Objectbox (#400)

* replaced SQLite/RoomDb with Objectbox for improved dictionary performance * SQLite words are automatically cleaned up when opening the Preferences * added protection against deleting dictionaries while loading other dictionaries * enabled adding words with apostrophes in Ukrainian * updated system requirements
2023-12-21 14:30:27 +02:00 · 2023-12-21 14:30:27 +02:00 · c02b4149e2
commit c02b4149e2
parent 7fb1ca7b5b
28 changed files with 693 additions and 691 deletions
--- a/README.md
+++ b/README.md
@ -18,8 +18,8 @@ or get the APK from the [Releases Section](https://github.com/sspanak/tt9/releas
 ## System Requirements
 - Android 4.4 or higher. _(Tested and confirmed on Android 4.4.2, 10 and 11)_
 - Free space:
-  - Minimum 30 Mb when not using Predictive mode and no dictionaries are loaded.
-  - Plenty of space per each enabled language in Predictive mode (25-100 Mb, depending on the word count).
+  - Minimum 40 Mb when not using Predictive mode and no dictionaries are loaded.
+  - Plenty of space per each enabled language in Predictive mode (50-400 Mb, depending on the word count).
 - A hardware keypad or a keyboard. For touchscreen-only devices, an on-screen keypad can be enabled in the Settings.

 _If you own a phone with Android 2.2 up to 4.4, please refer to the original version of Traditional T9 from 2016._
--- a/build.gradle
+++ b/build.gradle
@ -9,10 +9,13 @@ buildscript {
 	dependencies {
 		classpath 'com.android.tools.build:gradle:8.0.2'
 		classpath 'gradle.plugin.at.zierler:yaml-validator-plugin:1.5.0'
+		classpath("io.objectbox:objectbox-gradle-plugin:3.7.1")
 	}
 }
+
 apply plugin: 'com.android.application'
 apply plugin: 'at.zierler.yamlvalidator'
+apply plugin: "io.objectbox"

 apply from: 'gradle/scripts/constants.gradle'
 apply from: 'gradle/scripts/dictionary-tools.gradle'
@ -20,10 +23,6 @@ apply from: 'gradle/scripts/validate-languages.gradle'
 apply from: 'gradle/scripts/version-tools.gradle'

 configurations.configureEach {
-	// fixes 'duplicate class error', when using these combine: androidx.core:1.10.1, androidx.preference:1.2.0 and androidx.room:2.5.1
-	// see: https://stackoverflow.com/questions/75274720/a-failure-occurred-while-executing-appcheckdebugduplicateclasses/75315276#75315276
-	exclude group: 'org.jetbrains.kotlin', module: 'kotlin-stdlib-jdk8'
-
 	yamlValidator {
 		searchPaths = ['languages/definitions']
 	}
@ -32,8 +31,10 @@ configurations.configureEach {
 dependencies {
 	implementation 'androidx.core:core:1.10.1'
 	implementation 'androidx.preference:preference:1.2.1'
-	implementation 'androidx.room:room-runtime:2.5.2'
-	annotationProcessor 'androidx.room:room-compiler:2.5.2'
+
+	// fixes 'duplicate class error' when using "androidx.core" > 1.9.0
+	// see: https://stackoverflow.com/a/77323424
+	implementation(platform("org.jetbrains.kotlin:kotlin-bom:1.8.0"))
 }

 repositories {
--- a/objectbox-models/default.json
+++ b/objectbox-models/default.json
@ -0,0 +1,78 @@
+{
+  "_note1": "KEEP THIS FILE! Check it into a version control system (VCS) like git.",
+  "_note2": "ObjectBox manages crucial IDs for your object model. See docs for details.",
+  "_note3": "If you have VCS merge conflicts, you must resolve them according to ObjectBox docs.",
+  "entities": [
+    {
+      "id": "1:8686759156275895115",
+      "lastPropertyId": "9:148562041880145406",
+      "name": "Word",
+      "properties": [
+        {
+          "id": "1:7053654361616810150",
+          "name": "id",
+          "type": 6,
+          "flags": 1
+        },
+        {
+          "id": "2:1100881396300803213",
+          "name": "frequency",
+          "type": 5
+        },
+        {
+          "id": "3:3482550679443532896",
+          "name": "isCustom",
+          "type": 1
+        },
+        {
+          "id": "4:7366572918924354162",
+          "name": "langId",
+          "type": 5
+        },
+        {
+          "id": "5:2610279871343053806",
+          "name": "length",
+          "type": 5
+        },
+        {
+          "id": "6:5269773217039117329",
+          "name": "sequence",
+          "indexId": "1:2971223841434624317",
+          "type": 9,
+          "flags": 2048
+        },
+        {
+          "id": "7:3922044271904033267",
+          "name": "sequenceShort",
+          "indexId": "2:2641086768976362614",
+          "type": 2,
+          "flags": 8
+        },
+        {
+          "id": "8:1684236207225806285",
+          "name": "uniqueId",
+          "indexId": "3:5820769207826940948",
+          "type": 9,
+          "flags": 34848
+        },
+        {
+          "id": "9:148562041880145406",
+          "name": "word",
+          "type": 9
+        }
+      ],
+      "relations": []
+    }
+  ],
+  "lastEntityId": "1:8686759156275895115",
+  "lastIndexId": "3:5820769207826940948",
+  "lastRelationId": "0:0",
+  "lastSequenceId": "0:0",
+  "modelVersion": 5,
+  "modelVersionParserMinimum": 5,
+  "retiredEntityUids": [],
+  "retiredIndexUids": [],
+  "retiredPropertyUids": [],
+  "retiredRelationUids": [],
+  "version": 1
+}
--- a/src/io/github/sspanak/tt9/db/DictionaryDb.java
+++ b/src/io/github/sspanak/tt9/db/DictionaryDb.java
@ -1,11 +1,9 @@
 package io.github.sspanak.tt9.db;

 import android.content.Context;
-import android.database.sqlite.SQLiteConstraintException;
 import android.os.Handler;

 import androidx.annotation.NonNull;
-import androidx.sqlite.db.SimpleSQLiteQuery;

 import java.util.ArrayList;
 import java.util.List;
@ -13,24 +11,22 @@ import java.util.List;
 import io.github.sspanak.tt9.ConsumerCompat;
 import io.github.sspanak.tt9.Logger;
 import io.github.sspanak.tt9.db.exceptions.InsertBlankWordException;
-import io.github.sspanak.tt9.db.room.TT9Room;
-import io.github.sspanak.tt9.db.room.Word;
-import io.github.sspanak.tt9.db.room.WordList;
-import io.github.sspanak.tt9.db.room.WordsDao;
+import io.github.sspanak.tt9.db.objectbox.Word;
+import io.github.sspanak.tt9.db.objectbox.WordList;
+import io.github.sspanak.tt9.db.objectbox.WordStore;
 import io.github.sspanak.tt9.ime.TraditionalT9;
-import io.github.sspanak.tt9.languages.InvalidLanguageException;
 import io.github.sspanak.tt9.languages.Language;
 import io.github.sspanak.tt9.preferences.SettingsStore;
+import io.objectbox.exception.UniqueViolationException;

 public class DictionaryDb {
-	private static TT9Room dbInstance;
-
+	private static WordStore store;
 	private static final Handler asyncHandler = new Handler();

 	public static synchronized void init(Context context) {
-		if (dbInstance == null) {
+		if (store == null) {
 			context = context == null ? TraditionalT9.getMainContext() : context;
-			dbInstance = TT9Room.getInstance(context);
+			store = new WordStore(context);
 		}
 	}

@ -40,18 +36,18 @@ public class DictionaryDb {
 	}


-	private static TT9Room getInstance() {
+	private static WordStore getStore() {
 		init();
-		return dbInstance;
+		return store;
 	}


-	private static void printDebug(String tag, String title, String sequence, WordList words, long startTime) {
+	private static void printLoadDebug(String sequence, WordList words, long startTime) {
 		if (!Logger.isDebugLevel()) {
 			return;
 		}

-		StringBuilder debugText = new StringBuilder(title);
+		StringBuilder debugText = new StringBuilder("===== Word Matches =====");
 		debugText
 			.append("\n")
 			.append("Word Count: ").append(words.size())
@ -62,12 +58,12 @@ public class DictionaryDb {
 			debugText.append(" Sequence: ").append(sequence);
 		}

-		Logger.d(tag, debugText.toString());
+		Logger.d("loadWords", debugText.toString());
 	}


 	public static void runInTransaction(Runnable r) {
-		getInstance().runInTransaction(r);
+		getStore().runInTransaction(r);
 	}


@ -78,42 +74,66 @@ public class DictionaryDb {
 	 * This query will finish immediately, if there is nothing to do. It's safe to run it often.
 	 */
 	public static void normalizeWordFrequencies(SettingsStore settings) {
-		new Thread(() -> {
-			long time = System.currentTimeMillis();
+		final String LOG_TAG = "db.normalizeWordFrequencies";

-			int affectedRows = getInstance().wordsDao().normalizeFrequencies(
-				settings.getWordFrequencyNormalizationDivider(),
-				settings.getWordFrequencyMax()
-			);
+		new Thread(() -> {
+			for (int langId : getStore().getLanguages()) {
+				getStore().runInTransactionAsync(() -> {
+					try {
+						long start = System.currentTimeMillis();
+
+						if (getStore().getMaxFrequency(langId) < settings.getWordFrequencyMax()) {
+							return;
+						}
+
+						List<Word> words = getStore().getMany(langId);
+						if (words == null) {
+							return;
+						}
+
+						for (Word w : words) {
+							w.frequency /= settings.getWordFrequencyNormalizationDivider();
+						}
+
+						getStore().put(words);

 						Logger.d(
-				"db.normalizeWordFrequencies",
-				"Normalized " + affectedRows + " words in: " + (System.currentTimeMillis() - time) + " ms"
+							LOG_TAG,
+							"Normalized language: " + langId + ", " + words.size() + " words in: " + (System.currentTimeMillis() - start) + " ms"
 						);
+					} catch (Exception e) {
+						Logger.e(LOG_TAG, "Word normalization failed. " + e.getMessage());
+					} finally {
+						getStore().closeThreadResources();
+					}
+				});
+			}
 		}).start();
 	}


 	public static void areThereWords(ConsumerCompat<Boolean> notification, Language language) {
 		new Thread(() -> {
-			int langId = language != null ? language.getId() : -1;
-			notification.accept(getInstance().wordsDao().count(langId) > 0);
+			boolean areThere = getStore().count(language != null ? language.getId() : -1) > 0;
+			getStore().closeThreadResources();
+			notification.accept(areThere);
 		}).start();
 	}


-	public static void deleteWords(Runnable notification) {
-		deleteWords(notification, null);
-	}
-
-
-	public static void deleteWords(Runnable notification, ArrayList<Integer> languageIds) {
+	public static void deleteWords(Context context, Runnable notification) {
 		new Thread(() -> {
-			if (languageIds == null) {
-				getInstance().clearAllTables();
-			} else if (languageIds.size() > 0) {
-				getInstance().wordsDao().deleteByLanguage(languageIds);
+			getStore().destroy();
+			store = null;
+			init(context);
+			notification.run();
+		}).start();
 	}
+
+
+	public static void deleteWords(Runnable notification, @NonNull ArrayList<Integer> languageIds) {
+		new Thread(() -> {
+			getStore().removeMany(languageIds).closeThreadResources();
 			notification.run();
 		}).start();
 	}
@ -124,168 +144,128 @@ public class DictionaryDb {
 			throw new InsertBlankWordException();
 		}

-		Word dbWord = new Word();
-		dbWord.langId = language.getId();
-		dbWord.sequence = language.getDigitSequenceForWord(word);
-		dbWord.word = word;
-		dbWord.length = word.length();
-		dbWord.frequency = 1;
-
 		new Thread(() -> {
 			try {
-				if (getInstance().wordsDao().doesWordExist(dbWord.langId, dbWord.word) > 0) {
-					throw new SQLiteConstraintException("Word already exists.");
+				if (getStore().exists(language.getId(), word, language.getDigitSequenceForWord(word))) {
+					throw new UniqueViolationException("Word already exists");
 				}
-
-				getInstance().wordsDao().insert(dbWord);
-				getInstance().wordsDao().incrementFrequency(dbWord.langId, dbWord.word, dbWord.sequence);
+				getStore().put(Word.create(language, word, 1, true));
 				statusHandler.accept(0);
-			} catch (SQLiteConstraintException e) {
-				String msg = "Constraint violation when inserting a word: '" + dbWord.word + "' / sequence: '" + dbWord.sequence + "', for language: " + dbWord.langId
-					+ ". " + e.getMessage();
-				Logger.e("insertWord", msg);
+			} catch (UniqueViolationException e) {
+				String msg = "Skipping word: '" + word + "' for language: " + language.getId() + ", because it already exists.";
+				Logger.w("insertWord", msg);
 				statusHandler.accept(1);
 			} catch (Exception e) {
-				String msg = "Failed inserting word: '" + dbWord.word + "' / sequence: '" + dbWord.sequence	+ "', for language: " + dbWord.langId + ". " + e.getMessage();
+				String msg = "Failed inserting word: '" + word + "' for language: " + language.getId() + ". " + e.getMessage();
 				Logger.e("insertWord", msg);
 				statusHandler.accept(2);
+			} finally {
+				getStore().closeThreadResources();
 			}
 		}).start();
 	}


 	public static void upsertWordsSync(List<Word> words) {
-		getInstance().wordsDao().upsertMany(words);
+		getStore().put(words);
+		getStore().closeThreadResources();
 	}


-	public static void incrementWordFrequency(Language language, String word, String sequence) throws Exception {
-		Logger.d("incrementWordFrequency", "Incrementing priority of Word: " + word +" | Sequence: " + sequence);
-
-		if (language == null) {
-			throw new InvalidLanguageException();
-		}
-
-		// If both are empty, it is the same as changing the frequency of: "", which is simply a no-op.
-		if ((word == null || word.length() == 0) && (sequence == null || sequence.length() == 0)) {
+	public static void incrementWordFrequency(@NonNull Language language, @NonNull String word, @NonNull String sequence) {
+		// If any of these is empty, it is the same as changing the frequency of: "", which is simply a no-op.
+		if (word.length() == 0 || sequence.length() == 0) {
 			return;
 		}

-		// If one of them is empty, then this is an invalid operation,
-		// because a digit sequence exist for every word.
-		if (word == null || word.length() == 0 || sequence == null || sequence.length() == 0) {
-			throw new Exception("Cannot increment word frequency. Word: " + word + " | Sequence: " + sequence);
-		}
-
 		new Thread(() -> {
 			try {
-				int affectedRows = getInstance().wordsDao().incrementFrequency(language.getId(), word, sequence);
+				long start = System.currentTimeMillis();
+
+				Word dbWord = getStore().get(language.getId(), word, sequence);

 				// In case the user has changed the text case, there would be no match.
 				// Try again with the lowercase equivalent.
-				if (affectedRows == 0) {
-					String lowercaseWord = word.toLowerCase(language.getLocale());
-					affectedRows = getInstance().wordsDao().incrementFrequency(language.getId(), lowercaseWord, sequence);
-
-					Logger.d("incrementWordFrequency", "Attempting to increment frequency for lowercase variant: " + lowercaseWord);
+				if (dbWord == null) {
+					dbWord = getStore().get(language.getId(), word.toLowerCase(language.getLocale()), sequence);
 				}

-				Logger.d("incrementWordFrequency", "Affected rows: " + affectedRows);
+				if (dbWord == null) {
+					throw new Exception("No such word");
+				}
+
+				int max = getStore().getMaxFrequency(dbWord.langId, dbWord.sequence, dbWord.word);
+				if (dbWord.frequency <= max) {
+					dbWord.frequency = max + 1;
+					getStore().put(dbWord);
+					long time = System.currentTimeMillis() - start;
+
+					Logger.d(
+					"incrementWordFrequency",
+					"Incremented frequency of '" + dbWord.word + "' to: " + dbWord.frequency + ". Time: " + time + " ms"
+					);
+				} else {
+					long time = System.currentTimeMillis() - start;
+					Logger.d(
+						"incrementWordFrequency",
+						"'" + dbWord.word + "' is already the top word. Keeping frequency: " + dbWord.frequency + ". Time: " + time + " ms"
+					);
+				}
 			} catch (Exception e) {
 				Logger.e(
 					DictionaryDb.class.getName(),
-					"Failed incrementing word frequency. Word: " + word + " | Sequence: " + sequence + ". " + e.getMessage()
+					"Failed incrementing word frequency. Word: " + word + ". " + e.getMessage()
 				);
+			} finally {
+				getStore().closeThreadResources();
 			}
 		}).start();
 	}


 	/**
-	 * loadWordsExact
-	 * Loads words that match exactly the "sequence" and the optional "filter".
-	 * For example: "7655" gets "roll".
+	 * loadWords
+	 * Loads words matching and similar to a given digit sequence
+	 * For example: "7655" -> "roll" (exact match), but also: "rolled", "roller", "rolling", ...
+	 * and other similar.
 	 */
-	private static ArrayList<String> loadWordsExact(Language language, String sequence, String filter, int maximumWords) {
+	private static ArrayList<String> loadWords(Language language, String sequence, String filter, int minimumWords, int maximumWords) {
 		long start = System.currentTimeMillis();
-		WordList matches = new WordList(getInstance().wordsDao().getMany(
-			language.getId(),
-			maximumWords,
-			sequence,
-			filter == null || filter.equals("") ? null : filter
-		));

-		printDebug("loadWordsExact", "===== Exact Word Matches =====", sequence, matches, start);
+		WordList matches = getStore()
+			.getMany(language, sequence, filter, maximumWords)
+			.filter(sequence.length(), minimumWords);
+
+		getStore().closeThreadResources();
+		printLoadDebug(sequence, matches, start);
 		return matches.toStringList();
 	}


-	/**
-	 * loadWordsFuzzy
-	 * Loads words that start with "sequence" and optionally match the "filter".
-	 * For example: "7655" -> "roll", but also: "rolled", "roller", "rolling", ...
-	 */
-	private static ArrayList<String> loadWordsFuzzy(Language language, String sequence, String filter, int maximumWords) {
-		long start = System.currentTimeMillis();
+	public static void getWords(ConsumerCompat<ArrayList<String>> dataHandler, Language language, String sequence, String filter, int minimumWords, int maximumWords) {
+		final int minWords = Math.max(minimumWords, 0);
+		final int maxWords = Math.max(maximumWords, minWords);

-		// fuzzy queries are heavy, so we must restrict the search range as much as possible
-		boolean noFilter = (filter == null || filter.equals(""));
-		int maxWordLength = noFilter && sequence.length() <= 2 ? 5 : 1000;
-		String index = sequence.length() <= 2 ? WordsDao.indexShortWords : WordsDao.indexLongWords;
-		SimpleSQLiteQuery sql = TT9Room.getFuzzyQuery(index, language.getId(), maximumWords, sequence, sequence.length(), maxWordLength, filter);
-
-		WordList matches = new WordList(getInstance().wordsDao().getCustom(sql));
-
-		// In some cases, searching for words starting with "digitSequence" and limited to "maxWordLength" of 5,
-		// may yield too few results. If so, we expand the search range a bit.
-		if (noFilter && matches.size() < maximumWords) {
-			sql = TT9Room.getFuzzyQuery(
-				WordsDao.indexLongWords,
-				language.getId(),
-				maximumWords - matches.size(),
-				sequence,
-				5,
-				1000
-			);
-			matches.addAll(getInstance().wordsDao().getCustom(sql));
+		if (sequence == null || sequence.length() == 0) {
+			Logger.w("db.getWords", "Attempting to get words for an empty sequence.");
+			sendWords(dataHandler, new ArrayList<>());
+			return;
 		}

-		printDebug("loadWordsFuzzy", "~=~=~=~ Fuzzy Word Matches ~=~=~=~", sequence, matches, start);
-		return matches.toStringList();
+		if (language == null) {
+			Logger.w("db.getWords", "Attempting to get words for NULL language.");
+			sendWords(dataHandler, new ArrayList<>());
+			return;
+		}
+
+		new Thread(() -> sendWords(
+			dataHandler,
+			loadWords(language, sequence, filter, minWords, maxWords))
+		).start();
 	}


 	private static void sendWords(ConsumerCompat<ArrayList<String>> dataHandler, ArrayList<String> wordList) {
 		asyncHandler.post(() -> dataHandler.accept(wordList));
 	}
-
-
-	public static void getWords(ConsumerCompat<ArrayList<String>> dataHandler, Language language, String sequence, String filter, int minimumWords, int maximumWords) {
-		final int minWords = Math.max(minimumWords, 0);
-		final int maxWords = Math.max(maximumWords, minimumWords);
-
-		ArrayList<String> wordList = new ArrayList<>(maxWords);
-
-		if (sequence == null || sequence.length() == 0) {
-			Logger.w("db.getWords", "Attempting to get words for an empty sequence.");
-			sendWords(dataHandler, wordList);
-			return;
-		}
-
-		if (language == null) {
-			Logger.w("db.getWords", "Attempting to get words for NULL language.");
-			sendWords(dataHandler, wordList);
-			return;
-		}
-
-		new Thread(() -> {
-			wordList.addAll(loadWordsExact(language, sequence, filter, maxWords));
-
-			if (sequence.length() > 1 && wordList.size() < minWords) {
-				wordList.addAll(loadWordsFuzzy(language, sequence, filter, minWords - wordList.size()));
-			}
-
-			sendWords(dataHandler, wordList);
-		}).start();
-	}
 }
--- a/src/io/github/sspanak/tt9/db/DictionaryLoader.java
+++ b/src/io/github/sspanak/tt9/db/DictionaryLoader.java
@ -16,7 +16,7 @@ import io.github.sspanak.tt9.Logger;
 import io.github.sspanak.tt9.db.exceptions.DictionaryImportAbortedException;
 import io.github.sspanak.tt9.db.exceptions.DictionaryImportAlreadyRunningException;
 import io.github.sspanak.tt9.db.exceptions.DictionaryImportException;
-import io.github.sspanak.tt9.db.room.Word;
+import io.github.sspanak.tt9.db.objectbox.Word;
 import io.github.sspanak.tt9.languages.InvalidLanguageCharactersException;
 import io.github.sspanak.tt9.languages.InvalidLanguageException;
 import io.github.sspanak.tt9.languages.Language;
@ -80,7 +80,7 @@ public class DictionaryLoader {
 				currentFile = 0;
 				importStartTime = System.currentTimeMillis();

-				sendFileCount(languages.size());
+				sendStartMessage(languages.size());

 				// SQLite does not support parallel queries, so let's import them one by one
 				for (Language lang : languages) {
@ -155,8 +155,8 @@ public class DictionaryLoader {

 				Logger.e(
 					logTag,
-					"Failed loading dictionary: " + language.getDictionaryFile() +
-					" for language '" + language.getName() + "'. "
+					"Failed loading dictionary: " + language.getDictionaryFile()
+					+ " for language '" + language.getName() + "'. "
 					+ e.getMessage()
 				);
 			}
@ -164,7 +164,7 @@ public class DictionaryLoader {
 	}


-	private void importLetters(Language language) {
+	private void importLetters(Language language) throws InvalidLanguageCharactersException {
 		ArrayList<Word> letters = new ArrayList<>();

 		boolean isEnglish = language.getLocale().equals(Locale.ENGLISH);
@ -172,15 +172,7 @@ public class DictionaryLoader {
 		for (int key = 2; key <= 9; key++) {
 			for (String langChar : language.getKeyCharacters(key, false)) {
 				langChar = (isEnglish && langChar.equals("i")) ? langChar.toUpperCase(Locale.ENGLISH) : langChar;
-
-				Word word = new Word();
-				word.langId = language.getId();
-				word.frequency = 0;
-				word.length = 1;
-				word.sequence = String.valueOf(key);
-				word.word = langChar;
-
-				letters.add(word);
+				letters.add(Word.create(language, langChar, 0));
 			}
 		}

@ -189,7 +181,7 @@ public class DictionaryLoader {


 	private void importWords(Language language, String dictionaryFile) throws Exception {
-		sendProgressMessage(language, 0, 0);
+		sendProgressMessage(language, 1, 0);

 		long currentLine = 0;
 		long totalLines = getFileSize(dictionaryFile);
@ -200,7 +192,7 @@ public class DictionaryLoader {
 		for (String line; (line = br.readLine()) != null; currentLine++) {
 			if (loadThread.isInterrupted()) {
 				br.close();
-				sendProgressMessage(language, -1, 0);
+				sendProgressMessage(language, 0, 0);
 				throw new DictionaryImportAbortedException();
 			}

@ -209,7 +201,7 @@ public class DictionaryLoader {
 			int frequency = getFrequency(parts);

 			try {
-				dbWords.add(stringToWord(language, word, frequency));
+				dbWords.add(Word.create(language, word, frequency));
 			} catch (InvalidLanguageCharactersException e) {
 				br.close();
 				throw new DictionaryImportException(word, currentLine);
@ -222,6 +214,7 @@ public class DictionaryLoader {

 			if (totalLines > 0) {
 				int progress = (int) Math.floor(100.0 * currentLine / totalLines);
+				progress = Math.max(1, progress);
 				sendProgressMessage(language, progress, settings.getDictionaryImportProgressUpdateInterval());
 			}
 		}
@ -269,19 +262,7 @@ public class DictionaryLoader {
 	}


-	private Word stringToWord(Language language, String word, int frequency) throws InvalidLanguageCharactersException {
-		Word dbWord = new Word();
-		dbWord.langId = language.getId();
-		dbWord.frequency = frequency;
-		dbWord.length = word.length();
-		dbWord.sequence = language.getDigitSequenceForWord(word);
-		dbWord.word = word;
-
-		return dbWord;
-	}
-
-
-	private void sendFileCount(int fileCount) {
+	private void sendStartMessage(int fileCount) {
 		if (onStatusChange == null) {
 			Logger.w(logTag, "Cannot send file count without a status Handler. Ignoring message.");
 			return;
@ -289,6 +270,7 @@ public class DictionaryLoader {

 		Bundle progressMsg = new Bundle();
 		progressMsg.putInt("fileCount", fileCount);
+		progressMsg.putInt("progress", 1);
 		asyncHandler.post(() -> onStatusChange.accept(progressMsg));
 	}

--- a/src/io/github/sspanak/tt9/db/SQLWords.java
+++ b/src/io/github/sspanak/tt9/db/SQLWords.java
@ -0,0 +1,78 @@
+package io.github.sspanak.tt9.db;
+
+import android.app.Activity;
+import android.database.Cursor;
+import android.database.sqlite.SQLiteDatabase;
+
+import java.io.File;
+
+import io.github.sspanak.tt9.Logger;
+
+public class SQLWords {
+	private static final String DB_NAME = "t9dict.db";
+	private static final String TABLE_NAME = "words";
+
+	private static boolean isCompleted = false;
+
+	private final String LOG_TAG;
+	private final Activity activity;
+	private SQLiteDatabase db;
+
+	public SQLWords(Activity activity) {
+		this.activity = activity;
+
+		LOG_TAG = getClass().getSimpleName();
+	}
+
+	public void clear() {
+		if (isCompleted) {
+			return;
+		}
+
+		new Thread(() -> {
+			openDb();
+			if (areThereWords()) {
+				deleteAll();
+			}
+			closeDb();
+			isCompleted = true;
+		}).start();
+	}
+
+
+	private void openDb() {
+		try {
+			db = null;
+			File dbFile = activity.getDatabasePath(DB_NAME);
+			if (dbFile.exists()) {
+				db = SQLiteDatabase.openDatabase(dbFile.getAbsolutePath(), null, SQLiteDatabase.OPEN_READWRITE);
+			}
+		} catch (Exception e) {
+			Logger.d(LOG_TAG, "Assuming no SQL database, because of error while opening. " + e.getMessage());
+			db = null;
+		}
+	}
+
+
+	private void closeDb() {
+		if (db != null) {
+			db.close();
+		}
+	}
+
+
+	private boolean areThereWords() {
+		String sql = "SELECT COUNT(*) FROM (SELECT id FROM " + TABLE_NAME + " LIMIT 1)";
+		try (Cursor cursor = db.rawQuery(sql, null)) {
+			return cursor.moveToFirst() && cursor.getInt(0) > 0;
+		} catch (Exception e) {
+			Logger.d(LOG_TAG, "Assuming no words, because of query error. " + e.getMessage());
+			return false;
+		}
+	}
+
+	private void deleteAll() {
+		db.execSQL("DROP TABLE words");
+		Logger.d(LOG_TAG, "SQL Words cleaned successfully.");
+	}
+}
--- a/src/io/github/sspanak/tt9/db/migrations/DB10.java
+++ b/src/io/github/sspanak/tt9/db/migrations/DB10.java
@ -1,26 +0,0 @@
-package io.github.sspanak.tt9.db.migrations;
-
-import androidx.annotation.NonNull;
-import androidx.room.migration.Migration;
-import androidx.sqlite.db.SupportSQLiteDatabase;
-
-import io.github.sspanak.tt9.Logger;
-import io.github.sspanak.tt9.db.room.TT9Room;
-
-public class DB10 {
-	public static final Migration MIGRATION = new Migration(9, 10) {
-		@Override
-		public void migrate(@NonNull SupportSQLiteDatabase database) {
-			try {
-				database.beginTransaction();
-				database.execSQL(TT9Room.createShortWordsIndexQuery().getSql());
-				database.execSQL(TT9Room.createLongWordsIndexQuery().getSql());
-				database.setTransactionSuccessful();
-			} catch (Exception e) {
-				Logger.e("Migrate to DB10", "Migration failed. " + e.getMessage());
-			} finally {
-				database.endTransaction();
-			}
-		}
-	};
-}
--- a/src/io/github/sspanak/tt9/db/migrations/DB11.java
+++ b/src/io/github/sspanak/tt9/db/migrations/DB11.java
--- a/src/io/github/sspanak/tt9/db/migrations/DB6.java
+++ b/src/io/github/sspanak/tt9/db/migrations/DB6.java
@ -1,13 +0,0 @@
-package io.github.sspanak.tt9.db.migrations;
-
-import androidx.room.migration.Migration;
-import androidx.sqlite.db.SupportSQLiteDatabase;
-
-public class DB6 {
-	public static final Migration MIGRATION = new Migration(5, 6) {
-		@Override
-		public void migrate(SupportSQLiteDatabase database) {
-			database.execSQL("DROP TRIGGER IF EXISTS normalize_freq");
-		}
-	};
-}
--- a/src/io/github/sspanak/tt9/db/migrations/DB7.java
+++ b/src/io/github/sspanak/tt9/db/migrations/DB7.java
@ -1,90 +0,0 @@
-package io.github.sspanak.tt9.db.migrations;
-
-import android.content.Context;
-
-import androidx.annotation.NonNull;
-import androidx.room.migration.Migration;
-import androidx.sqlite.db.SupportSQLiteDatabase;
-
-import java.util.ArrayList;
-import java.util.Locale;
-
-import io.github.sspanak.tt9.languages.Language;
-import io.github.sspanak.tt9.languages.LanguageCollection;
-import io.github.sspanak.tt9.preferences.SettingsStore;
-
-public class DB7 {
-	private Context ctx;
-
-	public Migration getMigration(Context context) {
-		ctx = context;
-		return migration;
-	}
-
-	private int getNewLanguageId(int oldId) {
-		Language language;
-
-		switch (oldId) {
-			default:
-				return oldId;
-			case 1:
-				language = LanguageCollection.getByLocale(ctx, Locale.ENGLISH.toString());
-				break;
-			case 2:
-				language = LanguageCollection.getByLocale(ctx, "ru_RU");
-				break;
-			case 3:
-				language = LanguageCollection.getByLocale(ctx, Locale.GERMAN.toString());
-				break;
-			case 4:
-				language = LanguageCollection.getByLocale(ctx, Locale.FRENCH.toString());
-				break;
-			case 5:
-				language = LanguageCollection.getByLocale(ctx, Locale.ITALIAN.toString());
-				break;
-			case 6:
-				language = LanguageCollection.getByLocale(ctx, "uk_UA");
-				break;
-			case 7:
-				language = LanguageCollection.getByLocale(ctx, "bg_BG");
-				break;
-			case 8:
-				language = LanguageCollection.getByLocale(ctx, "nl_NL");
-				break;
-			case 9:
-				language = LanguageCollection.getByLocale(ctx, "es_ES");
-				break;
-		}
-
-		return language != null ? language.getId() : -1;
-	}
-
-	private final Migration migration = new Migration(6, 7) {
-		private void migrateSQL(SupportSQLiteDatabase database) {
-			for (int oldLangId = 1; oldLangId <= 9; oldLangId++) {
-				database.execSQL(
-					"UPDATE words " +
-					" SET lang = " + getNewLanguageId(oldLangId) +
-					" WHERE lang = " + oldLangId
-				);
-			}
-		}
-
-		private void migrateSettings() {
-			SettingsStore settings = new SettingsStore(ctx);
-
-			ArrayList<Integer> newLangIds = new ArrayList<>();
-			for (int langId : settings.getEnabledLanguageIds()) {
-				newLangIds.add(getNewLanguageId(langId));
-			}
-
-			settings.saveEnabledLanguageIds(newLangIds);
-		}
-
-		@Override
-		public void migrate(@NonNull SupportSQLiteDatabase database) {
-			migrateSQL(database);
-			migrateSettings();
-		}
-	};
-}
--- a/src/io/github/sspanak/tt9/db/migrations/DB8.java
+++ b/src/io/github/sspanak/tt9/db/migrations/DB8.java
@ -1,27 +0,0 @@
-package io.github.sspanak.tt9.db.migrations;
-
-import androidx.annotation.NonNull;
-import androidx.room.migration.Migration;
-import androidx.sqlite.db.SupportSQLiteDatabase;
-
-import io.github.sspanak.tt9.Logger;
-import io.github.sspanak.tt9.db.room.TT9Room;
-
-public class DB8 {
-	public static final Migration MIGRATION = new Migration(7, 8) {
-		@Override
-		public void migrate(@NonNull SupportSQLiteDatabase database) {
-			try {
-				database.beginTransaction();
-				database.execSQL("ALTER TABLE words ADD COLUMN len INTEGER NOT NULL DEFAULT 0");
-				database.execSQL("UPDATE words SET len = LENGTH(seq)");
-				database.execSQL(TT9Room.createShortWordsIndexQuery().getSql());
-				database.setTransactionSuccessful();
-			} catch (Exception e) {
-				Logger.e("Migrate to DB8", "Migration failed. " + e.getMessage());
-			} finally {
-				database.endTransaction();
-			}
-		}
-	};
-}
--- a/src/io/github/sspanak/tt9/db/migrations/DB9.java
+++ b/src/io/github/sspanak/tt9/db/migrations/DB9.java
@ -1,27 +0,0 @@
-package io.github.sspanak.tt9.db.migrations;
-
-import androidx.annotation.NonNull;
-import androidx.room.migration.Migration;
-import androidx.sqlite.db.SupportSQLiteDatabase;
-
-import io.github.sspanak.tt9.Logger;
-import io.github.sspanak.tt9.db.room.TT9Room;
-import io.github.sspanak.tt9.db.room.WordsDao;
-
-public class DB9 {
-	public static final Migration MIGRATION = new Migration(8, 9) {
-		@Override
-		public void migrate(@NonNull SupportSQLiteDatabase database) {
-			try {
-				database.beginTransaction();
-				database.execSQL("DROP INDEX " + WordsDao.indexLongWords);
-				database.execSQL(TT9Room.createLongWordsIndexQuery().getSql());
-				database.setTransactionSuccessful();
-			} catch (Exception e) {
-				Logger.e("Migrate to DB9", "Migration failed. " + e.getMessage());
-			} finally {
-				database.endTransaction();
-			}
-		}
-	};
-}
--- a/src/io/github/sspanak/tt9/db/objectbox/Word.java
+++ b/src/io/github/sspanak/tt9/db/objectbox/Word.java
@ -0,0 +1,48 @@
+package io.github.sspanak.tt9.db.objectbox;
+
+import androidx.annotation.NonNull;
+
+import io.github.sspanak.tt9.languages.InvalidLanguageCharactersException;
+import io.github.sspanak.tt9.languages.Language;
+import io.objectbox.annotation.ConflictStrategy;
+import io.objectbox.annotation.Entity;
+import io.objectbox.annotation.Id;
+import io.objectbox.annotation.Index;
+import io.objectbox.annotation.Unique;
+
+@Entity
+public class Word {
+	@Id public long id;
+	public int frequency;
+	public boolean isCustom;
+	public int langId;
+	public int length;
+	@Index public String sequence;
+	@Index public byte sequenceShort; // up to 2 digits
+	@Unique(onConflict = ConflictStrategy.REPLACE) public String uniqueId;
+	public String word;
+
+	public static Word create(@NonNull Language language, @NonNull String word, int frequency) throws InvalidLanguageCharactersException {
+		Word w = new Word();
+		w.frequency = frequency;
+		w.isCustom = false;
+		w.langId = language.getId();
+		w.length = word.length();
+		w.sequence = language.getDigitSequenceForWord(word);
+		w.sequenceShort = shrinkSequence(w.sequence);
+		w.uniqueId = (language.getId() + "-" + word);
+		w.word = word;
+
+		return w;
+	}
+
+	public static Word create(@NonNull Language language, @NonNull String word, int frequency, boolean isCustom) throws InvalidLanguageCharactersException {
+		Word w = create(language, word, frequency);
+		w.isCustom = isCustom;
+		return w;
+	}
+
+	public static Byte shrinkSequence(@NonNull String sequence) {
+		return Byte.parseByte(sequence.substring(0, Math.min(2, sequence.length())));
+	}
+}
--- a/src/io/github/sspanak/tt9/db/objectbox/WordList.java
+++ b/src/io/github/sspanak/tt9/db/objectbox/WordList.java
@ -1,15 +1,22 @@
-package io.github.sspanak.tt9.db.room;
+package io.github.sspanak.tt9.db.objectbox;

 import androidx.annotation.NonNull;

 import java.util.ArrayList;
 import java.util.List;

+
 public class WordList extends ArrayList<Word> {
-	public WordList(List<Word> words) {
+	public WordList() {
+		super();
+	}
+
+
+	public WordList(@NonNull List<Word> words) {
 		addAll(words);
 	}

+
 	@NonNull
 	@Override
 	public String toString() {
@ -26,6 +33,19 @@ public class WordList extends ArrayList<Word> {
 		return sb.toString();
 	}

+
+	@NonNull
+	public WordList filter(int minLength, int minWords) {
+		WordList filtered = new WordList();
+		for (int i = 0; i < size(); i++) {
+			if (get(i).length == minLength || filtered.size() < minWords) {
+				filtered.add(get(i));
+			}
+		}
+		return filtered;
+	}
+
+
 	@NonNull
 	public ArrayList<String> toStringList() {
 		ArrayList<String> strings = new ArrayList<>();
--- a/src/io/github/sspanak/tt9/db/objectbox/WordStore.java
+++ b/src/io/github/sspanak/tt9/db/objectbox/WordStore.java
@ -0,0 +1,208 @@
+package io.github.sspanak.tt9.db.objectbox;
+
+import android.content.Context;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import io.github.sspanak.tt9.Logger;
+import io.github.sspanak.tt9.languages.Language;
+import io.objectbox.Box;
+import io.objectbox.BoxStore;
+import io.objectbox.config.DebugFlags;
+import io.objectbox.query.Query;
+import io.objectbox.query.QueryBuilder;
+import io.objectbox.query.QueryCondition;
+
+public class WordStore {
+	private BoxStore boxStore;
+	private Box<Word> wordBox;
+
+	private Query<Word> longWordQuery;
+	private Query<Word> singleLetterQuery;
+
+
+	public WordStore(Context context) {
+		init(context);
+	}
+
+
+	private void init(Context context) {
+		boxStore = MyObjectBox.builder()
+			.androidContext(context.getApplicationContext())
+			.debugFlags(Logger.isDebugLevel() ? DebugFlags.LOG_QUERY_PARAMETERS : 0)
+			.build();
+
+		wordBox = boxStore.boxFor(Word.class);
+
+		longWordQuery = getLongWordQuery();
+		singleLetterQuery = getSingleLetterQuery();
+	}
+
+
+	private Query<Word> getLongWordQuery() {
+		return boxStore.boxFor(Word.class)
+			.query()
+				.equal(Word_.langId, 0)
+				.startsWith(Word_.sequence, "", QueryBuilder.StringOrder.CASE_SENSITIVE).parameterAlias("seq_start")
+				.lessOrEqual(Word_.sequence, "", QueryBuilder.StringOrder.CASE_SENSITIVE).parameterAlias("seq_end")
+				.equal(Word_.sequenceShort, 0)
+				.startsWith(Word_.word, "", QueryBuilder.StringOrder.CASE_SENSITIVE)
+			.order(Word_.length)
+			.orderDesc(Word_.frequency)
+			.build();
+	}
+
+	private Query<Word> getSingleLetterQuery() {
+		return wordBox
+			.query()
+				.equal(Word_.langId, 0)
+				.equal(Word_.sequenceShort, 0)
+				.startsWith(Word_.word, "", QueryBuilder.StringOrder.CASE_SENSITIVE)
+			.orderDesc(Word_.frequency)
+			.build();
+	}
+
+
+	public long count(int langId) {
+			try (Query<Word> query = wordBox.query(Word_.langId.equal(langId)).build()) {
+				return query.count();
+			} catch (Exception e) {
+				return 0;
+			}
+	}
+
+
+	public boolean exists(int langId, @NonNull String word, @NonNull String sequence) {
+		return get(langId, word, sequence) != null;
+	}
+
+
+	@Nullable
+	public Word get(int langId, @NonNull String word, @NonNull String sequence) {
+		QueryCondition<Word> where = Word_.langId.equal(langId)
+			.and(Word_.sequenceShort.equal(Word.shrinkSequence(sequence)))
+			.and(Word_.word.equal(word, QueryBuilder.StringOrder.CASE_SENSITIVE));
+
+		try (Query<Word> query = wordBox.query(where).build()) {
+			return query.findFirst();
+		}
+	}
+
+	@Nullable
+	public List<Word> getMany(int langId) {
+		try (Query<Word> query = wordBox.query(Word_.langId.equal(langId)).build()) {
+			return query.find();
+		}
+	}
+
+
+	@NonNull
+	public WordList getMany(Language language, @NonNull String sequence, @Nullable String filter, int maxWords) {
+		Query<Word> query;
+		if (sequence.length() < 2) {
+			singleLetterQuery.setParameter(Word_.sequenceShort, Byte.parseByte(sequence));
+			query = singleLetterQuery;
+		} else {
+			longWordQuery.setParameter(Word_.sequenceShort, Word.shrinkSequence(sequence));
+			longWordQuery.setParameter("seq_start", sequence);
+			longWordQuery.setParameter("seq_end", sequence + "99");
+			query = longWordQuery;
+		}
+
+		query.setParameter(Word_.langId, language.getId());
+
+		if (filter != null && !filter.equals("")) {
+			query.setParameter(Word_.word, filter);
+		} else {
+			query.setParameter(Word_.word, "");
+		}
+
+		return new WordList(query.find(0, maxWords));
+	}
+
+
+	public int[] getLanguages() {
+		try (Query<Word> query = wordBox.query().build()) {
+			return query.property(Word_.langId).distinct().findInts();
+		}
+	}
+
+
+	public int getMaxFrequency(int langId) {
+		return getMaxFrequency(langId, null, null);
+	}
+
+
+	public int getMaxFrequency(int langId, String sequence, String word) {
+		QueryCondition<Word> where = Word_.langId.equal(langId);
+
+		if (sequence != null && word != null) {
+			where = where.and(Word_.sequenceShort.equal(Word.shrinkSequence(sequence)))
+				.and(Word_.sequence.equal(sequence))
+				.and(Word_.word.notEqual(word));
+		}
+
+		try (Query<Word> query = wordBox.query(where).build()) {
+			long max = query.property(Word_.frequency).max();
+			return max == Long.MIN_VALUE ? 0 : (int)max;
+		}
+	}
+
+
+	public void put(@NonNull List<Word> words) {
+		wordBox.put(words);
+	}
+
+
+	public void put(@NonNull Word word) {
+		wordBox.put(word);
+	}
+
+
+	public WordStore removeMany(@NonNull ArrayList<Integer> languageIds) {
+		if (languageIds.size() > 0) {
+			try (Query<Word> query = wordBox.query(Word_.langId.oneOf(IntegerListToIntArray(languageIds))).build()) {
+				query.remove();
+			}
+		}
+
+		return this;
+	}
+
+
+	public void destroy() {
+		boxStore.closeThreadResources();
+		boxStore.close();
+		boxStore.deleteAllFiles();
+	}
+
+
+	public void runInTransaction(Runnable r) {
+		boxStore.runInTx(r);
+	}
+
+
+	public void runInTransactionAsync(Runnable action) {
+		boxStore.runInTxAsync(action, null);
+	}
+
+
+	public void closeThreadResources() {
+		boxStore.closeThreadResources();
+	}
+
+
+	private int[] IntegerListToIntArray(ArrayList<Integer> in) {
+		int[] out = new int[in.size()];
+		Iterator<Integer> iterator = in.iterator();
+		for (int i = 0; i < out.length; i++) {
+			out[i] = iterator.next();
+		}
+		return out;
+	}
+}
--- a/src/io/github/sspanak/tt9/db/room/TT9Room.java
+++ b/src/io/github/sspanak/tt9/db/room/TT9Room.java
@ -1,63 +0,0 @@
-package io.github.sspanak.tt9.db.room;
-
-import android.content.Context;
-
-import androidx.room.Database;
-import androidx.room.Room;
-import androidx.room.RoomDatabase;
-import androidx.sqlite.db.SimpleSQLiteQuery;
-
-import io.github.sspanak.tt9.db.migrations.DB10;
-import io.github.sspanak.tt9.db.migrations.DB11;
-import io.github.sspanak.tt9.db.migrations.DB6;
-import io.github.sspanak.tt9.db.migrations.DB7;
-import io.github.sspanak.tt9.db.migrations.DB8;
-import io.github.sspanak.tt9.db.migrations.DB9;
-
-@Database(version = 11, entities = Word.class, exportSchema = false)
-public abstract class TT9Room extends RoomDatabase {
-	public abstract WordsDao wordsDao();
-
-	public static synchronized TT9Room getInstance(Context context) {
-		return Room
-			.databaseBuilder(context, TT9Room.class, "t9dict.db")
-			.addMigrations(
-				DB6.MIGRATION,
-				new DB7().getMigration(context),
-				DB8.MIGRATION,
-				DB9.MIGRATION,
-				DB10.MIGRATION,
-				new DB11().getMigration(context)
-			)
-			.build();
-	}
-
-	public static SimpleSQLiteQuery getFuzzyQuery(String index, int langId, int limit, String sequence, int minWordLength, int maxWordLength, String word) {
-		String sql = "SELECT *" +
-			" FROM words INDEXED BY " + index + " " +
-			" WHERE 1" +
-			" AND lang = " + langId +
-			" AND len BETWEEN " + minWordLength + " AND " + maxWordLength +
-			" AND seq > " + sequence + " AND seq <= " + sequence + "99 " +
-			" ORDER BY len ASC, freq DESC " +
-			" LIMIT " + limit;
-
-		if (word != null) {
-			sql = sql.replace("WHERE 1", "WHERE 1 AND word LIKE '" + word.replace("'", "''") + "%'");
-		}
-
-		return new SimpleSQLiteQuery(sql);
-	}
-
-	public static SimpleSQLiteQuery getFuzzyQuery(String index, int langId, int limit, String sequence, int minWordLength, int maxWordLength) {
-		return getFuzzyQuery(index, langId, limit, sequence, minWordLength, maxWordLength, null);
-	}
-
-	public static SimpleSQLiteQuery createShortWordsIndexQuery() {
-		return new SimpleSQLiteQuery("CREATE INDEX IF NOT EXISTS " + WordsDao.indexShortWords + " ON words (lang ASC, len ASC, seq ASC)");
-	}
-
-	public static SimpleSQLiteQuery createLongWordsIndexQuery() {
-		return new SimpleSQLiteQuery("CREATE INDEX IF NOT EXISTS " + WordsDao.indexLongWords + " ON words (lang ASC, seq ASC, freq DESC)");
-	}
-}
--- a/src/io/github/sspanak/tt9/db/room/Word.java
+++ b/src/io/github/sspanak/tt9/db/room/Word.java
@ -1,33 +0,0 @@
-package io.github.sspanak.tt9.db.room;
-
-import androidx.room.ColumnInfo;
-import androidx.room.Entity;
-import androidx.room.Index;
-import androidx.room.PrimaryKey;
-
-@Entity(
-	indices = {
-		@Index(value = {"lang", "word"}, unique = true),
-		@Index(value = {"lang", "seq", "freq"}, orders = {Index.Order.ASC, Index.Order.ASC, Index.Order.DESC}),
-		@Index(value = {"lang", "len", "seq"}, orders = {Index.Order.ASC, Index.Order.ASC, Index.Order.ASC})
-	},
-	tableName = "words"
-)
-public class Word {
-	@PrimaryKey(autoGenerate = true)
-	public int id;
-
-	@ColumnInfo(name = "lang")
-	public int langId;
-
-	public String word;
-
-	@ColumnInfo(name = "seq")
-	public String sequence;
-
-	@ColumnInfo(name = "freq")
-	public int frequency;
-
-	@ColumnInfo(name = "len")
-	public int length;
-}
--- a/src/io/github/sspanak/tt9/db/room/WordsDao.java
+++ b/src/io/github/sspanak/tt9/db/room/WordsDao.java
@ -1,66 +0,0 @@
-package io.github.sspanak.tt9.db.room;
-
-import androidx.room.Dao;
-import androidx.room.Insert;
-import androidx.room.OnConflictStrategy;
-import androidx.room.Query;
-import androidx.room.RawQuery;
-import androidx.sqlite.db.SimpleSQLiteQuery;
-
-import java.util.ArrayList;
-import java.util.List;
-
-@Dao
-public interface WordsDao {
-	String indexLongWords = "index_words_lang_seq_freq";
-	String indexShortWords = "index_words_lang_len_seq";
-
-	@Query("SELECT COUNT(id) FROM words WHERE :langId < 0 OR lang = :langId")
-	int count(int langId);
-
-	@Query("DELETE FROM words WHERE lang IN(:langIds)")
-	void deleteByLanguage(ArrayList<Integer> langIds);
-
-	@Query("SELECT COUNT(id) FROM words WHERE lang = :langId AND word LIKE :word")
-	int doesWordExist(int langId, String word);
-
-	@Query(
-		"SELECT * " +
-		"FROM words " +
-		"WHERE " +
-			"lang = :langId " +
-			"AND seq = :sequence " +
-			"AND (:word IS NULL OR word LIKE :word || '%') " +
-		"ORDER BY freq DESC " +
-		"LIMIT :limit"
-	)
-	List<Word> getMany(int langId, int limit, String sequence, String word);
-
-	@RawQuery(observedEntities = Word.class)
-	List<Word> getCustom(SimpleSQLiteQuery query);
-
-	@Insert
-	void insert(Word word);
-
-	@Insert(onConflict = OnConflictStrategy.REPLACE)
-	void upsertMany(List<Word> words);
-
-	@Query(
-		"UPDATE words " +
-		"SET freq = (SELECT IFNULL(MAX(freq), 0) FROM words WHERE lang = :langId AND seq = :sequence AND word <> :word) + 1 " +
-		"WHERE lang = :langId AND word = :word AND seq = :sequence"
-	)
-	int incrementFrequency(int langId, String word, String sequence);
-
-	@Query(
-		"UPDATE words " +
-		"SET freq = freq / :normalizationDivider " +
-		"WHERE lang IN ( " +
-			"SELECT lang " +
-			"FROM words " +
-			"WHERE freq >= :maxFrequency " +
-			"GROUP BY lang" +
-		")"
-	)
-	int normalizeFrequencies(int normalizationDivider, int maxFrequency);
-}
--- a/src/io/github/sspanak/tt9/ime/TraditionalT9.java
+++ b/src/io/github/sspanak/tt9/ime/TraditionalT9.java
@ -355,7 +355,7 @@ public class TraditionalT9 extends KeyPadHandler {
 		cancelAutoAccept();
 		clearSuggestions();

-		String word = textField.getSurroundingWord();
+		String word = textField.getSurroundingWord(mLanguage);
 		if (word.isEmpty()) {
 			UI.toastLong(this, R.string.add_word_no_selection);
 		} else {
--- a/src/io/github/sspanak/tt9/ime/helpers/TextField.java
+++ b/src/io/github/sspanak/tt9/ime/helpers/TextField.java
@ -18,12 +18,16 @@ import java.util.regex.Pattern;

 import io.github.sspanak.tt9.Logger;
 import io.github.sspanak.tt9.ime.modes.InputMode;
+import io.github.sspanak.tt9.languages.Language;

 public class TextField {
 	public static final int IME_ACTION_ENTER = EditorInfo.IME_MASK_ACTION + 1;

 	private static final Pattern beforeCursorWordRegex = Pattern.compile("(\\w+)(?!\n)$");
 	private static final Pattern afterCursorWordRegex = Pattern.compile("^(?<!\n)(\\w+)");
+	private static final Pattern beforeCursorUkrainianRegex = Pattern.compile("([\\w']+)(?!\n)$");
+	private static final Pattern afterCursorUkrainianRegex = Pattern.compile("^(?<!\n)([\\w']+)");
+

 	public final InputConnection connection;
 	public final EditorInfo field;
@ -177,9 +181,20 @@ public class TextField {
 	 * getSurroundingWord
 	 * Returns the word next or around the cursor. Scanning length is up to 50 chars in each direction.
 	 */
-	@NonNull public String getSurroundingWord() {
-		Matcher before = beforeCursorWordRegex.matcher(getTextBeforeCursor());
-		Matcher after = afterCursorWordRegex.matcher(getTextAfterCursor());
+	@NonNull public String getSurroundingWord(Language language) {
+		Matcher before;
+		Matcher after;
+
+		if (language != null && language.isUkrainian()) {
+			// Ukrainian uses apostrophes as letters
+			before = beforeCursorUkrainianRegex.matcher(getTextBeforeCursor());
+			after = afterCursorUkrainianRegex.matcher(getTextAfterCursor());
+		} else {
+			// In other languages, special characters in words will cause automatic word break to fail,
+			// resulting in unexpected suggestions. Therefore, they are not allowed.
+			before = beforeCursorWordRegex.matcher(getTextBeforeCursor());
+			after = afterCursorWordRegex.matcher(getTextAfterCursor());
+		}

 		return (before.find() ? before.group(1) : "") + (after.find() ? after.group(1) : "");
 	}
--- a/src/io/github/sspanak/tt9/languages/Language.java
+++ b/src/io/github/sspanak/tt9/languages/Language.java
@ -167,6 +167,11 @@ public class Language {
 		return letters.contains("α");
 	}

+	public boolean isUkrainian() {
+		ArrayList<String> letters = getKeyCharacters(4, false);
+		return letters.contains("ї");
+	}
+
 	/* ************ utility ************ */

 	/**
--- a/src/io/github/sspanak/tt9/preferences/PreferencesActivity.java
+++ b/src/io/github/sspanak/tt9/preferences/PreferencesActivity.java
@ -17,6 +17,7 @@ import io.github.sspanak.tt9.Logger;
 import io.github.sspanak.tt9.R;
 import io.github.sspanak.tt9.db.DictionaryDb;
 import io.github.sspanak.tt9.db.DictionaryLoader;
+import io.github.sspanak.tt9.db.SQLWords;
 import io.github.sspanak.tt9.ime.helpers.GlobalKeyboardSettings;
 import io.github.sspanak.tt9.ime.helpers.InputModeValidator;
 import io.github.sspanak.tt9.preferences.helpers.Hotkeys;
@ -41,6 +42,7 @@ public class PreferencesActivity extends AppCompatActivity implements Preference
 		applyTheme();
 		Logger.enableDebugLevel(settings.getDebugLogsEnabled());

+		new SQLWords(this).clear();
 		DictionaryDb.init(this);
 		DictionaryDb.normalizeWordFrequencies(settings);

--- a/src/io/github/sspanak/tt9/preferences/items/ItemClickable.java
+++ b/src/io/github/sspanak/tt9/preferences/items/ItemClickable.java
@ -2,16 +2,20 @@ package io.github.sspanak.tt9.preferences.items;

 import androidx.preference.Preference;

+import java.util.ArrayList;
+import java.util.List;
+
 import io.github.sspanak.tt9.Logger;

-abstract class ItemClickable {
-	protected final int CLICK_DEBOUNCE_TIME = 250;
+abstract public class ItemClickable {
+	private final int CLICK_DEBOUNCE_TIME = 250;
 	private long lastClickTime = 0;

 	protected final Preference item;
+	private final ArrayList<ItemClickable> otherItems = new ArrayList<>();


-	ItemClickable(Preference item) {
+	public ItemClickable(Preference item) {
 		this.item = item;
 	}

@ -31,6 +35,29 @@ abstract class ItemClickable {
 	}


+	public ItemClickable setOtherItems(List<ItemClickable> others) {
+		otherItems.clear();
+		otherItems.addAll(others);
+		return this;
+	}
+
+
+	protected void disableOtherItems() {
+		for (ItemClickable i : otherItems) {
+			i.disable();
+		}
+
+	}
+
+
+	protected void enableOtherItems() {
+		for (ItemClickable i : otherItems) {
+			i.enable();
+		}
+
+	}
+
+
 	/**
 	 * debounceClick
 	 * Protection against faulty devices, that sometimes send two (or more) click events
--- a/src/io/github/sspanak/tt9/preferences/items/ItemLoadDictionary.java
+++ b/src/io/github/sspanak/tt9/preferences/items/ItemLoadDictionary.java
@ -35,11 +35,15 @@ public class ItemLoadDictionary extends ItemClickable {
 		this.settings = settings;

 		loader.setOnStatusChange(this::onLoadingStatusChange);
+		refreshStatus();
+	}

-		if (!progressBar.isCompleted() && !progressBar.isFailed()) {
-			changeToCancelButton();
+
+	public void refreshStatus() {
+		if (loader.isRunning()) {
+			setLoadingStatus();
 		} else {
-			changeToLoadButton();
+			setReadyStatus();
 		}
 	}

@ -49,12 +53,12 @@ public class ItemLoadDictionary extends ItemClickable {
 		item.setSummary(progressBar.getTitle() + " " + progressBar.getMessage());

 		if (progressBar.isCancelled()) {
-			changeToLoadButton();
+			setReadyStatus();
 		} else if (progressBar.isFailed()) {
-			changeToLoadButton();
+			setReadyStatus();
 			UI.toastFromAsync(context, progressBar.getMessage());
 		} else if (progressBar.isCompleted()) {
-			changeToLoadButton();
+			setReadyStatus();
 			UI.toastFromAsync(context, R.string.dictionary_loaded);
 		}
 	}
@ -65,23 +69,25 @@ public class ItemLoadDictionary extends ItemClickable {
 		ArrayList<Language> languages = LanguageCollection.getAll(context, settings.getEnabledLanguageIds());

 		try {
+			setLoadingStatus();
 			loader.load(languages);
-			changeToCancelButton();
 		} catch (DictionaryImportAlreadyRunningException e) {
 			loader.stop();
-			changeToLoadButton();
+			setReadyStatus();
 		}

 		return true;
 	}


-	public void changeToCancelButton() {
+	private void setLoadingStatus() {
+		disableOtherItems();
 		item.setTitle(context.getString(R.string.dictionary_cancel_load));
 	}


-	public void changeToLoadButton() {
+	private void setReadyStatus() {
+		enableOtherItems();
 		item.setTitle(context.getString(R.string.dictionary_load_title));
 		item.setSummary(progressBar.isFailed() || progressBar.isCancelled() ? progressBar.getMessage() : "");
 	}
--- a/src/io/github/sspanak/tt9/preferences/items/ItemTruncateAll.java
+++ b/src/io/github/sspanak/tt9/preferences/items/ItemTruncateAll.java
@ -14,42 +14,30 @@ public class ItemTruncateAll extends ItemClickable {

 	protected final PreferencesActivity activity;
 	protected final DictionaryLoader loader;
-	protected final ItemLoadDictionary loadItem;
-	protected ItemClickable otherTruncateItem;

-	public ItemTruncateAll(Preference item, ItemLoadDictionary loadItem, PreferencesActivity activity, DictionaryLoader loader) {
+
+	public ItemTruncateAll(Preference item, PreferencesActivity activity, DictionaryLoader loader) {
 		super(item);
 		this.activity = activity;
-		this.loadItem = loadItem;
 		this.loader = loader;
 	}


-	public ItemTruncateAll setOtherTruncateItem(ItemTruncateUnselected item) {
-		this.otherTruncateItem = item;
-		return this;
-	}
-
-
 	@Override
 	protected boolean onClick(Preference p) {
 		if (loader != null && loader.isRunning()) {
-			loader.stop();
-			loadItem.changeToLoadButton();
+			return false;
 		}

 		onStartDeleting();
-		DictionaryDb.deleteWords(this::onFinishDeleting);
+		DictionaryDb.deleteWords(activity.getApplicationContext(), this::onFinishDeleting);

 		return true;
 	}


 	protected void onStartDeleting() {
-		if (otherTruncateItem != null) {
-			otherTruncateItem.disable();
-		}
-		loadItem.disable();
+		disableOtherItems();
 		disable();
 		item.setSummary(R.string.dictionary_truncating);
 	}
@ -57,10 +45,7 @@ public class ItemTruncateAll extends ItemClickable {

 	protected void onFinishDeleting() {
 		activity.runOnUiThread(() -> {
-			if (otherTruncateItem != null) {
-				otherTruncateItem.enable();
-			}
-			loadItem.enable();
+			enableOtherItems();
 			item.setSummary("");
 			enable();
 			UI.toastFromAsync(activity, R.string.dictionary_truncated);
--- a/src/io/github/sspanak/tt9/preferences/items/ItemTruncateUnselected.java
+++ b/src/io/github/sspanak/tt9/preferences/items/ItemTruncateUnselected.java
@ -18,23 +18,17 @@ public class ItemTruncateUnselected extends ItemTruncateAll {
 	private final SettingsStore settings;


-	public ItemTruncateUnselected(Preference item, ItemLoadDictionary loadItem, PreferencesActivity context, SettingsStore settings, DictionaryLoader loader) {
-		super(item, loadItem, context, loader);
+	public ItemTruncateUnselected(Preference item, PreferencesActivity context, SettingsStore settings, DictionaryLoader loader) {
+		super(item, context, loader);
 		this.settings = settings;
 	}


-	public ItemTruncateUnselected setOtherTruncateItem(ItemTruncateAll otherTruncateItem) {
-		this.otherTruncateItem = otherTruncateItem;
-		return this;
-	}
-

 	@Override
 	protected boolean onClick(Preference p) {
 		if (loader != null && loader.isRunning()) {
-			loader.stop();
-			loadItem.changeToLoadButton();
+			return false;
 		}

 		ArrayList<Integer> unselectedLanguageIds = new ArrayList<>();
--- a/src/io/github/sspanak/tt9/preferences/screens/DictionariesScreen.java
+++ b/src/io/github/sspanak/tt9/preferences/screens/DictionariesScreen.java
@ -1,5 +1,7 @@
 package io.github.sspanak.tt9.preferences.screens;

+import java.util.Arrays;
+
 import io.github.sspanak.tt9.R;
 import io.github.sspanak.tt9.preferences.PreferencesActivity;
 import io.github.sspanak.tt9.preferences.items.ItemLoadDictionary;
@ -8,6 +10,10 @@ import io.github.sspanak.tt9.preferences.items.ItemTruncateAll;
 import io.github.sspanak.tt9.preferences.items.ItemTruncateUnselected;

 public class DictionariesScreen extends BaseScreenFragment {
+	private ItemLoadDictionary loadItem;
+	private ItemTruncateUnselected deleteItem;
+	private ItemTruncateAll truncateItem;
+
 	public DictionariesScreen() { init(); }
 	public DictionariesScreen(PreferencesActivity activity) { init(activity); }

@ -23,31 +29,35 @@ public class DictionariesScreen extends BaseScreenFragment {
 		);
 		multiSelect.populate().enableValidation();

-		ItemLoadDictionary loadItem = new ItemLoadDictionary(
+		loadItem = new ItemLoadDictionary(
 			findPreference(ItemLoadDictionary.NAME),
 			activity,
 			activity.settings,
 			activity.getDictionaryLoader(),
 			activity.getDictionaryProgressBar()
 		);
-		loadItem.enableClickHandler();

-		ItemTruncateAll truncateItem = new ItemTruncateAll(
-			findPreference(ItemTruncateAll.NAME),
-			loadItem,
-			activity,
-			activity.getDictionaryLoader()
-		);
-
-		ItemTruncateUnselected truncateSelectedItem = new ItemTruncateUnselected(
+		deleteItem = new ItemTruncateUnselected(
 			findPreference(ItemTruncateUnselected.NAME),
-			loadItem,
 			activity,
 			activity.settings,
 			activity.getDictionaryLoader()
 		);

-		truncateItem.setOtherTruncateItem(truncateSelectedItem).enableClickHandler();
-		truncateSelectedItem.setOtherTruncateItem(truncateItem).enableClickHandler();
+		truncateItem = new ItemTruncateAll(
+			findPreference(ItemTruncateAll.NAME),
+			activity,
+			activity.getDictionaryLoader()
+		);
+
+		loadItem.setOtherItems(Arrays.asList(truncateItem, deleteItem)).enableClickHandler();
+		deleteItem.setOtherItems(Arrays.asList(truncateItem, loadItem)).enableClickHandler();
+		truncateItem.setOtherItems(Arrays.asList(deleteItem, loadItem)).enableClickHandler();
+	}
+
+	@Override
+	public void onResume() {
+		super.onResume();
+		loadItem.refreshStatus();
 	}
 }
--- a/src/io/github/sspanak/tt9/ui/DictionaryLoadingBar.java
+++ b/src/io/github/sspanak/tt9/ui/DictionaryLoadingBar.java
@ -106,6 +106,7 @@ public class DictionaryLoadingBar {
 	public void show(Context context, Bundle data) {
 		String error = data.getString("error", null);
 		int fileCount = data.getInt("fileCount", -1);
+		int progress = data.getInt("progress", -1);

 		if (error != null) {
 			hasFailed = true;
@ -116,10 +117,12 @@ public class DictionaryLoadingBar {
 				data.getLong("fileLine", -1),
 				data.getString("word", "")
 			);
-		} else if (fileCount > -1) {
-			setFileCount(fileCount);
-		} else  {
+		} else if (progress >= 0) {
 			hasFailed = false;
+			if (fileCount >= 0) {
+				setFileCount(fileCount);
+			}
+
 			showProgress(
 				context,
 				data.getLong("time", 0),
@ -143,7 +146,7 @@ public class DictionaryLoadingBar {


 	private void showProgress(Context context, long time, int currentFile, int currentFileProgress, int languageId) {
-		if (currentFileProgress < 0) {
+		if (currentFileProgress <= 0) {
 			hide();
 			isStopped = true;
 			title = "";