Page store: new write and read counters in the meta data table.

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,11 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>The SQL syntax is documented using (railroad) diagrams.
+<ul><li>Page store: new write and read counters in the meta data table. Use 
+    SELECT * FROM INFORMATION_SCHEMA.SETTINGS WHERE NAME IN(
+    'info.FILE_WRITE_TOTAL', 'info.FILE_WRITE', 'info.FILE_READ', 
+    'info.CACHE_MAX_SIZE', 'info.CACHE_SIZE')
+</li><li>The SQL syntax is documented using (railroad) diagrams.
     The diagrams are HTML.
 </li><li>The documentation is no longer available in Japanese because the
     translation was too much out of sync. Please use the Google translation instead.

h2/src/docsrc/html/roadmap.html

@@ -205,6 +205,10 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
 </li><li>Updatable result set on table without primary key or unique index
 </li><li>Use LinkedList instead of ArrayList where applicable
 </li><li>Support % operator (modulo)
+</li><li>Support JMX: create an MBean for each database and server (support JConsole).
+    See http://thedevcloud.blogspot.com/2008/10/displaying-hsql-database-manager-in.html
+    http://java.sun.com/j2se/1.5.0/docs/api/java/lang/management/ManagementFactory.html#getPlatformMBeanServer()
+    http://java.sun.com/j2se/1.5.0/docs/guide/management/agent.html
 </li><li>Support 1+'2'=3, '1'+'2'='12' (MS SQL Server compatibility)
 </li><li>Support nested transactions
 </li><li>Add a benchmark for big databases, and one for many users
@@ -241,10 +245,6 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
 </li><li>Ability to resize the cache array when resizing the cache
 </li><li>Time based cache writing (one second after writing the log)
 </li><li>Check state of H2 driver for DDLUtils: https://issues.apache.org/jira/browse/DDLUTILS-185
-</li><li>Support JMX: create an MBean for each database and server (support JConsole).
-    See http://thedevcloud.blogspot.com/2008/10/displaying-hsql-database-manager-in.html
-    http://java.sun.com/j2se/1.5.0/docs/api/java/lang/management/ManagementFactory.html#getPlatformMBeanServer()
-    http://java.sun.com/j2se/1.5.0/docs/guide/management/agent.html
 </li><li>Index usage for REGEXP LIKE.
 </li><li>Compatibility: add a role DBA (like ADMIN).
 </li><li>Better support multiple processors for in-memory databases.

h2/src/main/org/h2/log/LogSystem.java

@@ -716,7 +716,7 @@ public class LogSystem {
      */
     public String getWritePos() {
         if (pageStore != null) {
-            return "" + pageStore.getWriteCount();
+            return "" + pageStore.getWriteCountTotal();
         }
         return currentLog.getId() + "/" + currentLog.getPos();
     }

h2/src/main/org/h2/store/PageStore.java

@@ -72,7 +72,7 @@ import org.h2.value.ValueString;
  * The format of page 1 and 2 is:
  * <ul>
  * <li>CRC32 of the remaining data: int (0-3)</li>
- * <li>write counter (incremented each time the header changes): long (4-11)</li>
+ * <li>write counter (incremented each time something is written): long (4-11)</li>
  * <li>log trunk key: int (12-15)</li>
  * <li>log trunk page (0 for none): int (16-19)</li>
  * <li>log data page (0 for none): int (20-23)</li>
@@ -163,7 +163,7 @@ public class PageStore implements CacheWriter {
     private String accessMode;
     private int pageSize;
     private int pageSizeShift;
-    private long writeCount;
+    private long writeCountBase, writeCount, readCount;
     private int logKey, logFirstTrunkPage, logFirstDataPage;
 
     private Cache cache;
@@ -240,6 +240,7 @@ public class PageStore implements CacheWriter {
                 }
                 file.seek((long) pageId << pageSizeShift);
                 file.readFullyDirect(buffer, 0, pageSize);
+                readCount++;
                 out.write(buffer, 0, pageSize);
                 return pageId + 1;
             } catch (IOException e) {
@@ -411,7 +412,11 @@ public class PageStore implements CacheWriter {
         // the easiest way to remove superfluous entries
         freeLists.clear();
         trace.debug("pageCount:" + pageCount);
-        file.setLength((long) pageCount << pageSizeShift);
+        long newLength = (long) pageCount << pageSizeShift;
+        if (file.length() != newLength) {
+            file.setLength(newLength);
+            writeCount++;
+        }
     }
 
     private void compact(int full) throws SQLException {
@@ -546,6 +551,7 @@ public class PageStore implements CacheWriter {
         file.seek(FileStore.HEADER_LENGTH);
         Data page = Data.create(database, new byte[PAGE_SIZE_MIN - FileStore.HEADER_LENGTH]);
         file.readFully(page.getBytes(), 0, PAGE_SIZE_MIN - FileStore.HEADER_LENGTH);
+        readCount++;
         setPageSize(page.readInt());
         int writeVersion = page.readByte();
         int readVersion = page.readByte();
@@ -573,7 +579,7 @@ public class PageStore implements CacheWriter {
             int expected = (int) crc.getValue();
             int got = page.readInt();
             if (expected == got) {
-                writeCount = page.readLong();
+                writeCountBase = page.readLong();
                 logKey = page.readInt();
                 logFirstTrunkPage = page.readInt();
                 logFirstDataPage = page.readInt();
@@ -616,6 +622,7 @@ public class PageStore implements CacheWriter {
         page.writeByte((byte) READ_VERSION);
         file.seek(FileStore.HEADER_LENGTH);
         file.write(page.getBytes(), 0, pageSize - FileStore.HEADER_LENGTH);
+        writeCount++;
     }
 
     /**
@@ -649,7 +656,7 @@ public class PageStore implements CacheWriter {
         file.write(page.getBytes(), 0, pageSize);
         file.seek(pageSize + pageSize);
         file.write(page.getBytes(), 0, pageSize);
-        writeCount++;
+        // don't increment the write counter, because it was just written
     }
 
     /**
@@ -927,6 +934,7 @@ public class PageStore implements CacheWriter {
             }
             file.seek((long) pos << pageSizeShift);
             file.readFully(page.getBytes(), 0, pageSize);
+            readCount++;
         }
     }
 
@@ -1430,7 +1438,16 @@ public class PageStore implements CacheWriter {
     }
 
     /**
-     * Get the write count.
+     * Get the file write count since the database was created.
+     *
+     * @return the write count
+     */
+    public long getWriteCountTotal() {
+        return writeCount + writeCountBase;
+    }
+
+    /**
+     * Get the file write count since the database was opened.
      *
      * @return the write count
      */
@@ -1438,6 +1455,15 @@ public class PageStore implements CacheWriter {
         return writeCount;
     }
 
+    /**
+     * Get the file read count since the database was opened.
+     *
+     * @return the read count
+     */
+    public long getReadCount() {
+        return readCount;
+    }
+
     /**
      * A table is truncated.
      *

h2/src/main/org/h2/table/MetaTable.java

@@ -49,6 +49,7 @@ import org.h2.schema.SchemaObject;
 import org.h2.schema.Sequence;
 import org.h2.schema.TriggerObject;
 import org.h2.store.DiskFile;
+import org.h2.store.PageStore;
 import org.h2.tools.Csv;
 import org.h2.util.MathUtils;
 import org.h2.util.ObjectArray;
@@ -868,6 +869,14 @@ public class MetaTable extends Table {
             add(rows, "h2.serverCachedObjects", "" + SysProperties.SERVER_CACHED_OBJECTS);
             add(rows, "h2.serverResultSetFetchSize", "" + SysProperties.SERVER_RESULT_SET_FETCH_SIZE);
             add(rows, "h2.sortNullsHigh", "" + SysProperties.SORT_NULLS_HIGH);
+            if (database.isPageStoreEnabled() && database.isPersistent()) {
+                PageStore store = database.getPageStore();
+                add(rows, "info.FILE_WRITE_TOTAL", "" + store.getWriteCountTotal());
+                add(rows, "info.FILE_WRITE", "" + store.getWriteCount());
+                add(rows, "info.FILE_READ", "" + store.getReadCount());
+                add(rows, "info.CACHE_MAX_SIZE", "" + store.getCache().getMaxSize());
+                add(rows, "info.CACHE_SIZE", "" + store.getCache().getSize());
+            }
             DiskFile dataFile = database.getDataFile();
             if (dataFile != null) {
                 add(rows, "CACHE_TYPE", dataFile.getCache().getTypeName());