fix

Author: JingsongLi

paimon-common/src/main/java/org/apache/paimon/lookup/sort/db/SimpleLsmKvDb.java

@@ -72,6 +72,21 @@ public class SimpleLsmKvDb implements Closeable {
     /** Maximum number of levels in the LSM tree. */
     static final int MAX_LEVELS = 4;
 
+    /**
+     * Estimated per-entry memory overhead in the MemTable's TreeMap, beyond the raw key/value
+     * bytes. This accounts for:
+     *
+     * <ul>
+     *   <li>TreeMap.Entry node: ~64 bytes (object header + left/right/parent/key/value refs +
+     *       color)
+     *   <li>MemorySlice wrapper: ~32 bytes (object header + segment ref + offset + length)
+     *   <li>MemorySegment backing the key: ~48 bytes (object header + heapMemory/offHeapBuffer refs
+     *       + address + size)
+     *   <li>byte[] value array header: ~16 bytes (object header + length)
+     * </ul>
+     */
+    static final long PER_ENTRY_OVERHEAD = 160;
+
     private final File dataDirectory;
     private final SortLookupStoreFactory storeFactory;
     private final Comparator<MemorySlice> keyComparator;
@@ -180,6 +195,8 @@ public void put(byte[] key, byte[] value) throws IOException {
         long delta = key.length + value.length;
         if (oldValue != null) {
             delta -= (key.length + oldValue.length);
+        } else {
+            delta += PER_ENTRY_OVERHEAD;
         }
         memTableSize += delta;
         maybeFlushMemTable();
@@ -197,6 +214,8 @@ public void delete(byte[] key) throws IOException {
         long delta = key.length;
         if (oldValue != null) {
             delta -= (key.length + oldValue.length);
+        } else {
+            delta += PER_ENTRY_OVERHEAD;
         }
         memTableSize += delta;
         maybeFlushMemTable();