Examples with DefaultNodePropertyAccessor org.neo4j.kernel.impl.transaction.state.storeview.DefaultNodePropertyAccessor used on opensource projects

Example 1 with DefaultNodePropertyAccessor

use of org.neo4j.kernel.impl.transaction.state.storeview.DefaultNodePropertyAccessor in project neo4j by neo4j.

the class ConstraintIndexCreator method createUniquenessConstraintIndex.

/**
 * You MUST hold a label write lock before you call this method.
 * However the label write lock is temporarily released while populating the index backing the constraint.
 * It goes a little like this:
 * <ol>
 * <li>Prerequisite: Getting here means that there's an open schema transaction which has acquired the
 * LABEL WRITE lock.</li>
 * <li>Index schema rule which is backing the constraint is created in a nested mini-transaction
 * which doesn't acquire any locking, merely adds tx state and commits so that the index rule is applied
 * to the store, which triggers the index population</li>
 * <li>Release the LABEL WRITE lock</li>
 * <li>Await index population to complete</li>
 * <li>Acquire the LABEL WRITE lock (effectively blocking concurrent transactions changing
 * data related to this constraint, and it so happens, most other transactions as well) and verify
 * the uniqueness of the built index</li>
 * <li>Leave this method, knowing that the uniqueness constraint rule will be added to tx state
 * and this tx committed, which will create the uniqueness constraint</li>
 * </ol>
 */
public IndexDescriptor createUniquenessConstraintIndex(KernelTransactionImplementation transaction, IndexBackedConstraintDescriptor constraint, IndexPrototype prototype) throws TransactionFailureException, CreateConstraintFailureException, UniquePropertyValueValidationException, AlreadyConstrainedException {
    String constraintString = constraint.userDescription(transaction.tokenRead());
    log.info("Starting constraint creation: %s.", constraintString);
    IndexDescriptor index;
    SchemaRead schemaRead = transaction.schemaRead();
    try {
        index = checkAndCreateConstraintIndex(schemaRead, transaction.tokenRead(), constraint, prototype);
    } catch (AlreadyConstrainedException e) {
        throw e;
    } catch (KernelException e) {
        throw new CreateConstraintFailureException(constraint, e);
    }
    boolean success = false;
    boolean reacquiredLabelLock = false;
    Client locks = transaction.lockClient();
    ResourceType keyType = constraint.schema().keyType();
    long[] lockingKeys = constraint.schema().lockingKeys();
    try {
        locks.acquireShared(transaction.lockTracer(), keyType, lockingKeys);
        IndexProxy proxy = indexingService.getIndexProxy(index);
        // Release the LABEL WRITE lock during index population.
        // At this point the integrity of the constraint to be created was checked
        // while holding the lock and the index rule backing the soon-to-be-created constraint
        // has been created. Now it's just the population left, which can take a long time
        locks.releaseExclusive(keyType, lockingKeys);
        awaitConstraintIndexPopulation(constraint, proxy, transaction);
        log.info("Constraint %s populated, starting verification.", constraintString);
        // Index population was successful, but at this point we don't know if the uniqueness constraint holds.
        // Acquire LABEL WRITE lock and verify the constraints here in this user transaction
        // and if everything checks out then it will be held until after the constraint has been
        // created and activated.
        locks.acquireExclusive(transaction.lockTracer(), keyType, lockingKeys);
        reacquiredLabelLock = true;
        try (NodePropertyAccessor propertyAccessor = new DefaultNodePropertyAccessor(transaction.newStorageReader(), transaction.cursorContext(), transaction.memoryTracker())) {
            indexingService.getIndexProxy(index).verifyDeferredConstraints(propertyAccessor);
        }
        log.info("Constraint %s verified.", constraintString);
        success = true;
        return index;
    } catch (IndexNotFoundKernelException e) {
        String indexString = index.userDescription(transaction.tokenRead());
        throw new TransactionFailureException(format("Index (%s) that we just created does not exist.", indexString), e);
    } catch (IndexEntryConflictException e) {
        throw new UniquePropertyValueValidationException(constraint, VERIFICATION, e, transaction.tokenRead());
    } catch (InterruptedException | IOException e) {
        throw new CreateConstraintFailureException(constraint, e);
    } finally {
        if (!success) {
            if (!reacquiredLabelLock) {
                locks.acquireExclusive(transaction.lockTracer(), keyType, lockingKeys);
            }
            if (indexStillExists(schemaRead, index)) {
                dropUniquenessConstraintIndex(index);
            }
        }
    }
}