fix performance regression

The last improvement of memory usage introduced a performance
regression. The ingestion performance dropped by 50%-80%, because
for every inserted entry the Tags were created inefficient.

pdb-api/src/main/java/org/lucares/pdb/api/Entry.java

@@ -65,7 +65,7 @@ public class Entry {
 		}
 
 		final OffsetDateTime date = getDate();
-		return date.format(DateTimeFormatter.ISO_ZONED_DATE_TIME) + " = " + value + " (" + tags + ")";
+		return date.format(DateTimeFormatter.ISO_ZONED_DATE_TIME) + " = " + value + " (" + tags.asString() + ")";
 	}
 
 	@Override

pdb-api/src/main/java/org/lucares/pdb/api/TagByKeyComparator.java

@@ -0,0 +1,15 @@
+package org.lucares.pdb.api;
+
+import java.io.Serializable;
+import java.util.Comparator;
+
+public class TagByKeyComparator implements Comparator<Tag>, Serializable {
+
+	private static final long serialVersionUID = -6683582291996307323L;
+	public static final TagByKeyComparator INSTANCE = new TagByKeyComparator();
+
+	@Override
+	public int compare(final Tag a, final Tag b) {
+		return a.getKey().compareToIgnoreCase(b.getKey());
+	}
+}

pdb-api/src/main/java/org/lucares/pdb/api/Tags.java

@@ -1,5 +1,7 @@
 package org.lucares.pdb.api;
 
+import java.util.Arrays;
+import java.util.Collection;
 import java.util.List;
 import java.util.Objects;
 import java.util.Set;
@@ -47,49 +49,30 @@ public class Tags {
 		}
 	}
 
+	public static Tags create(final Collection<Tag> tags) {
+		final String newFilename = toFilename(tags);
+
+		return new Tags(newFilename);
+	}
+
 	public static Tags create() {
 		return EMPTY;
 	}
 
 	public static Tags create(final String key, final String value) {
 
-		return EMPTY.copyAdd(key, value);
+		return TagsBuilder.create().add(key, value).build();
 	}
 
 	public static Tags create(final String key1, final String value1, final String key2, final String value2) {
 
-		final Tags result = EMPTY.copyAdd(key1, value1).copyAdd(key2, value2);
+		final Tags result = TagsBuilder.create().add(key1, value1).add(key2, value2).build();
 		return result;
 	}
 
 	public static Tags create(final String key1, final String value1, final String key2, final String value2,
 			final String key3, final String value3) {
-		final Tags result = EMPTY.copyAdd(key1, value1).copyAdd(key2, value2).copyAdd(key3, value3);
-		return result;
-	}
-
-	public Tags copyAdd(final String key, final String value) {
-		Objects.requireNonNull(key, "key must not be null");
-		Objects.requireNonNull(value, "value must not be null");
-
-		final Tag tag = new Tag(key, value);
-
-		final SortedSet<Tag> tags = toTags();
-		tags.add(tag);
-
-		final String newFilename = toFilename(tags);
-
-		return new Tags(newFilename);
-	}
-
-	public Tags copyAddIfNotNull(final String key, final String value) {
-
-		final Tags result;
-		if (value != null) {
-			result = copyAdd(key, value);
-		} else {
-			result = this;
-		}
+		final Tags result = TagsBuilder.create().add(key1, value1).add(key2, value2).add(key3, value3).build();
 		return result;
 	}
 
@@ -109,7 +92,7 @@ public class Tags {
 	}
 
 	private SortedSet<Tag> toTags() {
-		final SortedSet<Tag> result = new TreeSet<>((a, b) -> a.getKey().compareToIgnoreCase(b.getKey()));
+		final SortedSet<Tag> result = new TreeSet<>(TagByKeyComparator.INSTANCE);
 		final Matcher matcher = EXTRACT_TAGS_PATTERN.matcher(filename);
 
 		if (matcher.find()) {
@@ -132,9 +115,12 @@ public class Tags {
 		return result;
 	}
 
-	public String toFilename(final SortedSet<Tag> tags) {
+	private static String toFilename(final Collection<Tag> tags) {
 		final StringBuilder path = new StringBuilder();
 
+		final Tag[] tagsAsArray = tags.toArray(new Tag[tags.size()]);
+		Arrays.sort(tagsAsArray, TagByKeyComparator.INSTANCE);
+
 		for (final Tag tag : tags) {
 			final String key = tag.getKey();
 			final String value = tag.getValue();
@@ -204,17 +190,17 @@ public class Tags {
 
 	public Tags subset(final List<String> groupByFields) {
 
-		Tags result = new Tags();
+		final TagsBuilder result = TagsBuilder.create();
 
 		for (final String field : groupByFields) {
 			final String value = getValue(field);
 
 			if (value != null) {
-				result = result.copyAdd(field, value);
+				result.add(field, value);
 			}
 		}
 
-		return result;
+		return result.build();
 	}
 
 	public boolean isEmpty() {
@@ -236,7 +222,7 @@ public class Tags {
 			}
 
 			result.append(tag.getKey());
-			result.append(":");
+			result.append("=");
 			result.append(tag.getValue());
 		}
 

pdb-api/src/main/java/org/lucares/pdb/api/TagsBuilder.java

@@ -0,0 +1,22 @@
+package org.lucares.pdb.api;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class TagsBuilder {
+
+	final List<Tag> tags = new ArrayList<>();
+
+	public static TagsBuilder create() {
+		return new TagsBuilder();
+	}
+
+	public TagsBuilder add(final String key, final String value) {
+		tags.add(new Tag(key, value));
+		return this;
+	}
+
+	public Tags build() {
+		return Tags.create(tags);
+	}
+}