Avoid queries with unrestricted predicates: Tracker SPARQL Library Reference Manual

## Avoid queries with unrestricted predicates

Queries with unrestricted predicates are those like:

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    SELECT ?p { <a> ?p 42 }

They involve lookups across all possible triples of an object, which roughly translates to a traversal through all tables and columns.

The most pathological case is:

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    SELECT ?s ?p ?o { ?s ?p ?o }

Which does retrieve every triple existing in the store.

Queries with unrestricted predicates are most useful to introspect resources, or the triple store in its entirety. Production code should do this in rare occasions.