Split file system: truncating a file now deletes the parts in reverse order, so…

Split file system: truncating a file now deletes the parts in reverse order, so that the file list is consistent if the process is interrupted while truncating.

h2/src/docsrc/html/changelog.html

@@ -17,7 +17,9 @@ Change Log
 
 <h1>Change Log</h1>
 <h2>Next Version (unreleased)</h2>
-<ul><li>The H2 JDBC client can now be used in an unsigned Applet.
+<ul><li>Split file system: truncating a file now deletes the parts in reverse order,
+    so that the file list is consistent if the process is interrupted while truncating.
+</li><li>The H2 JDBC client can now be used in an unsigned Applet.
     The problem was that System.getProperty throws a SecurityException, which is now ignored.
 </li><li>The condition "in(select ...)" did not work correctly if the subquery
     could not be converted to a "distinct" query, as in:

h2/src/main/org/h2/store/fs/FileObjectSplit.java

@@ -96,25 +96,31 @@ public class FileObjectSplit implements FileObject {
             FileObject[] newList = new FileObject[newFileCount];
             int max = Math.max(newFileCount, list.length);
             long remaining = newLength;
+            // delete backwards, so that truncating is somewhat transactional
+            for (int i = list.length - 1; i >= newFileCount; i--) {
+                // verify the file is writable
+                list[i].setFileLength(0);
+                list[i].close();
+                try {
+                    IOUtils.delete(list[i].getName());
+                } catch (DbException e) {
+                    throw DbException.convertToIOException(e);
+                }
+            }
             for (int i = 0; i < max; i++) {
-                long size = Math.min(remaining, maxLength);
-                remaining -= size;
+                long fileSize = Math.min(remaining, maxLength);
+                remaining -= fileSize;
                 if (i >= newFileCount) {
-                    list[i].close();
-                    try {
-                        IOUtils.delete(list[i].getName());
-                    } catch (DbException e) {
-                        throw DbException.convertToIOException(e);
-                    }
+                    // already closed and deleted
                 } else if (i >= list.length) {
                     String fileName = FileSystemSplit.getFileName(name, i);
                     FileObject o = FileSystem.getInstance(fileName).openFileObject(fileName, mode);
-                    o.setFileLength(size);
+                    o.setFileLength(fileSize);
                     newList[i] = o;
                 } else {
                     FileObject o = list[i];
-                    if (o.length() != size) {
-                        o.setFileLength(size);
+                    if (o.length() != fileSize) {
+                        o.setFileLength(fileSize);
                     }
                     newList[i] = list[i];
                 }