Profiling Module

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This XQuery Module contains various functions to test and profile code, and to dump information to standard output.

Conventions[edit]

All functions and errors in this module are assigned to the http://basex.org/modules/prof namespace, which is statically bound to the prof prefix.

Performance Functions[edit]

prof:track[edit]

Signature
prof:track(
  $input   as item()*,
  $options as map(*)?  := map { }
) as item()*
Summary Measures the execution time and memory consumption required for evaluating the specified $input and returns a map with the results. The following $options are available:
  • time: Include execution time in result as xs:decimal (unit: milliseconds; default: true).
  • memory: Include memory consumption in result as xs:integer (unit: bytes; default: false).
  • value: Include value in result (default: true).

Helpful notes:

  • If you are not interested in some of the returned results, you should disable them to save time and memory.
  • Profiling might change the execution behavior of your code: An expression that might be executed iteratively will be cached by the profiling function.
  • If a value has a compact internal representation, memory consumption will be very low, even if the serialized result may consume much more memory.
  • Please note that memory profiling is only approximative, so it can be quite misleading. If the memory option is enabled, main-memory will be garbage-collected before and after evaluation to improve the quality of the measurement.
Properties The function is nondeterministic: evaluation order will be preserved by the compiler.
Examples
  • Return a human-readable representation of the memory consumption caused by fetching an XML document. fetch:doc is used, as fn:doc may already be evaluated at compilation time:
prof:track(fetch:doc('factbook.xml'))?memory
=> prof:human()
  • The function call prof:track((1 to 1000000)[. mod 2 = 0], map { 'time': false() }) will return something similar to:
map {
  "memory": 21548400,
  "value": (2, 4, 6, 8, 10, ...)
}

prof:time[edit]

Signature
prof:time(
  $input  as item(),
  $label  as xs:string?  := ()
) as item()*
Summary Measures the time needed to evaluate $input and outputs a string to standard error or, if the GUI is used, to the Info View. An optional $label may be specified to tag the profiling result. See prof:track for further notes.
Properties The function is nondeterministic: evaluation order will be preserved by the compiler.
Examples
  • prof:time(prof:sleep(1000)) outputs something similar to 1000.99 ms.

prof:memory[edit]

Signature
prof:memory(
  $input  as item(),
  $label  as xs:string?  := ()
) as item()*
Summary Measures the memory allocated by evaluating $input and outputs a string to standard error or, if the GUI is used, to the Info View. An optional $label may be specified to tag the profiling result. See prof:track for further notes.
Properties The function is nondeterministic: evaluation order will be preserved by the compiler.
Examples
  • prof:memory((1 to 100000) ! <a/>) will output something similar to 5620 kB.

prof:current-ms[edit]

Signature
prof:current-ms() as xs:integer
Summary Returns the number of milliseconds passed since 1970/01/01 UTC. The granularity of the value depends on the underlying operating system and may be larger. For example, many operating systems measure time in units of tens of milliseconds.
Properties In contrast to fn:current-time(), the function is nondeterministic and returns different values every time it is called. Its evaluation order will be preserved by the compiler.
Examples
  • convert:integer-to-dateTime(prof:current-ms()) returns the current miliseconds in the xs:dateTime format.

prof:current-ns[edit]

Signature
prof:current-ns() as xs:integer
Summary Returns the current value of the most precise available system timer in nanoseconds.
Properties In contrast to fn:current-time(), the function is nondeterministic and returns different values every time it is called. Its evaluation order will be preserved by the compiler.
Examples Measures the time of an expression:
let $ns1 := prof:current-ns()
return (
  (: process to measure :)
  (1 to 1000000)[. = 0],
  let $ns2 := prof:current-ns()
  let $ms := ((($ns2 - $ns1) idiv 10000) div 100)
  return $ms || ' ms'
)

Debugging Functions[edit]

prof:dump[edit]

Signature
prof:dump(
  $input  as item()*,
  $label  as xs:string?  := ()
) as empty-sequence()
Summary Dumps a serialized representation of $input to STDERR, optionally prefixed with $label, and returns an empty sequence. If the GUI is used, the dumped result is shown in the Info View.
Properties In contrast to fn:trace(), the consumed expression will not be passed on.

prof:variables[edit]

Signature
prof:variables() as empty-sequence()
Summary Prints a list of all current local and global variable assignments to standard error or, if the GUI is used, to the Info View.
As every query is optimized before being evaluated, not all of the original variables may be visible in the output. Moreover, many variables of function calls will disappear because functions are inlined. Function inlining can be turned off by setting INLINELIMIT to 0.
Properties The function is nondeterministic: evaluation order will be preserved by the compiler.
Examples
  • for $x in 1 to 2 return ($x, prof:variables()) will dump the values of $x to standard error.

prof:type[edit]

Signature
prof:type(
  $expr  as item()*
) as item()*
Summary Similar to fn:trace($expr, $msg), but instead of a user-defined message, it emits the compile-time type and estimated result size of its argument.

prof:gc[edit]

Signature
prof:gc(
  $count  as xs:integer  := ()
) as empty-sequence()
Summary Enforces Java garbage collection. If no $count is supplied, garbage will be collected once. Please note that this function should only be used for debugging purposes; in productive code, it is best to trust the garbage collecting strategies of Java.

prof:runtime[edit]

Signature
prof:runtime(
  $option  as xs:string
) as xs:integer
Summary Returns the value of the specified runtime $option. The following options are available:
  • max: Maximum memory that the Java virtual machine will attempt to use.
  • total: Total memory in the Java virtual machine (varies over time).
  • used: Currently used memory (varies over time, will shrink after garbage collection).
  • processors: number of processors available to the Java virtual machine.
option The specified option is unknown.
Examples
  • prof:gc(3), prof:human(prof:runtime('used')) performs some garbage collection and returns the currently used amount of memory in a user-friendly format.

Helper Functions[edit]

prof:void[edit]

Signature
prof:void(
  $input  as item()*
) as empty-sequence()
Summary Absorbs the specified $input and returns an empty sequence. This function is helpful if some (often nondeterministic or side-effecting) code needs to be evaluated and if the resulting value is not required.
Properties The function is nondeterministic: evaluation order will be preserved by the compiler.
Examples

prof:sleep[edit]

Signature
prof:sleep(
  $ms  as xs:integer
) as empty-sequence()
Summary Sleeps for the specified number of milliseconds.
Properties The function is nondeterministic: evaluation order will be preserved by the compiler.

prof:human[edit]

Signature
prof:human(
  $number  as xs:integer
) as xs:string
Summary Returns a human-readable representation of the specified $number.
Example
  • prof:human(16384) returns 16K.

Errors[edit]

Code Description
option The specified option is unknown.

Changelog[edit]

Version 9.2
Version 9.0
Version 8.5
Version 8.1
Version 7.7
Version 7.6
Version 7.5

This module was introduced with Version 7.3.