The _id information in a collection entry is really unique?

abernh · August 19, 2021, 8:54pm

This is the function generating your collection documents _ids

agentejo/cockpit/blob/8856aa2cd2ccf1c92bef6374ba238aa02ca080d3/lib/MongoLite/Database.php#L527

    
      
                              $score  += ($matches / $l);
                          }
                      }
                  }
          
          
    }
          
          
    return $score / \count($needles);
          }
          
          
function createMongoDbLikeId() {
          
          
    // use native MongoDB ObjectId if available
              if (class_exists('MongoDB\\BSON\\ObjectId')) {
                  $objId = new \MongoDB\BSON\ObjectId();
                  return (string)$objId;
              }
          
          
    // based on https://gist.github.com/h4cc/9b716dc05869296c1be6
          
          
    $timestamp = \microtime(true);

It uses if available either

  $objId = new \MongoDB\BSON\ObjectId();

(which is what MongoDB normally uses for their _ids https://docs.mongodb.com/manual/core/index-unique/; see also Generating Globally Unique Identifiers for Use with MongoDB | MongoDB Blog )

or a “mongo db like id”, based on

the timestamp in ms
a “random” 5 char integer
a “random” 2-3 char integer

binaried, hashed and hexed.

Both seem to be setup to create a very unique ID in forever UNLESS you generate

MongoDB: > 16million items within 1 second ( https://betterprogramming.pub/is-the-id-property-in-mongodb-100-unique-f1eaa19522ba#dd87 )
MongoLike: > 88million items at the same microsecond (?*)

*) 89000 * 990 ~ 88mill

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The _id information in a collection entry is really unique?

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