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  1. Core Server
  2. SERVER-5503

All capped collections are implicitly limited to 2^31 - 1 documents

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Duplicate
    • 2.0.4, 2.1.0
    • None
    • None
    • None
    • ALL

    Description

      If you attempt to create a capped collection with a maximum number of documents greater than 2^31 - 1, Mongo silently lowers this to exactly 2^31-1:

      > db.runCommand({create: "cappedWithMax", capped: true, size: 10000000, max: 4294967296})
      { "ok" : 1 }
      > db.cappedWithMax.stats().max
      2147483647

      If you leave the "max" field out of the creation command, you still get 2^31 - 1 as max:

      > db.runCommand({create: "cappedWithoutMax", capped: true, size: 10000000})
      { "ok" : 1 }
      > db.cappedWithoutMax.stats().max
      2147483647

      This seems to be due to this section of _userCreateNS in pdfile.cpp (at line 259 on current master):

              if( options["capped"].trueValue() ) {
                  newCapped = true;
                  BSONElement e = options.getField("max");
                  if ( e.isNumber() ) {
                      mx = e.numberInt();
                  }
              }

      I would expect that the range of valid values for max should be either a long (2^63 - 1), unsigned long (2 ^ 64 - 1); or alternately that not specifying max leaves the number of documents unbounded.

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              Unassigned Unassigned
              dcrosta Daniel Crosta
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                Updated:
                Resolved: