SPARQL Reference

This page is the reference for pg_ripple's SPARQL 1.1 query and update engine.

Overview

pg_ripple implements SPARQL 1.1 Query Language and SPARQL 1.1 Update as native PostgreSQL SQL functions. All SPARQL execution is performed inside the extension via the spargebra parser, an algebra optimizer (sparopt), and a translation layer that converts SPARQL algebra to PostgreSQL SQL executed through SPI. Results are decoded back through the dictionary to return RDF terms as text.

Status

SELECT feature_name, status FROM pg_ripple.feature_status()
WHERE feature_name LIKE 'sparql%';

SQL Functions

SPARQL 1.1 Feature Coverage

pg_ripple supports the full SPARQL 1.1 specification:

• SELECT with projection, DISTINCT, REDUCED, LIMIT, OFFSET, ORDER BY
• CONSTRUCT with graph patterns and template triples
• DESCRIBE returning a CBD (Concise Bounded Description)
• ASK returning boolean
• Graph patterns: BGP, OPTIONAL, UNION, MINUS, GRAPH, SERVICE, FILTER, BIND, VALUES
• Property paths: |, /, ^, ?, *, +, !, {n}, {n,}, {n,m}
• Aggregate functions: COUNT, SUM, MIN, MAX, AVG, GROUP_CONCAT, SAMPLE
• Built-in functions: All ~50+ SPARQL 1.1 scalar functions
• Subqueries: nested SELECT patterns
• SPARQL Update: all 10 update forms

RDF-star Support

Triple-quoted patterns <<s p o>> in both subject and object positions are supported. The dictionary stores RDF-star terms as encoded triples (hash of the quoted triple's subject, predicate, and object encoded together).

Performance Notes

• Integer joins: all SPARQL-to-SQL translation encodes bound terms to BIGINT before generating SQL; no string comparisons occur inside VP table queries.
• Filter pushdown: FILTER constants are encoded at translation time.
• Self-join elimination: star patterns on the same subject are collapsed into single-scan plans.
• The plan cache (_pg_ripple.plan_cache) stores compiled SQL for reuse across repeated queries.

Related Pages

• SPARQL Query SQL Reference
• SPARQL Update SQL Reference
• SPARQL Compliance Matrix
• Plan Cache
• Query Optimization
• Feature Status Taxonomy

SPARQL Extension Function IRI Namespace (API-04, v0.91.0)

All pg_ripple SPARQL extension functions are defined under the canonical namespace:

http://pg-ripple.org/fn/

The shorthand pg: prefix maps to this namespace in all SPARQL queries executed through pg_ripple. The prefix is auto-declared — queries do not need to explicitly declare PREFIX pg: <http://pg-ripple.org/fn/>, though doing so is harmless and is the recommended style for queries intended to run against multiple SPARQL endpoints.

Available extension functions

Federation note

Federation partners that wish to invoke pg_ripple extension functions remotely must use the full IRI form, as remote endpoints do not auto-declare the pg: prefix:

FILTER(<http://pg-ripple.org/fn/confidence>(?s, ?p, ?o) > 0.8)