do not use static string compressor in upload handlers

data-store/src/main/java/org/lucares/pdb/datastore/internal/DataStore.java

@@ -163,6 +163,10 @@ public class DataStore implements AutoCloseable {
         }
     }
 
+    public StringCompressor getStringCompressor() {
+        return stringCompressor;
+    }
+
     // visible for test
     QueryCompletionIndex getQueryCompletionIndex() {
         return queryCompletionIndex;