I notice that there isn't a parameter called enable_indexonly (or similar).
ISTM that such a major new feature should be controlled by a planner
method parameter, just as all the existing planner methods are.
This will help us evaluate index only scans in production, and turn
them off if they have negative impacts.
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Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
