FTS proof of concept

app/src/main/java/eu/faircode/email/FtsDbHelper.java

@@ -0,0 +1,103 @@
+package eu.faircode.email;
+
+/*
+    This file is part of FairEmail.
+
+    FairEmail is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    FairEmail is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2018-2020 by Marcel Bokhorst (M66B)
+*/
+
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.Cursor;
+import android.text.TextUtils;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import javax.mail.Address;
+
+import io.requery.android.database.sqlite.SQLiteDatabase;
+import io.requery.android.database.sqlite.SQLiteOpenHelper;
+
+public class FtsDbHelper extends SQLiteOpenHelper {
+    // https://www.sqlite.org/fts3.html
+    private static final int DATABASE_VERSION = 1;
+    private static final String DATABASE_NAME = "fts.db";
+
+    public FtsDbHelper(Context context) {
+        super(context, DATABASE_NAME, null, DATABASE_VERSION);
+    }
+
+    @Override
+    public void onCreate(SQLiteDatabase db) {
+        Log.i("FTS create");
+        db.execSQL("CREATE VIRTUAL TABLE `message` USING fts4(`time`, `address`, `subject`, `keyword`, `text`)");
+    }
+
+    @Override
+    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+        // Do nothing
+    }
+
+    void insert(EntityMessage message, String text) {
+        Log.i("FTS insert id=" + message.id + " subject=" + message.subject + " text=" + text);
+        List<Address> address = new ArrayList<>();
+        if (message.from != null)
+            address.addAll(Arrays.asList(message.from));
+        if (message.to != null)
+            address.addAll(Arrays.asList(message.to));
+        if (message.cc != null)
+            address.addAll(Arrays.asList(message.cc));
+
+        try (SQLiteDatabase db = getWritableDatabase()) {
+            try {
+                db.beginTransaction();
+
+                db.delete("message", "docid = ?", new Object[]{message.id});
+
+                ContentValues cv = new ContentValues();
+                cv.put("docid", message.id);
+                cv.put("time", message.received);
+                cv.put("address", MessageHelper.formatAddresses(address.toArray(new Address[0]), true, false));
+                cv.put("subject", message.subject == null ? "" : message.subject);
+                cv.put("keyword", TextUtils.join(", ", message.keywords));
+                cv.put("text", text);
+                db.insert("message", SQLiteDatabase.CONFLICT_FAIL, cv);
+
+                db.setTransactionSuccessful();
+            } finally {
+                db.endTransaction();
+            }
+        }
+    }
+
+    List<Long> match(String search) {
+        Log.i("FTS search=" + search);
+        List<Long> result = new ArrayList<>();
+        try (SQLiteDatabase db = getReadableDatabase()) {
+            try (Cursor cursor = db.query(
+                    "message", new String[]{"docid"},
+                    "message MATCH ?", new Object[]{search},
+                    null, null, "time DESC", null)) {
+                while (cursor != null && cursor.moveToNext())
+                    result.add(cursor.getLong(0));
+            }
+        }
+        Log.i("FTS result=" + result.size());
+        return result;
+    }
+}