pushdown.md

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Query pushdown

Query pushdown is the method of optimizing a query by reducing the amount of data read and processed. It saves memory space, network bandwidth, and reduces the query execution time by moving some parts of the query execution closer to the data source.

Initially FerretDB retrieved all data related to queried collection, and applies filters on its own, making it possible to implement complex logic safely and quickly. To make this process more efficient, we minimize the amount of incoming data, by applying WHERE clause on SQL queries.

:::info You can learn more about query pushdown in our blog post. :::

Supported types and operators

The following table shows all operators and types that FerretDB pushdowns on PostgreSQL backend. If filter uses type and operator, that's marked as pushdown-supported on this list, FerretDB will prefetch less data, resulting with more performent query.

If your application requires better performance for specific operation, feel free to share this with us in our community!

:::tip As query pushdown allows developers to implement query optimizations separately from the features, the table will be updated frequently. :::

	Object	Array	Double	String	Binary	ObjectID	Boolean	Date	Null	Regex	Integer	Timestamp	Long
=	✖️	✖️	⚠️ [1]	✅	✖️	✅	✅	✅	✖️	✖️	✅	✖️	⚠️ [1]
$eq	✖️	✖️	⚠️ [1]	✅	✖️	✅	✅	✅	✖️	✖️	✅	✖️	⚠️ [1]
$gt	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️
$gte	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️
$lt	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️
$lte	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️
$in	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️
$ne	✖️	✖️	⚠️ [1]	✅	✖️	✅	✅	✅	✖️	✖️	✅	✖️	⚠️ [1]
$nin	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️	✖️

[1] {#1}

Numbers outside the range of the safe IEEE 754 precision (< -9007199254740991.0, 9007199254740991.0 >), will prefetch all numbers larger/smaller than max/min value of the range.