This is an automated email from the ASF dual-hosted git repository.
desruisseaux pushed a commit to branch geoapi-4.0
in repository https://gitbox.apache.org/repos/asf/sis.git
commit a17e58e5dec158c1862c42367cb13b7190e33706
Author: Martin Desruisseaux <martin.desruisse...@geomatys.com>
AuthorDate: Wed Aug 14 14:09:31 2024 +0200
Add read/write lock for databases that do not support concurrent
transactions.
This is the case of SQLite used for Geopackage.
---
.../apache/sis/storage/sql/feature/Database.java | 14 +++++++
.../sis/storage/sql/feature/FeatureStream.java | 4 ++
.../org/apache/sis/util/stream/DeferredStream.java | 49 +++++++++++++++++++---
3 files changed, 61 insertions(+), 6 deletions(-)
diff --git
a/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/storage/sql/feature/Database.java
b/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/storage/sql/feature/Database.java
index ed49071ea5..75c9a39306 100644
---
a/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/storage/sql/feature/Database.java
+++
b/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/storage/sql/feature/Database.java
@@ -28,6 +28,8 @@ import java.util.ArrayList;
import java.util.Locale;
import java.util.Optional;
import java.util.logging.LogRecord;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.sql.Array;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
@@ -202,6 +204,17 @@ public class Database<G> extends Syntax {
*/
private SelectionClauseWriter filterToSQL;
+ /**
+ * The lock for read or write operations in the SQL database, or {@code
null} if none.
+ * The read or write lock should be obtained before to get a connection
for executing
+ * a statement, and released after closing the connection. Locking is
assumed unneeded
+ * for obtaining database metadata.
+ *
+ * <p>This field should be null if the database manages concurrent
transactions by itself.
+ * It is non-null only as a workaround for databases that do not support
concurrency.</p>
+ */
+ protected final ReadWriteLock transactionLocks;
+
/**
* Where to send warnings.
*
@@ -280,6 +293,7 @@ public class Database<G> extends Syntax {
supportsSchemas = metadata.supportsSchemasInDataManipulation();
supportsJavaTime = dialect.supportsJavaTime();
crsEncodings = EnumSet.noneOf(CRSEncoding.class);
+ transactionLocks = dialect.supportsConcurrency() ? null : new
ReentrantReadWriteLock();
}
/**
diff --git
a/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/storage/sql/feature/FeatureStream.java
b/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/storage/sql/feature/FeatureStream.java
index 196c9887cd..4b9c31c00e 100644
---
a/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/storage/sql/feature/FeatureStream.java
+++
b/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/storage/sql/feature/FeatureStream.java
@@ -327,6 +327,7 @@ final class FeatureStream extends DeferredStream<Feature> {
if (selection != null && !selection.isEmpty()) {
sql.append(" WHERE ").append(selection.toString());
}
+ lock(table.database.transactionLocks);
try (Connection connection = getConnection()) {
makeReadOnly(connection);
try (Statement st = connection.createStatement();
@@ -339,6 +340,8 @@ final class FeatureStream extends DeferredStream<Feature> {
}
} catch (SQLException e) {
throw new BackingStoreException(e);
+ } finally {
+ unlock();
}
return Math.max(super.count() - offset, 0);
}
@@ -395,6 +398,7 @@ final class FeatureStream extends DeferredStream<Feature> {
final String filter = (selection != null && !selection.isEmpty()) ?
selection.toString() : null;
selection = null; // Let the garbage collector do its work.
+ lock(table.database.transactionLocks);
final Connection connection = getConnection();
setCloseHandler(connection); // Executed only if `FeatureIterator`
creation fails, discarded later otherwise.
makeReadOnly(connection);
diff --git
a/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/util/stream/DeferredStream.java
b/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/util/stream/DeferredStream.java
index 849dbba28a..56894d613b 100644
---
a/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/util/stream/DeferredStream.java
+++
b/endorsed/src/org.apache.sis.storage.sql/main/org/apache/sis/util/stream/DeferredStream.java
@@ -19,6 +19,8 @@ package org.apache.sis.util.stream;
import java.util.Spliterator;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReadWriteLock;
import org.apache.sis.util.Exceptions;
import org.apache.sis.util.collection.BackingStoreException;
@@ -66,19 +68,35 @@ public abstract class DeferredStream<T> extends
StreamWrapper<T> {
*/
AutoCloseable handler;
+ /**
+ * If there is a read or write lock to unlock, that lock. Otherwise
{@code null}.
+ * This is non-null only with databases that do not support concurrent
transactions well.
+ *
+ * @see #lock(ReadWriteLock)
+ */
+ Lock lock;
+
/**
* Invoked by the stream for disposing the resources.
*/
@Override
public void run() {
final AutoCloseable h = handler;
+ final Lock c = lock;
handler = null;
- if (h != null) try {
- h.close();
- } catch (RuntimeException e) {
- throw e;
- } catch (Exception e) {
- throw new BackingStoreException(e);
+ lock = null;
+ try {
+ if (h != null) try {
+ h.close();
+ } catch (RuntimeException e) {
+ throw e;
+ } catch (Exception e) {
+ throw new BackingStoreException(e);
+ }
+ } finally {
+ if (c != null) {
+ c.unlock();
+ }
}
}
}
@@ -161,4 +179,23 @@ public abstract class DeferredStream<T> extends
StreamWrapper<T> {
protected final void setCloseHandler(final AutoCloseable handler) {
closeHandler.handler = handler;
}
+
+ /**
+ * Sets the read lock.
+ * Locks are used only with databases that do not support concurrent
transactions well.
+ *
+ * @param lock the lock, or {@code null} if none.
+ */
+ protected final void lock(final ReadWriteLock lock) {
+ if (lock != null) {
+ (closeHandler.lock = lock.readLock()).lock();
+ }
+ }
+
+ /**
+ * Closes the connection (if any) and unlock.
+ */
+ protected final void unlock() {
+ closeHandler.run();
+ }
}
