opt_estimate catalogue

Jonathan Lewis's picture

This is just a list of the notes I’ve written about the opt_estimate() hint.

  • opt_estimate – using the hint to affect index calculations: index_scan and index_filter
  • opt_estimate 2 – applying the hint to nested loop joins, options: nlj_index_scan and nlj_index_filter
  • opt_estimate 3 – a couple of little-known options for the hint, “group_by” and “having”.
  • opt_estimate 4 – applying the hint at the query block level: particularly useful for CTEs (“with subquery”) and non-mergeable views.
  • opt_estimate 5 – a story of failure: trying to use opt_estimate to push predicates into a union all view.

I have a couple more drafts on the topic awaiting completion, but if you know of any other articles that would be a good addition to the list feel free to reference them in the comments.

 

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