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  1. Core Server
  2. SERVER-31360

MatchExpression::getOptimizer() for $or/$and should collapse equivalent clauses

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Details

    • Improvement
    • Status: Backlog
    • Minor - P4
    • Resolution: Unresolved
    • 3.4.9
    • None
    • Querying
    • Query Optimization

    Description

      The `$or` operator produces suboptimal results if the parameters in the list are exactly the same, at least when they're empty: `db.collection.count({$or: [ {}, {} ] })`

      The way I see it the query planner should be able to see that the parameters are exactly the same and simplify that.

      The query `db.collection.count({$or: [ {} ] })` produces a single COUNT stage whereas the more complex query with two empty params creates a SUBPLAN that uses COLLSCAN and only then is able to COUNT so the query is a lot slower.

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          is related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-31639 Additional optimizations for MatchExpression::getOptimizer()

          • Major - P3 - Major loss of function.
          • Closed

          Task - A task that needs to be done. SERVER-75079 Simplify boolean expressions before feeding them to the optimizer

          • Major - P3 - Major loss of function.
          • In Code Review

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-22857 eliminate redundant conditions/clauses from query

          • Major - P3 - Major loss of function.
          • Backlog

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-49274 Coalesce scans of the same index in plans for rooted ORs

          • Major - P3 - Major loss of function.
          • Backlog
          related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-60373 Duplicate predicates in query plan for time-series collection

          • Minor - P4 - Minor loss of function, or other problem where easy workaround is present.
          • Closed

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              backlog-query-optimization Backlog - Query Optimization
              petazz Oskari Petas
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              Dates

                Created:
                Updated: