Maximum Length of a Global Reference

Maximum Length of a Global Reference

The total length of a global reference — that is, the reference to a specific global node or subtree — is limited to 511 encoded characters (which may be fewer than 511 typed characters).

For a conservative determination of the size of a given global reference, use the following guidelines:

1. For the global name: add 1 for each character.

2. For a purely numeric subscript: add 1 for each digit, sign, or decimal point.

3. For a subscript that includes nonnumeric characters: add 3 for each character.

   If a subscript is not purely numeric, the actual length of the subscript varies depending on the character set used to encode the string. A multibyte character can take up to 3 bytes.

   Note that an ASCII character can take up 1 or 2 bytes. If the collation does case folding, an ASCII character can take 1 byte for the character and 1 byte for the disambiguation byte. If the collation does not perform case folding, an ASCII character takes 1 byte.

4. For each subscript, add 1.

If the sum of these numbers is greater than 511, the reference may be too long.

Because of the way that the limitation is determined, if you must have long subscript or global names, it is helpful to avoid a large number of subscript levels. Conversely, if you are using multiple subscript levels, avoid long global names and long subscripts. Because you may not be able to control the character set(s) you are using, it is useful to keep global names and subscripts shorter.

When there are doubts about particular references, it is useful to create test versions of global references that are of equivalent length to the longest expected global reference (or even a little longer). Data from these tests provides guidance on possible revisions to your naming conventions prior to building your application.