serialized some database access methods

source/net/yacy/kelondro/table/SplitTable.java

@@ -320,8 +320,10 @@ public class SplitTable implements Index, Iterable<Row.Entry> {
     public Row.Entry get(final byte[] key, final boolean forcecopy) throws IOException {
         final Index keeper = keeperOf(key);
         if (keeper == null) return null;
+        synchronized (this) { // avoid concurrent IO from different methods
             return keeper.get(key, forcecopy);
         }
+    }
 
     @Override
     public Map<byte[], Row.Entry> get(final Collection<byte[]> keys, final boolean forcecopy) throws IOException, InterruptedException {
@@ -376,8 +378,10 @@ public class SplitTable implements Index, Iterable<Row.Entry> {
     public Row.Entry replace(final Row.Entry row) throws IOException, RowSpaceExceededException {
         assert row.objectsize() <= this.rowdef.objectsize;
         Index keeper = keeperOf(row.getPrimaryKeyBytes());
-        if (keeper != null) return keeper.replace(row);
+        if (keeper != null) synchronized (this) { // avoid concurrent IO from different methods
-        synchronized (this.tables) {
+            return keeper.replace(row);
+        }
+        synchronized (this) {
             assert this.current == null || this.tables.get(this.current) != null : "this.current = " + this.current;
             keeper = (this.current == null) ? newTable() : checkTable(this.tables.get(this.current));
         }
@@ -397,12 +401,11 @@ public class SplitTable implements Index, Iterable<Row.Entry> {
         assert row.objectsize() <= this.rowdef.objectsize;
         final byte[] key = row.getPrimaryKeyBytes();
         if (this.tables == null) return true;
-        Index keeper = null;
+        Index keeper = keeperOf(key);
-        synchronized (this.tables) {
+        if (keeper != null) synchronized (this) { // avoid concurrent IO from different methods
-            keeper = keeperOf(key);
+            return keeper.put(row);
         }
-        if (keeper != null) return keeper.put(row);
+        synchronized (this) {
-        synchronized (this.tables) {
             keeper = keeperOf(key); // we must check that again because it could have changed in between
             if (keeper != null) return keeper.put(row);
             assert this.current == null || this.tables.get(this.current) != null : "this.current = " + this.current;
@@ -425,12 +428,12 @@ public class SplitTable implements Index, Iterable<Row.Entry> {
     @Override
     public void addUnique(final Row.Entry row) throws IOException, RowSpaceExceededException {
         assert row.objectsize() <= this.rowdef.objectsize;
-        Index table = (this.current == null) ? null : this.tables.get(this.current);
+        Index keeper = (this.current == null) ? null : this.tables.get(this.current);
-        synchronized (this.tables) {
+        synchronized (this) {
             assert this.current == null || this.tables.get(this.current) != null : "this.current = " + this.current;
-            if (table == null) table = newTable(); else table = checkTable(table);
+            if (keeper == null) keeper = newTable(); else keeper = checkTable(keeper);
         }
-        table.addUnique(row);
+        keeper.addUnique(row);
     }
 
     @Override
@@ -447,15 +450,19 @@ public class SplitTable implements Index, Iterable<Row.Entry> {
     public boolean delete(final byte[] key) throws IOException {
         final Index table = keeperOf(key);
         if (table == null) return false;
+        synchronized (this) { // avoid concurrent IO from different methods
             return table.delete(key);
         }
+    }
 
     @Override
     public Row.Entry remove(final byte[] key) throws IOException {
         final Index table = keeperOf(key);
         if (table == null) return null;
+        synchronized (this) { // avoid concurrent IO from different methods
             return table.remove(key);
         }
+    }
 
     @Override
     public Row.Entry removeOne() throws IOException {
@@ -472,8 +479,10 @@ public class SplitTable implements Index, Iterable<Row.Entry> {
         if (maxtable == null) {
             return null;
         }
+        synchronized (this) { // avoid concurrent IO from different methods
             return maxtable.removeOne();
         }
+    }
 
     @Override
     public List<Row.Entry> top(final int count) throws IOException {
@@ -490,8 +499,10 @@ public class SplitTable implements Index, Iterable<Row.Entry> {
         if (maxtable == null) {
             return null;
         }
+        synchronized (this) { // avoid concurrent IO from different methods
             return maxtable.top(count);
         }
+    }
 
     @Override
     public CloneableIterator<byte[]> keys(final boolean up, final byte[] firstKey) throws IOException {

source/net/yacy/search/index/MetadataRepository.java

@@ -599,6 +599,7 @@ public final class MetadataRepository implements Iterable<byte[]> {
     public Map<String, URLHashCounter> domainSampleCollector() throws IOException {
         final Map<String, URLHashCounter> map = new HashMap<String, URLHashCounter>();
         // first collect all domains and calculate statistics about it
+        synchronized (this) {
             final CloneableIterator<byte[]> i = this.urlIndexFile.keys(true, null);
             String hosthash;
             byte[] urlhashb;
@@ -614,6 +615,7 @@ public final class MetadataRepository implements Iterable<byte[]> {
                     ds.count++;
                 }
             }
+        }
         return map;
     }
 
@@ -739,12 +741,14 @@ public final class MetadataRepository implements Iterable<byte[]> {
         // first collect all url hashes that belong to the domain
         assert hosthash.length() == 6;
         final ArrayList<String> l = new ArrayList<String>();
+        synchronized (this) {
             final CloneableIterator<byte[]> i = this.urlIndexFile.keys(true, null);
             String hash;
             while (i != null && i.hasNext()) {
                 hash = ASCII.String(i.next());
                 if (hosthash.equals(hash.substring(6))) l.add(hash);
             }
+        }
 
         // then delete the urls using this list
         int cnt = 0;