When using large transactions or a small log size, the database could get very slow.

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

@@ -334,10 +334,16 @@ public class PageStore implements CacheWriter {
         }
         synchronized (database) {
             database.checkPowerOff();
+            int firstUncommittedSection = getFirstUncommittedSection();
+            if (firstUncommittedSection <= log.getLogSectionId()) {
+                // can not truncate currently - avoid switching
+                return;
+            }
             writeIndexRowCounts();
             writeBack();
             log.checkpoint();
-            switchLog();
+            firstUncommittedSection = getFirstUncommittedSection();
+            log.removeUntil(firstUncommittedSection);
             // write back the free list
             writeBack();
             byte[] empty = new byte[pageSize];
@@ -548,8 +554,8 @@ public class PageStore implements CacheWriter {
         return p;
     }
 
-    private void switchLog() {
-        trace.debug("switchLog");
+    private int getFirstUncommittedSection() {
+        trace.debug("getFirstUncommittedSection");
         Session[] sessions = database.getSessions(true);
         int firstUncommittedSection = log.getLogSectionId();
         for (int i = 0; i < sessions.length; i++) {
@@ -561,7 +567,7 @@ public class PageStore implements CacheWriter {
                 }
             }
         }
-        log.removeUntil(firstUncommittedSection);
+        return firstUncommittedSection;
     }
 
     private void readStaticHeader() {
@@ -1049,7 +1055,8 @@ public class PageStore implements CacheWriter {
         if (!database.isReadOnly()) {
             if (log.getInDoubtTransactions().size() == 0) {
                 log.recoverEnd();
-                switchLog();
+                int firstUncommittedSection = getFirstUncommittedSection();
+                log.removeUntil(firstUncommittedSection);
             } else {
                 setReadOnly = true;
             }

h2/src/test/org/h2/test/unit/TestPageStore.java

@@ -35,6 +35,7 @@ public class TestPageStore extends TestBase implements DatabaseEventListener {
     }
 
     public void test() throws Exception {
+        testCheckpoint();
         testDropRecreate();
         testDropAll();
         testCloseTempTable();
@@ -58,6 +59,26 @@ public class TestPageStore extends TestBase implements DatabaseEventListener {
         testFuzzOperations();
     }
 
+    private void testCheckpoint() throws SQLException {
+        deleteDb("pageStore");
+        Connection conn;
+        conn = getConnection("pageStore");
+        Statement stat = conn.createStatement();
+        stat.execute("create table test(data varchar)");
+        stat.execute("create sequence seq");
+        stat.execute("set max_log_size 1");
+        conn.setAutoCommit(false);
+        stat.execute("insert into test select space(1000) from system_range(1, 1000)");
+        long before = System.currentTimeMillis();
+        stat.execute("select nextval('SEQ') from system_range(1, 100000)");
+        long after = System.currentTimeMillis();
+        // it's hard to test - basically it shouldn't to too many checkpoint operations
+        assertTrue(after - before < 10000);
+        stat.execute("drop table test");
+        stat.execute("drop sequence seq");
+        conn.close();
+    }
+
     private void testDropRecreate() throws SQLException {
         if (config.memory) {
             return;