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SQL · Query Optimization

What is predicate pushdown?

Hardsql-34
predicate pushdownfilteroptimization

Question

What is predicate pushdown?

Solution

Predicate pushdown means applying filters as early as possible, ideally close to the data source.

Instead of reading:

1 billion rows
↓
filter
↓
10,000 rows

the system tries to read only relevant data:

filter pushed to source
↓
10,000 rows

Example:

SELECT *
FROM sales
WHERE year = 2026;

With a partitioned data source, the engine may read only the relevant year=2026 partitions.

This reduces:

  • Data scanned
  • I/O
  • Network transfer
  • Processing

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