Whenever I index the data, index size is different, even though I set the same config and mapping

whenever I index the data, index size is different even though I set the same config and mapping.
What happen to Elastic Search?

  • tokenizer : standard
  • index compression : true
  • size of index : 2.78G
  • tokenizer : standard
  • index compression : true
  • size of index : 3.00G

3

  • tokenizer : standard
  • index compression : true
  • size of index : 2.89G

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1.

  • tokenizer : standard
  • source compression : true
  • size of index : 3.12G
  • tokenizer : standard
  • source compression : true
  • size of index : 2.76G
  • tokenizer : standard
    -source compression : true
  • size of index : 2.91G