# Query logging

Since 4.1.0.

Query logging, disabled by default, prints one-line JSON objects into the standard output.

Its JSON format follows some ElasticSearch conventions and works nicely with the corresponding stack (FileBeat, ES, Kibana).

# Example

  "@timestamp": "2021-02-23T14:02:05.973Z",
  "message": "query:all",
  "application": "ontop-odh",
  "payload": {
    "queryId": "36ade6c6-f091-4af2-9828-ee6316e191f4",
    "classesUsedInQuery": [
    "propertiesUsedInQuery": [
    "tables": [
    "reformulationDuration": 50,
    "reformulationCacheHit": false,
    "httpHeaders": {
      "referer": "http://localhost:8080/"
    "extractedQueryTemplate": {
      "hash": "de167012e1ce3cf9dce66a986a3343d883a1f319f800132565b614498d9c73d8",
      "parameters": {
        "v0": "\"Residence Tuberis\""
    "sparqlQuery": "PREFIX schema: <http://schema.org/>\nSELECT * WHERE {\n  ?h a schema:Hotel ; schema:name ?name .\n  FILTER (langMatches(lang(?name), 'en'))\n  FILTER(str(?name) = \"Residence Tuberis\")\n} \nLIMIT 10",
    "reformulatedQuery": "ans1(h,name)\nCONSTRUCT [h, name] [name/\"Residence Tuberis\"^^@en, h/RDF(http://noi.example.org/data/accommodation/{}(VARCHARToTEXT(Id1m148)),IRI)]\n   NATIVE [Id1m148]\nSELECT v1.\"Id\" AS \"Id1m148\"\nFROM \"v_accommodationsopen\" v1\nWHERE ('Residence Tuberis' = v1.\"AccoDetail-en-Name\" AND 'HotelPension' = v1.\"AccoTypeId\")\nLIMIT 10\n",
    "executionBeforeUnblockingDuration": 8,
    "executionAndFetchingDuration": 30,
    "totalDuration": 80,
    "resultCount": 10

# Entries

Key Type Description
@timestamp Timestamp
message String Type of the message. It always start with the prefix query:. Its default value is query:all. In case of an exception, the value starts with query:exception-.
application String Controlled by the property ontop.applicationName.
payload JSON object Gathers the entries below.
queryId UUID Unique to each query.
classesUsedInQuery Array of IRIs IRIs of the classes appearing in the SPARQL query.
propertiesUsedInQuery Array of IRIs IRIs of the properties appearing in the SPARQL query.
tables Array of Strings Names of the relations appearing in the SQL query.
reformulationDuration Integer Query reformulation duration (in ms).
reformulationCacheHit Boolean True if the reformulated query cache has been used
httpHeaders JSON object Values of a specific list of HTTP headers. By default, this list is empty. To track for instance the referer, set the property ontop.queryLogging.includeHttpHeader.referer to true.
extractedQueryTemplate. hash String Hash of the query template extracted, after removing extracted constants. Can be shared by similar queries.
extractedQueryTemplate. parameters JSON object Constants extracted and replaced by variables.
sparqlQuery String SPARQL query.
reformulatedQuery String Includes the SQL query and the post-processing.
executionBefore UnblockingDuration Integer Duration between the moments where the SQL query is sent and the result set is unblocked (in ms).
executionAndFetching Duration Integer Duration between the moments where the SQL query is sent and the last result is fetched (in ms).
totalDuration Integer Total duration (in ms).
resultCount Integer Number of results returned.

# Default settings

# Query logging is disabled by default
# Application name (needed for logging)
# Includes the SPARQL query string into the query log
# Includes the reformulated query into the query log
# Includes classes and properties into the query log
# Includes DB tables/views into the query log
# Provides separated message at different phases (after reformulation, result set unblocked, last result fetched)
# Sets that merged messages are only inserted when decomposition is disabled