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Stored Queries

This page discusses managing stored queries in Stardog - the capability to name and store SPARQL queries for future evaluation.

Page Contents
  1. Overview
  2. Storing Queries
  3. Updating Stored Queries
  4. Importing and Exporting Stored Queries
  5. Running Stored Queries
  6. Listing Stored Queries
  7. Removing Stored Queries

Overview

Stardog 4.2 added the capability to name and store SPARQL queries for future evaluation by referring to the query’s name.

Queries of any type can be stored in Stardog and executed directly by using the name of the stored query. Stored queries can be shared with other users, which gives those users the ability to run those queries provided that they have appropriate permissions for a database.

Stored queries can be managed via CLI, Java API, and HTTP API.

Storing Queries

Queries can be stored using the stored add Stardog admin command and specifying a unique name for the stored query:

$ stardog-admin stored add -n types "select distinct ?type {?s a ?type}"

If a file is used to specify the query string without an explicit -n/--name option then the name of the query file is used for the stored query:

$ stardog-admin stored add listProperties.sparql

By default, stored queries can be executed over any database, however, they can be scoped by providing a specific database name with the -d/--database option. Also, by default, only the user who stored the query can access that stored query. Using the --shared flag will allow other users to execute the stored query.

EXAMPLE

The following example stores a shared query with a custom name that can be executed over only the database myDb:

$ stardog-admin stored add --shared -d myDb -n listProperties "select distinct ?p {?s ?p ?o}"

Stored query names must be unique for a Stardog instance. Existing stored queries can be replaced using the --overwrite option in the command.

Updating Stored Queries

Queries can be updated using the --overwrite option on the stored add admin command and specifying an existing name for a stored query:

$ stardog-admin stored add --overwrite -n types "select distinct ?p {?s ?p ?o}"

Importing and Exporting Stored Queries

Stored queries are saved as RDF statements in the Stardog system database and it is possible to export the RDF representation of the queries:

Using the stored-export command:

$ stardog-admin stored export
@prefix system: <http://system.stardog.com/> .

system:QueryExportAll a system:StoredQuery , system:SharedQuery ;
   system:queryName "ExportAll" ;
   system:queryString """construct where {?s ?p ?o}""" ;
   system:queryCreator "admin" ;
   system:queryDatabase "*" .

system:QuerylistDroids a system:StoredQuery , system:ReasoningQuery ;
   system:queryName "listDroids" ;
   system:queryString "select ?x { ?x a :Droid }" ;
   system:queryCreator "luke" ;
   system:queryDatabase "starwars" .

The same RDF representation can be used to import the stored queries as an alternative way of storing new queries or updating existing stored queries.

Using the stored-import command:

$ stardog stored import queries.ttl

In addition to the built-in properties from the system database arbitrary RDF properties can be used for stored queries. The value of these additional annotation properties should be IRIs or literals. Only the values directly linked to the stored query subject in the RDF document will be saved and the triples with a non-stored query subject will be ignored.

Running Stored Queries

Stored queries can be executed using the regular query execution CLI command by passing the name of the stored query:

$ stardog query execute myDb listProperties

Other commands like query explainalso accept stored query names. They can also be passed instead of query string into HTTP API calls.

Listing Stored Queries

To see all the stored queries, use the stored list command:

$ stardog-admin stored list

The results are formatted tabularly:

+--------+-----------------------------------------+
|  Name  |            Query String                 |
+--------+-----------------------------------------+
| graphs | SELECT ?graph (count(*) as ?size)       |
|        | FROM NAMED stardog:context:all          |
|        | WHERE { GRAPH ?graph {?s ?p ?o}}        |
|        | GROUP BY ?graph                         |
|        | ORDER BY desc(?size)                    |
| people | CONSTRUCT WHERE {                       |
|        |    ?person a foaf:Person ;              |
|        |            ?p ?o                        |
|        | }                                       |
| types  | SELECT DISTINCT ?type ?label            |
|        | WHERE {                                 |
|        |    ?s a ?type .                         |
|        |    OPTIONAL { ?type rdfs:label ?label } |
|        | }                                       |
+--------+-----------------------------------------+

3 stored queries

Users can only see the queries they’ve stored and the queries stored by other users that have been --shared. The --verbose option will show more details about the stored queries.

Removing Stored Queries

Stored queries can be removed using the stored remove command:

$ stardog-admin stored remove storedQueryName

If you would like to clear all the stored queries then use the -a/--all option:

$ stardog-admin stored remove -a

Stardog supports a way to use stored queries as subqueries in larger SPARQL queries. For more details see the Stored Query Service section and the blog post of the same name.