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hetu-core/hetu-docs/en/optimizer/rule-based-optimizations.md

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Rule based optimizations

openLooKeng supports one rule based optimization, described below.

Join Conversion

Inner-join is a mature operation with great efficiency in our newest version. To utilize the advantage, the semi-join queries can be converted to inner-join for better performance.

With rule-based join conversion, openLooKeng automatically converts the semi-join query to inner-join with equal purpose.

The join conversion is governed by the rewrite_filtering_semi_join_to_inner_join session property, with optimizer.rewrite-filtering-semi-join-to-inner-join configuration property providing the default value.

The valid values are:

  • true - enable join conversion
  • false (default) - disable join conversion

Ranking with TopNRankingNumberNode

Ranking operation is optimized with predicate with TopNRankingNumberNode. It boosted the performance greatly on ranking queries.

The TopNRankingNumberNode ranking is governed by the optimize_top_n_ranking_number session property, with optimizer.optimize-top-n-ranking-function configuration property providing the default value.

The valid values are:

  • true (default) - enable ranking with TopNRankingNunmberNode
  • false - disable ranking with TopNRankingNumberNode