RegEx query predicates using the | (vertical bar) character cannot use tight index bounds

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    • Type: Improvement
    • Resolution: Unresolved
    • Priority: Major - P3
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    • Affects Version/s: 2.8.0-rc1
    • Component/s: Querying
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    • Query Optimization
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      The mongodb regex parser cannot create accurate bounds to allow indexed lookups when the regex includes the "|" character. This was allowed previously, but could lead to incorrect results.

      Original Description
      I've got a database with 14 mio rows representing an imaginary "file system". There are (amongst others) the fields "type" (only "folder" or "file"), "folder" and "filename".

      I now try this:

      {
type:'folder',
folder:/^example1/
}

Very fast. No results - as expected. In fact, no rows even start with "example".

I now try this:

{
type:'folder',
folder:/^example2/
}

      Very fast, too. No results again - as expected.

      Now, I try this:

      {
type:'folder',
folder:/^example(1|2)/
}

      This query never returns. The whole database becomes horribly slow to the point of being unusable. I cannot even run any other queries. This used to work on 2.4.x. Why?

            Assignee:
            [DO NOT USE] Backlog - Query Optimization
            Reporter:
            rgpublic
            Votes:
            5 Vote for this issue
            Watchers:
            17 Start watching this issue

              Created:
              Updated: