The Ultimate Guide to High Availability with MariaDB

Rowid Filtering Optimization

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Rowid filtering is an optimization in MariaDB 10.4. Its target use case is as follows:

  • a table uses ref access on index IDX1
  • but it also has a fairly restrictive range predicate on another index IDX2.

In this case, it is advantageous to:

  • Do an index-only scan on index IDX2 and collect rowids of index records into a data structure that allows filtering (let's call it $FILTER).
  • When doing ref access on IDX1, check $FILTER before reading the full record

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