MarkLogic 10 Product Documentation

op.call

op.call(
   moduleUri as String,
   functionName as String,
   [args as String]
) as expression

Summary

This function to calls a built-in function on every row.

The call() function is needed only for built-in functions that aren't already supported by the Optic expression functions that appear in the Value Processing Functions list.

Use the call() function with care and only for functions that transform values without side effects. Some builtins could adversely affect performance, create deadlocks through the need for update transactions, or worse. The following restrictions apply to the op.call() function:

• Call only built-in functions provided by MarkLogic server. You cannot call SJS or XQY functions using this function. Instead, use a map or reduce function to postprocess the results.
• Do not call update functions, such as xdmp.documentInsert
• Do not call functions that have side effects, such as xdmp.forestClear

Example

// Returns the host name and MarkLogic version.

const op = require('/MarkLogic/optic');

op.fromLiterals([{row:1}])
  .select([
      op.as('hostName', op.call('http://marklogic.com/xdmp', 'host-name')),
      op.as('version',  op.call('http://marklogic.com/xdmp', 'version'))
      ])
  .result();

  

Example

// Concatenates 'EmployeeID' with '_x'.

const op = require('/MarkLogic/optic');

const employees = op.fromView('main', 'employees');

 employees.select(['EmployeeID',
      op.as('concatenated',
             op.call('http://www.w3.org/2005/xpath-functions', 'concat',
                     [op.col("EmployeeID"), "_x"]))
                  ])
	        .result();