Better control over read or write transactions.

core/src/main/java/uk/gov/gchq/magmacore/database/MagmaCoreDatabase.java

@@ -32,10 +32,14 @@
 public interface MagmaCoreDatabase {
 
     /**
-     * Start a transaction in READ mode and which will switch to WRITE if an update is attempted but
-     * only if no intermediate transaction has performed an update.
+     * Start a transaction in READ mode.
      */
-    void begin();
+    void beginRead();
+
+    /**
+     * Start a transaction in Write mode.
+     */
+    void beginWrite();
 
     /**
      * Commit a transaction - Finish the current transaction and make any changes permanent (if a

core/src/main/java/uk/gov/gchq/magmacore/database/MagmaCoreJenaDatabase.java

@@ -31,6 +31,7 @@
 import org.apache.jena.query.QueryFactory;
 import org.apache.jena.query.QuerySolution;
 import org.apache.jena.query.ResultSet;
+import org.apache.jena.query.TxnType;
 import org.apache.jena.rdf.model.Literal;
 import org.apache.jena.rdf.model.Model;
 import org.apache.jena.rdf.model.ModelFactory;
@@ -114,9 +115,21 @@ public void register(final IriBase base) {
      * {@inheritDoc}
      */
     @Override
-    public void begin() {
+    public void beginRead() {
         if (!dataset.isInTransaction()) {
-            dataset.begin();
+            dataset.begin(TxnType.READ);
+        } else {
+            throw new IllegalStateException("Already in a transaction");
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public void beginWrite() {
+        if (!dataset.isInTransaction()) {
+            dataset.begin(TxnType.WRITE);
         } else {
             throw new IllegalStateException("Already in a transaction");
         }
@@ -426,7 +439,7 @@ public final List<Thing> toTopObjects(final QueryResultList queryResultsList) {
      */
     @Override
     public void dump(final PrintStream out) {
-        begin();
+        beginRead();
         final Model model = dataset.getDefaultModel();
         final StmtIterator statements = model.listStatements();
 
@@ -444,7 +457,7 @@ public void dump(final PrintStream out) {
      * @param language RDF language syntax to output data as.
      */
     public final void dump(final PrintStream out, final Lang language) {
-        begin();
+        beginRead();
         RDFDataMgr.write(out, dataset.getDefaultModel(), language);
         abort();
     }
@@ -456,7 +469,7 @@ public final void dump(final PrintStream out, final Lang language) {
      * @param language RDF language syntax to output data as.
      */
     public final void load(final InputStream in, final Lang language) {
-        begin();
+        beginWrite();
         final Model model = dataset.getDefaultModel();
         RDFDataMgr.read(model, in, language);
         commit();

core/src/main/java/uk/gov/gchq/magmacore/database/MagmaCoreRemoteSparqlDatabase.java

@@ -88,9 +88,19 @@ public MagmaCoreRemoteSparqlDatabase(final String serviceUrl, final Dataset data
     /**
      * {@inheritDoc}
      */
-    public final void begin() {
+    public final void beginRead() {
+        if (!connection.isInTransaction()) {
+            connection.begin(TxnType.READ);
+        } else {
+            throw new IllegalStateException("Already in a transaction");
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public final void beginWrite() {
         if (!connection.isInTransaction()) {
-            // The default TxnType.READ_PROMOTE is not supported.
             connection.begin(TxnType.WRITE);
         } else {
             throw new IllegalStateException("Already in a transaction");
@@ -431,7 +441,7 @@ public final void dump(final PrintStream out, final Lang language) {
      * @param language RDF language syntax to output data as.
      */
     public final void load(final InputStream in, final Lang language) {
-        begin();
+        beginWrite();
         final Dataset dataset = connection.fetchDataset();
         final Model model = dataset.getDefaultModel();
         RDFDataMgr.read(model, in, language);

core/src/main/java/uk/gov/gchq/magmacore/service/MagmaCoreService.java

@@ -709,7 +709,7 @@ public Thing get(final IRI iri) {
      */
     public Thing getInTransaction(final IRI iri) {
         try {
-            database.begin();
+            database.beginRead();
             final Thing result = database.get(iri);
             database.commit();
             return result;
@@ -724,9 +724,25 @@ public Thing getInTransaction(final IRI iri) {
      *
      * @param func {@link Function} to run.
      */
-    public void runInTransaction(final Function<MagmaCoreService, MagmaCoreService> func) {
+    public void runInReadTransaction(final Function<MagmaCoreService, MagmaCoreService> func) {
         try {
-            database.begin();
+            database.beginRead();
+            func.apply(this);
+            database.commit();
+        } catch (final Exception e) {
+            database.abort();
+            throw e;
+        }
+    }
+
+    /**
+     * Run a {@link Function} in a transaction.
+     *
+     * @param func {@link Function} to run.
+     */
+    public void runInWriteTransaction(final Function<MagmaCoreService, MagmaCoreService> func) {
+        try {
+            database.beginWrite();
             func.apply(this);
             database.commit();
         } catch (final Exception e) {
@@ -743,7 +759,7 @@ public void runInTransaction(final Function<MagmaCoreService, MagmaCoreService>
      */
     public Map<String, Thing> findByEntityNameInTransaction(final List<String> entityNames) {
         try {
-            database.begin();
+            database.beginRead();
             final HashMap<String, Thing> result = new HashMap<String, Thing>();
 
             for (final String name : entityNames) {

core/src/main/java/uk/gov/gchq/magmacore/service/verify/DataIntegrityReport.java

@@ -586,7 +586,7 @@ public class DataIntegrityReport {
      * @return A {@link List} of {@link Thing} that represent data integrity errors.
      */
     public static List<Thing> verify(final MagmaCoreDatabase db) {
-        db.begin();
+        db.beginRead();
 
         final List<Thing> errors = new ArrayList<>();
 

core/src/test/java/uk/gov/gchq/magmacore/service/AssociationPatternTestData.java

@@ -331,7 +331,7 @@ static void createAssociationPattern(final MagmaCoreDatabase db) {
         community.addValue(HQDM.PARTICIPANT_IN, repBySign2Iri);
 
         // Persist all objects
-        db.begin();
+        db.beginWrite();
 
         db.create(userAssociationKind);
         db.create(managerKind);

core/src/test/java/uk/gov/gchq/magmacore/service/MagmaCoreServiceCreateDbTransformationTest.java

@@ -41,7 +41,7 @@ public void testCreateSuccess() {
 
         // Convert the new Thing to a DbTransformation and use it to persist the Thing.
         final DbTransformation transformation = svc.createDbTransformation(List.of(newThing));
-        svc.runInTransaction(transformation);
+        svc.runInWriteTransaction(transformation);
 
         // Retrieve the Thing and make sure it matches the original.
         final Map<String, Thing> foundThings = svc.findByEntityNameInTransaction(List.of(TEST_ENTITY_NAME));

core/src/test/java/uk/gov/gchq/magmacore/service/MagmaCoreServiceFindByKindOfAssociationTest.java

@@ -39,7 +39,7 @@ public void testFindSuccess() {
         now.addValue(HQDM.ENTITY_NAME, Instant.now().toString());
 
         // Find the required Things by sign in a transaction.
-        db.begin();
+        db.beginRead();
         final List<? extends Thing> participants = service
                 .findByKindOfAssociation(AssociationPatternTestData.userAssociationKindIri, now);
 

core/src/test/java/uk/gov/gchq/magmacore/service/MagmaCoreServiceFindByTypeKindAndSignPatternTest.java

@@ -37,7 +37,7 @@ public void testFindSuccess() {
         now.addValue(HQDM.ENTITY_NAME, Instant.now().toString());
 
         // Find the required Things by sign in a transaction.
-        db.begin();
+        db.beginRead();
         final List<? extends Thing> things = service.findByTypeKindAndSignPattern(
                 HQDM.PERSON,
                 SignPatternTestData.kindOfPersonIri,

core/src/test/java/uk/gov/gchq/magmacore/service/MagmaCoreServiceFindParticipantDetailsTest.java

@@ -60,7 +60,7 @@ public void testFindParticipantDetailsSuccess() throws MagmaCoreException {
         now.addValue(HQDM.ENTITY_NAME, Instant.now().toString());
 
         // Find the required Things by sign in a transaction.
-        db.begin();
+        db.beginRead();
         final Set<ParticipantDetails> found1 = service.findParticipantDetails(
                 AssociationPatternTestData.person1,
                 AssociationPatternTestData.system1,

core/src/test/java/uk/gov/gchq/magmacore/service/MagmaCoreServiceTest.java

@@ -55,17 +55,17 @@ public void test() {
 
         individual.addValue(HQDM.MEMBER_OF, "classOfIndividual");
 
-        database.begin();
+        database.beginWrite();
         database.create(individual);
         database.commit();
 
         individual.removeValue(HQDM.MEMBER_OF, "classOfIndividual");
 
-        database.begin();
+        database.beginWrite();
         database.update(individual);
         database.commit();
 
-        database.begin();
+        database.beginRead();
         final Thing individualFromDb = database.get(individualIri);
         database.commit();
 
@@ -95,7 +95,7 @@ public void testFindBySignSuccess() throws MagmaCoreException {
         now.addValue(HQDM.ENTITY_NAME, Instant.now().toString());
 
         // Find the required Things by sign in a transaction.
-        db.begin();
+        db.beginRead();
         final List<? extends Thing> found1 = service.findBySignValue(SignPatternTestData.community1,
                 SignPatternTestData.pattern1, "person1", now);
         final List<? extends Thing> found2 = service.findBySignValue(SignPatternTestData.community2,
@@ -143,7 +143,7 @@ public void testFindBySignWithNullSignValue() throws MagmaCoreException {
         now.addValue(HQDM.ENTITY_NAME, Instant.now().toString());
 
         // Find the required Things by sign in a transaction.
-        db.begin();
+        db.beginRead();
         final List<? extends Thing> found = service.findBySignValue(SignPatternTestData.community1,
                 SignPatternTestData.pattern1, null, now);
         db.commit();
@@ -170,7 +170,7 @@ public void testFindBySignWithBadPointInTime() throws MagmaCoreException {
         final PointInTime now = SpatioTemporalExtentServices.createPointInTime("now");
 
         // Find the required Things by sign in a transaction.
-        db.begin();
+        db.beginRead();
         final List<? extends Thing> found = service.findBySignValue(SignPatternTestData.community1,
                 SignPatternTestData.pattern1, "person1", now);
         db.commit();
@@ -197,14 +197,14 @@ public void testFindByPredicateOnly() {
         individual2.addValue(RDFS.RDF_TYPE, HQDM.INDIVIDUAL);
 
         // Create two objects.
-        svc.runInTransaction(mc -> {
+        svc.runInWriteTransaction(mc -> {
             mc.create(individual1);
             mc.create(individual2);
             return mc;
         });
 
         // Find individual2 since it's the only one with MEMBER_OF_KIND
-        svc.runInTransaction(mc -> {
+        svc.runInReadTransaction(mc -> {
             final List<Thing> result = mc.findByPredicateIriOnly(HQDM.MEMBER_OF_KIND);
 
             assertEquals(1, result.size());
@@ -213,7 +213,7 @@ public void testFindByPredicateOnly() {
         });
 
         // Find both individuals by RDF_TYPE IRI object.
-        svc.runInTransaction(mc -> {
+        svc.runInReadTransaction(mc -> {
             final List<Thing> result = mc.findByPredicateIriAndValue(RDFS.RDF_TYPE, HQDM.INDIVIDUAL);
 
             assertEquals(2, result.size());
@@ -224,7 +224,7 @@ public void testFindByPredicateOnly() {
         });
 
         // Find individual1 by a String value
-        svc.runInTransaction(mc -> {
+        svc.runInReadTransaction(mc -> {
             final List<Thing> result = mc.findByPredicateIriAndValue(HQDM.MEMBER_OF, "classOfIndividual");
 
             assertEquals(1, result.size());
@@ -252,7 +252,7 @@ public void testFindByPartialSignAndClassCaseInsensitive() throws MagmaCoreExcep
         now.addValue(HQDM.ENTITY_NAME, Instant.now().toString());
 
         // Find the required Things by sign in a transaction.
-        db.begin();
+        db.beginRead();
         final List<? extends Thing> found1 = service.findByPartialSignAndClass(
                 "person1", SignPatternTestData.classOfPersonIri, now);
         final List<? extends Thing> found2 = service.findByPartialSignAndClass(
@@ -290,7 +290,7 @@ public void testFindByPartialSignAndClassCaseSensitive() throws MagmaCoreExcepti
         now.addValue(HQDM.ENTITY_NAME, Instant.now().toString());
 
         // Find the required Things by sign in a transaction.
-        db.begin();
+        db.beginRead();
         final List<? extends Thing> found1 = service.findByPartialSignAndClassCaseSensitive(
                 "Person1", SignPatternTestData.classOfPersonIri, now);
         final List<? extends Thing> found2 = service.findByPartialSignAndClassCaseSensitive(

core/src/test/java/uk/gov/gchq/magmacore/service/SignPatternTestData.java

@@ -185,7 +185,7 @@ static void createSignPattern(final MagmaCoreDatabase db) {
         stateOfSign2.addValue(HQDM.PARTICIPANT_IN, new IRI(repBySign2.getId()));
 
         // Persist all objects
-        db.begin();
+        db.beginWrite();
 
         db.create(community1);
         db.create(community2);

core/src/test/java/uk/gov/gchq/magmacore/service/transformation/DbChangeSetTest.java

@@ -55,7 +55,7 @@ public void testApplyAndInvert() {
                         new DbCreateOperation(individualIri, HQDM.PART_OF_POSSIBLE_WORLD, possibleWorldIri)));
 
         // Apply the operations to the dataset.
-        mcService.runInTransaction(createIndividual);
+        mcService.runInWriteTransaction(createIndividual);
 
         // Find the individual and assert values are present.
         final Thing individual = mcService.getInTransaction(individualIri);
@@ -66,7 +66,7 @@ public void testApplyAndInvert() {
         assertTrue(individual.hasThisValue(HQDM.PART_OF_POSSIBLE_WORLD, possibleWorldIri));
 
         // Invert the operations and apply them in reverse order.
-        mcService.runInTransaction(DbChangeSet.invert(createIndividual));
+        mcService.runInWriteTransaction(DbChangeSet.invert(createIndividual));
 
         assertNull(mcService.getInTransaction(individualIri));
     }