xdmp:query-meters

xdmp:query-meters() as element()

Summary

Returns the current value of the resource meters for this query sequence.

Usage Notes

The resource meters returned include:

elapsed-time

The time elapsed since the start of the processing of this query, in the form of a duration.

requests

The number of requests. Request: MarkLogic. Any invocation of a program, whether through an App Server, through a task server, or any other means. In addition, certain client calls to App Servers (for example, loading an XML document through XCC, downloading an image through HTTP, or locking a document through WebDAV) are also requests. The value of requests is normally 1, but can be greater than 1 in some situations such as when error handler is set for the specified app server, or when pre-commit triggers are used for the request.

list-cache-hits

The number of successful list cache lookups. The list cache holds search termlists used to accelerate path expressions and text searches.

list-cache-misses

The number of unsuccessful list cache lookups. Each unsuccessful list cache lookup was followed by a disk access to load the search termlist into the cache.

in-memory-list-hits

The number of successful list lookups in in-memory stands.

list-size

The aggregate size in bytes read from disk by unsuccessful list cache lookups. Each unsuccessful list cache lookup is followed by a disk access to load the search term list into the cache.

expanded-tree-cache-hits

The number of successful expanded tree cache lookups. The expanded tree cache cache holds XML document data in the expanded representation used by the XQuery evaluator.

expanded-tree-cache-misses

The number of unsuccessful expanded tree cache lookups. Each unsuccessful expanded tree lookup was followed by a compressed tree cache lookup to load the expanded tree into the cache.

compressed-tree-cache-hits

The number of successful compressed tree cache lookups. The compressed tree cache holds XML document data in the compressed representation stored on disk.

compressed-tree-cache-misses

The number of unsuccessful compressed tree cache lookups. Each unsuccessful compressed tree cache lookup was followed by a disk access to load the compressed tree into the cache.

in-memory-compressed-tree-hits

The number of successful compressed tree lookups in in-memory stands.

compressed-tree-size

The aggregate size in bytes read from disk by unsuccessful compressed tree cache lookups. Each unsuccessful compressed tree cache lookup is followed by a disk access to load the compressed tree into the cache.

value-cache-hits

The number of successful value cache lookups. The value cache is a transient cache that exists only for the duration of one query. It holds typed values, and is used to accelerate the frequent conversion of nodes to typed values.

value-cache-misses

The number of unsuccessful value cache lookups. Each unsuccessful value cache lookup was followed by a conversion of an XML node to a typed value.

regexp-cache-hits

The number of successful regular expression cache lookups. The regular expression cache is a transient cache that exists only for the duration of one query. It holds compiled regular expressions, and is used to accelerate the frequent use of regular expressions during the evaluation of a query.

regexp-cache-misses

The number of unsuccessful regular expression cache lookups. Each unsuccessful regular expression cache lookup was followed by a compilation of a regular expression from source text.

link-cache-hits

The number of successful link cache lookups. The link cache is a transient cache that exists only for the duration of one query. It holds pointers to expanded trees, and is used to accelerate the frequent dereferencing of link nodes.

link-cache-misses

The number of unsuccessful link cache lookups. Each unsuccessful link cache lookup was followed by a search for the link target tree.

filter-hits

The number of successful search filter matches.

filter-misses

The number of unsuccessful search filter matches.

fragments-added

The number of XML fragments added to the database by an update.

fragments-deleted

The number of XML fragments deleted from the database by an update.

fs-program-cache-hits

The number of module cache hits from the entire program made from modules on the file system.

fs-program-cache-misses

The number of module cache misses from the entire program made from modules on the file system.

db-program-cache-hits

The number of module cache hits from the entire program made from modules in a database (may contain library modules from the special Modules directory).

db-program-cache-misses

The number of module cache misses from the entire program made from modules in a database (may contain library modules from the special Modules directory).

env-program-cache-hits

The number of module cache hits from the entire program made from ad hoc XSLT stylesheet nodes.

env-program-cache-misses

The number of module cache misses from the entire program made from ad hoc XSLT stylesheet nodes.

fs-main-module-sequence-cache-hits

The number of main module cache hits from main modules on the file system.

fs-main-module-sequence-cache-misses

The number of main module cache misses from main modules on the file system.

db-main-module-sequence-cache-hits

The number of main module cache hits from main modules in a database.

db-main-module-sequence-cache-misses

The number of main module cache misses from main modules in a database.

fs-library-module-cache-hits

The number of library module cache hits from library modules on the file system.

fs-library-module-cache-misses

The number of library module cache misses from library modules on the file system.

db-library-module-cache-hits

The number of library module cache hits from library modules from the modules database.

db-library-module-cache-misses

The number of library module cache misses from library modules from the modules database.

read-locks

The number of read locks.

write-locks

The number of write locks.

compile-time

The aggregate time in seconds spent compiling a module or a program.

run-time

The aggregate time in seconds spent evaluating/running a module or a program.

lock-time

The aggregate time in seconds forests spend waiting for transactional read and write locks. This time can exceed the run-time.

contemporaneous-timestamp-time

The time in seconds spent by queries waiting for the contemporaneous timestamp for which any transaction is known to have committed. When the multi-version concurrency control is set contemporaneous, queries can block waiting for the contemporaneous transactions to fully commit.

indexing-time

The indexing time of documents in seconds before they are inserted into the database.

commit-time

The aggregate commit phase time in seconds.

Some meters are broken down by fragment root and document URI:

fragments

A sequence of fragment elements, each containing:

root

The fragment root name.

expanded-tree-cache-hits

A count of successful expanded tree cache lookups for this fragment root.

expanded-tree-cache-misses

A count of unsuccessful expanded tree cache lookups for this fragment root.

documents

A sequence of document elements, each containing:

uri

The document URI.

expanded-tree-cache-hits

A count of successful expanded tree cache lookups for this document URI.

expanded-tree-cache-misses

A count of unsuccessful expanded tree cache lookups for this document URI.

There are also meters that measure the query activity per host. There is a qm:hosts element with one qm:host child per host that participates in the query. Each qm:host element contains meters showing the round-trip-time and round-trip-count for communications between the evaluator host and the host referenced in the xdmp:query-meters output. The qm:hosts element is empty for a single-node cluster.

Certain operations are run concurrently with the timing operations, and if those operations are not actually used in the query, they might not be included in the timings. This occurs for operations like xdmp:estimate , xdmp:exists , and lexicon calls (for example, cts:element-values ). If you want to see the total timings that include calls that are not used, you can form some other expression with the results of the calls. For example, if you have an expression that calls xdmp:estimate in a let expression, you can add 0 to the output, which causes it to be included in the timings (something like xdmp:estimate($query) + 0 ).

Example

  xdmp:query-meters()
  =>
  <qm:query-meters
   xsi:schemaLocation="http://marklogic.com/xdmp/query-meters
       query-meters.xsd"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:qm="http://marklogic.com/xdmp/query-meters">
    <qm:elapsed-time>PT0.22S</qm:elapsed-time>
    <qm:requests>1</qm:requests>
    <qm:list-cache-hits>0</qm:list-cache-hits>
    <qm:list-cache-misses>0</qm:list-cache-misses>
    <qm:list-size>0</qm:list-size>
    <qm:in-memory-list-hits>0</qm:in-memory-list-hits>
    <qm:expanded-tree-cache-hits>0
       </qm:expanded-tree-cache-hits>
    <qm:expanded-tree-cache-misses>0
       </qm:expanded-tree-cache-misses>
    <qm:compressed-tree-cache-hits>0
       </qm:compressed-tree-cache-hits>
    <qm:compressed-tree-cache-misses>0
       </qm:compressed-tree-cache-misses>
    <qm:in-memory-compressed-tree-hits>0
       </qm:in-memory-compressed-tree-hits>
    <qm:compressed-tree-size>0</qm:compressed-tree-size>
    <qm:value-cache-hits>0</qm:value-cache-hits>
    <qm:value-cache-misses>0</qm:value-cache-misses>
    <qm:regexp-cache-hits>0</qm:regexp-cache-hits>
    <qm:regexp-cache-misses>0</qm:regexp-cache-misses>
    <qm:link-cache-hits>0</qm:link-cache-hits>
    <qm:link-cache-misses>0</qm:link-cache-misses>
    <qm:fragments-added>0</qm:fragments-added>
    <qm:fragments-deleted>0</qm:fragments-deleted>
    <qm:fs-program-cache-hits>1</qm:fs-program-cache-hits>
    <qm:fs-program-cache-misses>0</qm:fs-program-cache-misses>
    <qm:db-program-cache-hits>0</qm:db-program-cache-hits>
    <qm:db-program-cache-misses>0</qm:db-program-cache-misses>
    <qm:env-program-cache-hits>0</qm:env-program-cache-hits>
    <qm:env-program-cache-misses>0</qm:env-program-cache-misses>
    <qm:fs-main-module-sequence-cache-hits>0
       </qm:fs-main-module-sequence-cache-hits>
    <qm:fs-main-module-sequence-cache-misses>0
       </qm:fs-main-module-sequence-cache-misses>
    <qm:db-main-module-sequence-cache-hits>0
       </qm:db-main-module-sequence-cache-hits>
    <qm:db-main-module-sequence-cache-misses>0
       </qm:db-main-module-sequence-cache-misses>
    <qm:fs-library-module-cache-hits>0
       </qm:fs-library-module-cache-hits>
    <qm:fs-library-module-cache-misses>0
       </qm:fs-library-module-cache-misses>
    <qm:db-library-module-cache-hits>0
       </qm:db-library-module-cache-hits>
    <qm:db-library-module-cache-misses>0
       </qm:db-library-module-cache-misses>
    <qm:read-locks>0</qm:read-locks>
    <qm:write-locks>0</qm:write-locks>
    <qm:lock-time>0</qm:lock-time>
    <qm:contemporaneous-timestamp-time>0</qm:contemporaneous-timestamp-time>
    <qm:compile-time>0.000375</qm:compile-time>
    <qm:commit-time>0</qm:commit-time>
    <qm:run-time>0</qm:run-time>
    <qm:indexing-time>0</qm:indexing-time>
    <qm:fragments/>
    <qm:documents/>
    <qm:hosts/>
  </qm:query-meters>

Example

xquery version "1.0-ml";
declare namespace qm="http://marklogic.com/xdmp/query-meters";

fn:count(collection()),
xdmp:query-meters()/qm:elapsed-time

=> The count of the number of documents in the database followed by
   the elapsed-time element of the xdmp:query-trace XML output:

153
<qm:elapsed-time xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 xmlns:qm="http://marklogic.com/xdmp/query-meters">
                 PT0.04S</qm:elapsed-time>