High Performance PostgreSQL for Rails

Replacement Values That Are Statistically Similar

The distribution of the data in tables, columns, and indexes all affect query performance.

Query execution plans are determined dynamically on the fly. PostgreSQL uses the estimates and statistics it’s collected to generate alternative query plans and compare them against one another. The query planner then chooses the lowest cost plan that produces the fastest data retrieval. This means the statistical properties of the data itself are part of the plan selection process. For the scrubber, we want to keep these intact so plan selection in the performance database is closer to what you’d see in your production database.

For example, you might make a query change or add an index in the performance ...