GH-464 Add log function to SPARQL

qendpoint-store/src/main/java/com/the_qa_company/qendpoint/functions/Log.java

@@ -0,0 +1,63 @@
+package com.the_qa_company.qendpoint.functions;
+
+import com.the_qa_company.qendpoint.store.EndpointStore;
+import org.eclipse.rdf4j.model.Literal;
+import org.eclipse.rdf4j.model.Value;
+import org.eclipse.rdf4j.model.ValueFactory;
+import org.eclipse.rdf4j.model.base.CoreDatatype;
+import org.eclipse.rdf4j.query.algebra.evaluation.ValueExprEvaluationException;
+import org.eclipse.rdf4j.query.algebra.evaluation.function.Function;
+
+public class Log implements Function {
+	@Override
+	public String getURI() {
+		return EndpointStore.BASE_URI + "log";
+	}
+
+	@Override
+	public Value evaluate(ValueFactory valueFactory, Value... args) throws ValueExprEvaluationException {
+		if (args.length < 1 || args.length > 2) {
+			throw new ValueExprEvaluationException(getURI() + "(value, base = 10)");
+		}
+
+		Value valueVal = args[0];
+
+		if (!valueVal.isLiteral() || !(valueVal instanceof Literal lit)) {
+			throw new ValueExprEvaluationException(getURI() + " : value should be a literal");
+		}
+		CoreDatatype cdt = lit.getCoreDatatype();
+
+		if (!cdt.isXSDDatatype() || !cdt.asXSDDatatype().orElseThrow().isNumericDatatype()) {
+			throw new ValueExprEvaluationException(getURI() + " : value should be a numeric literal");
+		}
+
+		double val = lit.doubleValue();
+
+		if (val <= 0) {
+			throw new ValueExprEvaluationException(getURI() + " : value should be a positive number");
+		}
+
+		int base;
+
+		if (args.length >= 2) {
+			Value baseVal = args[1];
+
+			if (!baseVal.isLiteral() || !(baseVal instanceof Literal litb)) {
+				throw new ValueExprEvaluationException(getURI() + " : base should be a literal");
+			}
+			CoreDatatype bcdt = litb.getCoreDatatype();
+
+			if (!bcdt.isXSDDatatype() || !bcdt.asXSDDatatype().orElseThrow().isIntegerDatatype()) {
+				throw new ValueExprEvaluationException(getURI() + " : base should be an int literal");
+			}
+
+			base = litb.intValue();
+		} else {
+			base = 10;
+		}
+		if (base == 10) {
+			return valueFactory.createLiteral(Math.log10(val));
+		}
+		return valueFactory.createLiteral(Math.log(val) / Math.log(base));
+	}
+}

qendpoint-store/src/main/java/com/the_qa_company/qendpoint/store/EndpointStore.java

@@ -18,7 +18,6 @@
 import com.the_qa_company.qendpoint.model.HDTValue;
 import com.the_qa_company.qendpoint.utils.BitArrayDisk;
 import com.the_qa_company.qendpoint.utils.CloseSafeHDT;
-import com.the_qa_company.qendpoint.utils.OverrideHDTOptions;
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.file.PathUtils;
 import org.eclipse.rdf4j.common.concurrent.locks.Lock;
@@ -66,6 +65,10 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 public class EndpointStore extends AbstractNotifyingSail {
+	/**
+	 * base uri
+	 */
+	public static final String BASE_URI = "http://the-qa-company.com/qendpoint/#";
 	/**
 	 * disable the optimizer
 	 */

qendpoint-store/src/main/resources/META-INF/services/org.eclipse.rdf4j.query.algebra.evaluation.function.Function

@@ -1 +1,2 @@
-com.the_qa_company.qendpoint.functions.ParseDateFunction
+com.the_qa_company.qendpoint.functions.ParseDateFunction
+com.the_qa_company.qendpoint.functions.Log

qendpoint-store/src/test/java/com/the_qa_company/qendpoint/functions/LogTest.java

@@ -0,0 +1,49 @@
+package com.the_qa_company.qendpoint.functions;
+
+import com.the_qa_company.qendpoint.store.EndpointStore;
+import org.eclipse.rdf4j.model.Literal;
+import org.eclipse.rdf4j.query.TupleQueryResult;
+import org.eclipse.rdf4j.repository.sail.SailRepository;
+import org.eclipse.rdf4j.repository.util.Repositories;
+import org.eclipse.rdf4j.sail.memory.MemoryStore;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class LogTest {
+	@Test
+	public void funcTest() {
+		MemoryStore ms = new MemoryStore();
+		SailRepository repo = new SailRepository(ms);
+		repo.init();
+		try {
+			Repositories.consumeNoTransaction(repo, conn -> {
+				try (TupleQueryResult res = conn.prepareTupleQuery("""
+						PREFIX qep: <%s>
+
+						SELECT * {
+							VALUES ?number { 10 80 420 10000 20000 1000000 }
+							BIND (qep:log(?number) AS ?logNumberDef)
+							BIND (qep:log(?number, 10) AS ?logNumber10)
+							BIND (qep:log(?number, 16) AS ?logNumber16)
+							BIND (qep:log(?number, 2) AS ?logNumber2)
+						}
+						""".formatted(EndpointStore.BASE_URI)).evaluate()) {
+					res.forEach(bind -> {
+						double value = ((Literal) bind.getValue("number")).doubleValue();
+
+						assertEquals(((Literal) bind.getValue("logNumberDef")).doubleValue(), Math.log10(value), 0.001);
+						assertEquals(((Literal) bind.getValue("logNumber10")).doubleValue(), Math.log10(value), 0.001);
+						assertEquals(((Literal) bind.getValue("logNumber16")).doubleValue(),
+								Math.log10(value) / Math.log10(16), 0.001);
+						assertEquals(((Literal) bind.getValue("logNumber2")).doubleValue(),
+								Math.log10(value) / Math.log10(2), 0.001);
+					});
+				}
+			});
+		} finally {
+			repo.shutDown();
+		}
+	}
+
+}