in competitor coverage require explicit handling. section 6.7.1

How Machine Learning System Design covers it

How deep it goes
Explains partition updates, optional backfills, quality checks, and joins, but does not specify aggregation formulas.
Examples
Uses daily retail transactions combined with stock, promotions, weather, product, store, and competitor-price records.
What it assumes
Assumes collected historical datasets and existing ETL processes, while emphasizing preprocessing for missing or duplicated records.
What you can do after
Operate a daily aggregation pipeline with validation, corrective rewrites, source joins, and feature calculation.
How it connects
Connects data quality, ETL, forecasting, feature engineering, partitioning, and data integration.

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This explainer was generated by Manning's knowledge graph from the text of Machine Learning System Design. The section links point to the parts of the book it draws on.