Package com.datastax.astra.client.core.query

Class Projection

java.lang.Object
com.datastax.astra.client.core.query.Projection
public class Projection extends Object
Encode the presence of a field in the result.

  • Constructor Details

    • Projection

      public Projection(String field, boolean present)
      Default constructor.
      Parameters:
      field - field value
      present - tell if field is present

    • Projection

      public Projection(String field, Boolean present, Integer sliceStart, Integer sliceEnd)
      Default constructor.
      Parameters:
      field - field value
      present - tell if field is present
      sliceStart - start of slice (mutually exclusive with 'present')
      sliceEnd - end of slice (mutually exclusive with 'present'), optional

  • Method Details

    • include

      public static Projection[] include(String... field)
      Include a field in the result.
      Parameters:
      field - include field
      Returns:
      name to include

    • slice

      public static Projection slice(String field, Integer start, Integer end)
      Specifies the number of elements in an array to return in the query result. 
       
 // Return the first two elements
 { $slice: 2 }

 // Return the last two elements
 { $slice: -2 }

 // Skip 4 elements (from 0th index), return the next 2
 { $slice: [4, 2] }

 // Skip backward 4 elements, return next 2 elements (forward)
 { $slice: [-4, 2] }
      Parameters:
      field - field name for slice
      start - start index of slice
      end - end index of slice
      Returns:
      a projection for the slide

    • exclude

      public static Projection[] exclude(String... field)
      Exclude a field in the result.
      Parameters:
      field - field name to exclude
      Returns:
      list of projection