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FILTER

Short Description

Operation accepting a set of rows, eliminates some of them, and returns the rest.

Detailed Description​

Filtering the result sets based on predicates is a standard thing for all SQL platforms. This ensures that only relevant data is passed onto the next execution step.

Aim to minimise 'throw-away' rows. For example if a filter is eliminating 99% of rows retrieved within a nested loop which occurs 7000 times, a lot of data is being discarded with no benefit. Re-writing your query to reduce the discarded rows will add speed through reading less data.

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