Subsetting/merge using iterators

[dmgaldi]

Overview

• Optimization to have subsetting/merge use Iterator instead of HTTP input streams
• Compute stream is still using HTTP but being adapted to Iterator.

Testing

• Tested various different requests: Mostly this merge:

  {
  "studyId": "VBP_MEGA",
  "derivedVariables": [],
  "filters": [
      {
          "entityId": "EUPATH_0000609",
          "type": "stringSet",
          "variableId": "OBI_0001909",
          "stringSet": [
              "Ixodes scapularis",
              "Ixodidae",
              "Ixodes pacificus",
              "Ixodes ricinus",
              "Dermacentor variabilis",
              "Dermacentor reticulatus",
              "Dermacentor occidentalis"
          ]
      },
      {
          "entityId": "OBI_0000659",
          "type": "dateRange",
          "variableId": "EUPATH_0043256",
          "min": "2002-02-09T00: 00: 00Z",
          "max": "2021-04-30T00: 00: 00Z"
      }
  ],
  "entityId": "GAZ_00000448",
  "outputVariables": [
      {
          "entityId": "GAZ_00000448",
          "variableId": "EUPATH_0043204"
      },
      {
          "entityId": "GAZ_00000448",
          "variableId": "OBI_0001620"
      },
      {
          "entityId": "GAZ_00000448",
          "variableId": "OBI_0001621"
      },
      {
          "entityId": "EUPATH_0000605",
          "variableId": "POPBIO_8000185"
      }
  ]
  }