Query 6: Using a secondary index with an index predicate

Fetch the name, ticket number, and arrival date of passengers whose arrival date is greater than a given value.

SELECT fullName, bag.ticketNo, bag.bagInfo[].bagArrivalDate
FROM BaggageInfo bag WHERE EXISTS
bag.bagInfo[$element.bagArrivalDate >="2019-01-01T00:00:00"]

Plan:

{
  "iterator kind" : "RECEIVE",
  "distribution kind" : "ALL_SHARDS",
  "distinct by fields at positions" : [ 1 ],
  "input iterator" :
  {
    "iterator kind" : "SELECT",
    "FROM" :
    {
      "iterator kind" : "TABLE",
      "target table" : "BaggageInfo",
      "row variable" : "$$bag",
      "index used" : "simpleindex_arrival",
      "covering index" : false,
      "index row variable" : "$$bag_idx",
      "index scans" : [
        {
          "equality conditions" : {},
          "range conditions" : {}
        }
      ],
      "index filtering predicate" :
      {
        "iterator kind" : "GREATER_OR_EQUAL",
        "left operand" :
        {
          "iterator kind" : "FIELD_STEP",
          "field name" : "bagInfo[].bagArrivalDate",
          "input iterator" :
          {
            "iterator kind" : "VAR_REF",
            "variable" : "$$bag_idx"
          }
        },
        "right operand" :
        {
          "iterator kind" : "CONST",
          "value" : "2019-01-01T00:00:00"
        }
      }
    },
    "FROM variable" : "$$bag",
    "SELECT expressions" : [
      {
        "field name" : "fullName",
        "field expression" :
        {
          "iterator kind" : "FIELD_STEP",
          "field name" : "fullName",
          "input iterator" :
          {
            "iterator kind" : "VAR_REF",
            "variable" : "$$bag"
          }
        }
      },
      {
        "field name" : "ticketNo",
        "field expression" :
        {
          "iterator kind" : "FIELD_STEP",
          "field name" : "ticketNo",
          "input iterator" :
          {
            "iterator kind" : "VAR_REF",
            "variable" : "$$bag"
          }
        }
      },
      {
        "field name" : "bagArrivalDate",
        "field expression" :
        {
          "iterator kind" : "ARRAY_CONSTRUCTOR",
          "conditional" : true,
          "input iterators" : [
            {
              "iterator kind" : "FIELD_STEP",
              "field name" : "bagArrivalDate",
              "input iterator" :
              {
                "iterator kind" : "ARRAY_FILTER",
                "input iterator" :
                {
                  "iterator kind" : "FIELD_STEP",
                  "field name" : "bagInfo",
                  "input iterator" :
                  {
                    "iterator kind" : "VAR_REF",
                    "variable" : "$$bag"
                  }
                }
              }
            }
          ]
        }
      }
    ]
  }
}

Explanation:

• The root iterator of this query plan is a RECEIVE iterator with a single child (input iterator) that is a SELECT iterator.

• The value of the FROM field is an iterator; in this case, it is a TABLE iterator.

• The EXISTS condition is actually converted to a filtering predicate. There is one filtering predicate which is the whole WHERE expression. The index simpleindex_arrival is the only one applicable here and is used.

• The index filtering predicate evaluates the filter criteria on the bagArrivalDate field. Using the greater than and less than operators the filter condition is evaluated.

• The FROM variable is the name of a variable ranging over the records produced by the FROM iterator. Here the FROM iterator is a TABLE iterator, and the FROM variable ($$bag)is the same as the row variable of the TABLE iterator, as the index used is not covering.

• In the SELECT expression three fields (fullname, ticketNo,bag.bagInfo[].bagArrivalDat) are fetched. These correspond to three field names and field expressions in the SELECT expression clause. For the first two fields, the field expression is computed using FIELD_STEP iterator. For the last field, an ARRAY_CONSTRUCTOR iterator is used which iterates over the corresponding arrays to fetch the field value.