diff --git a/data-store/src/main/java/org/lucares/pdb/datastore/internal/DataStore.java b/data-store/src/main/java/org/lucares/pdb/datastore/internal/DataStore.java
index 9e21d06..e2dcb83 100644
--- a/data-store/src/main/java/org/lucares/pdb/datastore/internal/DataStore.java
+++ b/data-store/src/main/java/org/lucares/pdb/datastore/internal/DataStore.java
@@ -267,7 +267,8 @@ public class DataStore implements AutoCloseable {
         final Tag keyPrefix = Tags.STRING_COMPRESSOR.createTag("", ""); // will find everything
 
         final PartitionIdSource partitionIdSource = new DatePartitioner(dateRange);
-        tagToDocsId.visitValues(partitionIdSource, keyPrefix, (tags, __) -> keys.add(tags.getKeyAsString()));
+        tagToDocsId.visitValues(partitionIdSource, keyPrefix,
+                (tag, __) -> keys.add(Tags.STRING_COMPRESSOR.getKeyAsString(tag)));
 
         keys.remove(ALL_DOCS_KEY);
         final List<String> result = new ArrayList<>(keys);
diff --git a/data-store/src/main/java/org/lucares/pdb/datastore/internal/QueryCompletionIndex.java b/data-store/src/main/java/org/lucares/pdb/datastore/internal/QueryCompletionIndex.java
index 56893a4..a198d6c 100644
--- a/data-store/src/main/java/org/lucares/pdb/datastore/internal/QueryCompletionIndex.java
+++ b/data-store/src/main/java/org/lucares/pdb/datastore/internal/QueryCompletionIndex.java
@@ -327,7 +327,7 @@ public class QueryCompletionIndex implements AutoCloseable {
         // create indices of all tags and all fields
         for (final Tag tag : listOfTagsA) {
             fieldToValueIndex.putValue(partitionId, tag, Empty.INSTANCE);
-            fieldIndex.putValue(partitionId, tag.getKeyAsString(), Empty.INSTANCE);
+            fieldIndex.putValue(partitionId, Tags.STRING_COMPRESSOR.getKeyAsString(tag), Empty.INSTANCE);
         }
     }
 
@@ -356,10 +356,10 @@ public class QueryCompletionIndex implements AutoCloseable {
         final PartitionIdSource partitionIdSource = new DatePartitioner(dateRange);
         tagToTagIndex.visitValues(partitionIdSource, keyPrefix, (k, v) -> {
 
-            final String vA = k.getTagA().getValueAsString();
+            final String vA = Tags.STRING_COMPRESSOR.getValueAsString(k.getTagA());
 
             if (valueA.matches(vA)) {
-                result.add(k.getTagB().getValueAsString());
+                result.add(Tags.STRING_COMPRESSOR.getValueAsString(k.getTagB()));
             }
         });
 
@@ -385,7 +385,7 @@ public class QueryCompletionIndex implements AutoCloseable {
 
         final PartitionIdSource partitionIdSource = new DatePartitioner(dateRange);
         tagToTagIndex.visitValues(partitionIdSource, keyPrefix, (k, v) -> {
-            result.add(k.getTagB().getValueAsString());
+            result.add(Tags.STRING_COMPRESSOR.getValueAsString(k.getTagB()));
         });
 
         return result;
@@ -406,7 +406,7 @@ public class QueryCompletionIndex implements AutoCloseable {
 
         final PartitionIdSource partitionIdSource = new DatePartitioner(dateRange);
         fieldToValueIndex.visitValues(partitionIdSource, keyPrefix, (k, v) -> {
-            result.add(k.getValueAsString());
+            result.add(Tags.STRING_COMPRESSOR.getValueAsString(k));
         });
 
         return result;
@@ -426,7 +426,7 @@ public class QueryCompletionIndex implements AutoCloseable {
             final String field) {
         final SortedSet<String> result = new TreeSet<>();
 
-        final TwoTags keyPrefix = new TwoTags(field, tag.getKeyAsString(), null, null);
+        final TwoTags keyPrefix = new TwoTags(field, Tags.STRING_COMPRESSOR.getKeyAsString(tag), null, null);
 
         final int negatedValueA = tag.getValue();
         final PartitionIdSource partitionIdSource = new DatePartitioner(dateRange);
@@ -434,7 +434,7 @@ public class QueryCompletionIndex implements AutoCloseable {
 
             final int valueA = k.getTagA().getValue();
             if (valueA != negatedValueA) {
-                result.add(k.getTagB().getValueAsString());
+                result.add(Tags.STRING_COMPRESSOR.getValueAsString(k.getTagB()));
             }
         });
 
diff --git a/data-store/src/main/java/org/lucares/pdb/datastore/internal/TagEncoderDecoder.java b/data-store/src/main/java/org/lucares/pdb/datastore/internal/TagEncoderDecoder.java
index 0b2c48e..8f7bd49 100644
--- a/data-store/src/main/java/org/lucares/pdb/datastore/internal/TagEncoderDecoder.java
+++ b/data-store/src/main/java/org/lucares/pdb/datastore/internal/TagEncoderDecoder.java
@@ -12,13 +12,13 @@ class TagEncoderDecoder implements EncoderDecoder<Tag> {
 
         final LongList keyAndValueCompressed = new LongList(2);
 
-        final String key = tag.getKeyAsString();
+        final String key = Tags.STRING_COMPRESSOR.getKeyAsString(tag);
         final byte[] result;
         if (!key.isEmpty()) {
             final Integer keyAsLong = Tags.STRING_COMPRESSOR.put(key);
             keyAndValueCompressed.add(keyAsLong);
 
-            final String value = tag.getValueAsString();
+            final String value = Tags.STRING_COMPRESSOR.getValueAsString(tag);
             if (!value.isEmpty()) {
                 final Integer valueAsLong = Tags.STRING_COMPRESSOR.put(value);
                 keyAndValueCompressed.add(valueAsLong);
diff --git a/data-store/src/main/java/org/lucares/pdb/datastore/lang/ExpressionToDocIdVisitor.java b/data-store/src/main/java/org/lucares/pdb/datastore/lang/ExpressionToDocIdVisitor.java
index 540d180..12103e0 100644
--- a/data-store/src/main/java/org/lucares/pdb/datastore/lang/ExpressionToDocIdVisitor.java
+++ b/data-store/src/main/java/org/lucares/pdb/datastore/lang/ExpressionToDocIdVisitor.java
@@ -150,8 +150,8 @@ public class ExpressionToDocIdVisitor extends ExpressionVisitor<PartitionLongLis
         for (final ParititionId partitionId : availablePartitionIds) {
             final List<LongList> docIdsForPartition = new ArrayList<>();
             keyToValueToDocId.visitValues(partitionId, Tags.STRING_COMPRESSOR.createTag(propertyName, ""),
-                    (tags, blockOffsetToDocIds) -> {
-                        if (valuePattern.matcher(tags.getValueAsString()).matches()) {
+                    (tag, blockOffsetToDocIds) -> {
+                        if (valuePattern.matcher(Tags.STRING_COMPRESSOR.getValueAsString(tag)).matches()) {
                             try (final LongStreamFile bsFile = diskStorage.streamExistingFile(blockOffsetToDocIds,
                                     partitionId)) {
 
diff --git a/pdb-api/src/main/java/org/lucares/pdb/api/StringCompressor.java b/pdb-api/src/main/java/org/lucares/pdb/api/StringCompressor.java
index 4317d36..48f84ca 100644
--- a/pdb-api/src/main/java/org/lucares/pdb/api/StringCompressor.java
+++ b/pdb-api/src/main/java/org/lucares/pdb/api/StringCompressor.java
@@ -51,4 +51,12 @@ public class StringCompressor {
         return new Tag(f, v);
     }
 
+    public String getKeyAsString(final Tag tag) {
+        return get(tag.getKey());
+    }
+
+    public String getValueAsString(final Tag tag) {
+        return get(tag.getValue());
+    }
+
 }
diff --git a/pdb-api/src/main/java/org/lucares/pdb/api/Tag.java b/pdb-api/src/main/java/org/lucares/pdb/api/Tag.java
index c75fc8d..51f652c 100644
--- a/pdb-api/src/main/java/org/lucares/pdb/api/Tag.java
+++ b/pdb-api/src/main/java/org/lucares/pdb/api/Tag.java
@@ -38,21 +38,13 @@ public class Tag implements Comparable<Tag> {
         return field;
     }
 
-    public String getKeyAsString() {
-        return Tags.STRING_COMPRESSOR.get(field);
-    }
-
     public int getValue() {
         return value;
     }
 
-    public String getValueAsString() {
-        return Tags.STRING_COMPRESSOR.get(value);
-    }
-
     @Override
     public String toString() {
-        return Tags.STRING_COMPRESSOR.get(field) + "=" + Tags.STRING_COMPRESSOR.get(value);
+        return field + "=" + value;
     }
 
     @Override
diff --git a/pdb-api/src/main/java/org/lucares/pdb/api/Tags.java b/pdb-api/src/main/java/org/lucares/pdb/api/Tags.java
index a91bb04..c693785 100644
--- a/pdb-api/src/main/java/org/lucares/pdb/api/Tags.java
+++ b/pdb-api/src/main/java/org/lucares/pdb/api/Tags.java
@@ -207,15 +207,6 @@ public class Tags implements Comparable<Tags> {
         return String.valueOf(tags);
     }
 
-    public String toCsv() {
-        final List<String> tagsAsStrings = new ArrayList<>();
-        for (final Tag tag : tags) {
-            tagsAsStrings.add(tag.getKeyAsString() + "=" + tag.getValueAsString());
-        }
-
-        return String.join(",", tagsAsStrings);
-    }
-
     @Override
     public int hashCode() {
         if (hashCode == 0) {