Restrictions on Secondary Indexes

This topic lists and describes the restrictions on secondary indexes. It is important for you to understand the type, size, field definition, option, and index use restrictions when defining and using secondary indexes.

Type Restrictions
  • Indexed fields must contain scalar types.

    Scalar types include integer, character, boolean, string, and byte. See Data Types and Secondary Index Fields for the complete list of types.
  • Indexed fields cannot contain nested documents.

    An indexed field can be a subfield of a nested document, provided the subfield contains scalar types.
  • Indexed fields cannot contain arrays.

Size Restrictions
  • The maximum size of all indexed fields in an index is 32 KB.

    If the collective size exceeds 32 KB, then an insert of the corresponding document results in an encoding error (INDEX_ROW_KEY_ENCODER_ERROR_ENCODING_IS_TOO_LONG).
  • The maximum number of indexes that you can create on a JSON table is 32.

Field Definition Restrictions
  • You cannot specify individual array elements as indexed fields.

  • You cannot specify a table's _id field as an indexed field.

  • You can include a specific field only once as either an indexed or included field, except if you cast the field to different types.

    For example:

    • You can create an index in which the score field is an indexed field cast as a double type, and score is also an included field.

      The included field retains the original data type of the score field.
      maprcli table index add -path /castTable \
         -index castIdx1 \
         -indexedfields '$CAST(score@DOUBLE)' \
         -includedFields score
    • You can create an index in which the score field is an indexed field, cast as a double type, and the score field is also another indexed field, cast as a long type.

      maprcli table index add -path /castTable \
         -index castIdx2 \
         -indexedfields '$CAST(score@DOUBLE)','$CAST(score@LONG)'
  • You cannot use casts with included fields.

  • You cannot specify a field as either an indexed or included field if the field is also specified as a column family JSON path name.

    For example, suppose you have the following JSON table:
    {
         "_id" : "ID",
         "a" :
              {
                   "b" : 
                        {
                             "c" : "value",
                             "d" : "value"
                        },
                   "e" : "value"
              }
    }
    If you create a column family at field c in the JSON path a.b.c, you cannot define field a.b.c as either an indexed or included field. You can define the fields a, a.b, and a.b.d as either indexed or included fields.
  • You cannot specify an included field in which the data in the field spans more than one column family.

    In the following example, the included field sl1.sl2 spans column families, cf2 and cf3:
    maprcli table cf list -path /cftab
    compressionperm  readperm  traverseperm  jsonfamilypath   writeperm  minversions  maxversions  compression  ttl         inmemory  cfname   memoryperm
    u:root           u:root    u:root                         u:root     0            1            lz4          2147483647  false     default  u:root
    u:root           u:root    u:root        sl1              u:root     0            1            lz4          2147483647  false     cf1      u:root
    u:root           u:root    u:root        sl1.sl2.sl3      u:root     0            1            lz4          2147483647  false     cf2      u:root
    u:root           u:root    u:root        sl1.sl2.sl3.sl4  u:root     0            1            lz4          2147483647  false     cf3      u:root
                                     
    maprcli table index add -path /cftab -index i1 -indexedfields sl1.sl2.sl3.sl4.l4a, sl1.l1a -includedfields sl1.sl2,sl1.sl2.sl3.sl4.sl5.l5b -json
    {
            "timestamp":1507419777919,
            "timeofday":"2017-10-07 04:42:57.919 GMT-0700 PM",
            "status":"ERROR",
            "errors":[
                    {
                            "id":22,
                            "desc":"Data for included field sl1.sl2 may not span more than one column family."
                    }
             ]
    }
Option Restrictions
  • Because indexes are automatically split, you cannot disable splits when you create your index.

Index Use Restrictions
  • Indexes optimize filter conditions if you compare indexed fields against scalar values, and the field and scalar value have comparable types.

  • Indexes do not optimize non-existence filter conditions.