AQL query statistics

Execution statistics can be retrieved by calling getExtra() on the cursor. The statistics are returned in the return value’s stats attribute:

db._query(`
  FOR i IN 1..@count
    INSERT { _key: CONCAT('anothertest', TO_STRING(i)) } INTO mycollection`,
 { count: 100 },
 {},
 { fullCount: true }
).getExtra();

db._query({
  "query": `
    FOR i IN 200..@count
      INSERT { _key: CONCAT('anothertest', TO_STRING(i)) } INTO mycollection`,
  "bindVars": { count: 300 },
  "options": { fullCount: true }
}).getExtra();

[ArangoCollection 61343, "mycollection" (type document, status loaded)]

{ 
  "warnings" : [ ], 
  "stats" : { 
    "writesExecuted" : 100, 
    "writesIgnored" : 0, 
    "scannedFull" : 0, 
    "scannedIndex" : 0, 
    "cursorsCreated" : 0, 
    "cursorsRearmed" : 0, 
    "cacheHits" : 0, 
    "cacheMisses" : 0, 
    "filtered" : 0, 
    "httpRequests" : 0, 
    "fullCount" : 0, 
    "executionTime" : 0.000794560000031197, 
    "peakMemoryUsage" : 32768 
  } 
}

{ 
  "warnings" : [ ], 
  "stats" : { 
    "writesExecuted" : 101, 
    "writesIgnored" : 0, 
    "scannedFull" : 0, 
    "scannedIndex" : 0, 
    "cursorsCreated" : 0, 
    "cursorsRearmed" : 0, 
    "cacheHits" : 0, 
    "cacheMisses" : 0, 
    "filtered" : 0, 
    "httpRequests" : 0, 
    "fullCount" : 0, 
    "executionTime" : 0.0007774680000238732, 
    "peakMemoryUsage" : 32768 
  } 
}

The meaning of the statistics attributes is as follows:

• writesExecuted: The total number of data-modification operations successfully executed. This is equivalent to the number of documents created, updated, or removed by INSERT, UPDATE, REPLACE, REMOVE, or UPSERT operations.
• writesIgnored: The total number of data-modification operations that were unsuccessful, but have been ignored because of the ignoreErrors query option.
• scannedFull: The total number of documents iterated over when scanning a collection without an index. Documents scanned by subqueries are included in the result, but operations triggered by built-in or user-defined AQL functions are not.
• scannedIndex: The total number of documents iterated over when scanning a collection using an index. Documents scanned by subqueries are included in the result, but operations triggered by built-in or user-defined AQL functions are not.
• cursorsCreated: The total number of cursor objects created during query execution. Cursor objects are created for index lookups.
• cursorsRearmed: The total number of times an existing cursor object was repurposed. Repurposing an existing cursor object is normally more efficient compared to destroying an existing cursor object and creating a new one from scratch.
• cacheHits: The total number of index entries read from in-memory caches for indexes of type edge or persistent. This value is only non-zero when reading from indexes that have an in-memory cache enabled, and when the query allows using the in-memory cache (i.e. using equality lookups on all index attributes).
• cacheMisses: The total number of cache read attempts for index entries that could not be served from in-memory caches for indexes of type edge or persistent. This value is only non-zero when reading from indexes that have an in-memory cache enabled, the query allows using the in-memory cache (i.e. using equality lookups on all index attributes) and the looked up values are not present in the cache.
• filtered: The total number of documents removed after executing a filter condition in a FilterNode or another node that post-filters data. Note that nodes of the IndexNode type can also filter documents by selecting only the required index range from a collection, and the filtered value only indicates how much filtering was done by a post-filter in the IndexNode itself or following FilterNode nodes. Nodes of the EnumerateCollectionNode and TraversalNode types can also apply filter conditions and can report the number of filtered documents.
• httpRequests: The total number of cluster-internal HTTP requests performed.
• fullCount (optional): The total number of documents that matched the search condition if the query’s final top-level LIMIT operation were not present. This attribute may only be returned if the fullCount option was set when starting the query and only contains a sensible value if the query contains a LIMIT operation on the top level.
• executionTime: The query execution time (wall-clock time) in seconds.
• peakMemoryUsage: The maximum memory usage of the query while it was running. In a cluster, the memory accounting is done per shard, and the memory usage reported is the peak memory usage value from the individual shards. Note that to keep things light-weight, the per-query memory usage is tracked on a relatively high level, not including any memory allocator overhead nor any memory used for temporary results calculations (e.g. memory allocated/deallocated inside AQL expressions and function calls).
• nodes (optional): When the query is executed with the option profile set to at least 2, then this value contains runtime statistics per query execution node. For a human readable output you can execute db._profileQuery(<query>, <bind-vars>) in the arangosh.
  • id: The execution node ID to correlate the statistics with the plan returned in the extra attribute.
  • calls: The number of calls to this node.
  • items: The number of items returned by this node. Items are the temporary results returned at this stage.
  • runtime: The execution time of this node in seconds.