如何比较 android 中的 two.db 文件格式？

Question

我正在为 android 制作一个应用程序，允许用户将.db 文件备份到他的设备中。 这些.db 文件是我的应用程序中由 sqlite 生成的数据库。 当用户恢复这些文件时，我想检查他是否没有编辑它并且它仍然是我的应用程序数据库格式（如下面的代码创建的）。 如需澄清，请发表评论。

String SQL_CREATE_FLIGHT_TABLE = "CREATE TABLE " + flightsEntery.TABLE_NAME + "("
                + flightsEntery.COLUMN_id + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                + flightsEntery.COLUMN_mat + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_ori + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_des + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_data + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_mil + " INTEGER NOT NULL DEFAULT 0, "
                + flightsEntery.COLUMN_Npou + " INTEGER NOT NULL DEFAULT 1, "
                + flightsEntery.COLUMN_IFRapp + " INTEGER NOT NULL, "
                + flightsEntery.COLUMN_Func + " INTEGER NOT NULL, "
                + flightsEntery.COLUMN_OBS + " TEXT, "
                + flightsEntery.COLUMN_Hdec + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Hpou + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Hsol + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Hhora + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Hdiu + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Hnot + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Hifr + " INTEGER NOT NULL DEFAULT 0, "
                + flightsEntery.COLUMN_Hvfr + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Hnav + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Sobcapota + " TEXT NOT NULL DEFAULT '00:00', "
                + flightsEntery.COLUMN_Hcorte + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_Hacc + " TEXT NOT NULL, "
                + flightsEntery.COLUMN_VooPara + " INTEGER NOT NULL DEFAULT 0, "
                + flightsEntery.COLUMN_VooReb + " INTEGER NOT NULL DEFAULT 0, "
                + flightsEntery.COLUMN_Trab + " INTEGER NOT NULL DEFAULT 0, "
                + flightsEntery.COLUMN_OrdyData + " INTERGER NOT NULL, "
                + flightsEntery.COLUMN_CivF + " INTEGER NOT NULL DEFAULT 0, "
                + flightsEntery.COLUMN_CivD + " INTEGER NOT NULL DEFAULT 0, "
                + flightsEntery.COLUMN_DiB + " INTEGER NOT NULL DEFAULT 0);";

我很乐意尝试任何想法，谢谢！

PS.：我不想比较数据库是否在每个细节上都相同，我只想知道列是否相同。

Answer 1

我相信您可以利用以下内容，它需要两个文件并根据查询比较两者之间的模式（sqlite_master），该查询通过名称、类型和 sql 列在两个组之间建立联合（如果它们相同，那么那里将是每组 2 个）并输出那些没有 2 行的行（即不匹配）。 如果返回的 Cursor 没有行，则 Schema 匹配。

public class CompareDBSchemas {

    public static boolean areDBSchemasEqual(File db1File, File db2File, boolean compareSizes) {
        boolean rv = true;
        if (!(db1File.exists() && db2File.exists())) return false;
        if (compareSizes) {
            if (db1File.length() != db2File.length()) return false;
        }
        SQLiteDatabase db1 = SQLiteDatabase.openDatabase(db1File.getPath(),null,SQLiteDatabase.OPEN_READWRITE);
        db1.execSQL("ATTACH '" +
                    db2File.getPath() +  "' AS other");

        /*
            WITH cte AS (SELECT * FROM main.sqlite_master UNION ALL SELECT * FROM other.sqlite_master)
            SELECT * FROM cte GROUP BY type,name,sql HAVING count() <> 2
         */
        Cursor csr = db1.rawQuery("WITH cte AS (" +
                "SELECT * FROM main.sqlite_master UNION ALL SELECT * FROM other.sqlite_master"  +
                        ") " +
                        "SELECT * FROM cte GROUP BY type,name,sql HAVING count() <> 2 ",
                null
        );
        if (csr.getCount() > 0) {
            rv = false;
        }
        csr.close();
        db1.close();
        return rv;
    }

    public static boolean areDBSchemasEqual(File db1File, File db2File) {
        return areDBSchemasEqual(db1File,db2File,false);
    }
}

• 请注意，上面有检测数据库大小差异的选项，这可能会检测更改的数据，而不仅仅是模式更改。

示例用法

下面演示了在创建 3 个数据库的情况下使用上述方法，第一个和第二个具有相同的架构，第三个不同（添加了额外的列）。

数据库Hlpr.java

public class DatabaseHlpr extends SQLiteOpenHelper {

    public static final String TABLE_NAME = "mytable";
    public static final String MYTABLE_COL_ID = BaseColumns._ID;
    public static final String MYTABLE_COL_COMMON = "common";
    public static final String MYTABLE_COL_SCHEMA1ONLY = "schema1only";

    private int mSchema;
    private SQLiteDatabase mDB;


    public DatabaseHlpr(@Nullable Context context, @Nullable String name, int schema) {
        super(context, name, null,1);
        this.mSchema = schema;
        mDB = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        switch (mSchema) {
            case 1:
                useSchema1(db);
                break;
            default:
                useSchema0(db);
        }
    }

    private void useSchema1(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "(" +
                MYTABLE_COL_ID + " INTEGER PRIMARY KEY, " +
                MYTABLE_COL_COMMON + " TEXT, " +
                MYTABLE_COL_SCHEMA1ONLY + " TEXT " +
                ")");
    }

    private void useSchema0(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "(" +
                MYTABLE_COL_ID + " INTEGER PRIMARY KEY, " +
                MYTABLE_COL_COMMON + " TEXT" +
                ")");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    static final String DB1NAME = "db1", DB2NAME = "db2", DB3NAME = "db3";
    DatabaseHlpr mDB1Hlpr, mDB2Hlpr, mDB3Hlpr;
    File db1File, db2File,db3File;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mDB1Hlpr = new DatabaseHlpr(this,DB1NAME,0);
        mDB2Hlpr = new DatabaseHlpr(this,DB2NAME,0);
        mDB3Hlpr = new DatabaseHlpr(this,DB3NAME,1);
        mDB1Hlpr.close();
        mDB2Hlpr.close();
        mDB3Hlpr.close();
        db1File = new File(this.getDatabasePath(DB1NAME).getPath());
        db2File = new File(this.getDatabasePath(DB2NAME).getPath());
        db3File = new File(this.getDatabasePath(DB3NAME).getPath());
        String result = " the same ";
        if (!CompareDBSchemas.areDBSchemasEqual(db1File,db2File,false)) {
            result = " NOT the same ";
        }
        Log.d("RESULTINFO",
                "Database Schemas are " + result +
                        " for " +
                        "\n\t" +db1File.getPath() +
                        "\n and \n\t" + db2File.getPath()
        );

        result = " the same ";
        if (!CompareDBSchemas.areDBSchemasEqual(db1File,db3File)) {
            result = " NOT the same ";
        }

        Log.d("RESULTINFO",
                "Database Schemas are " + result +
                        " for " +
                        "\n\t" +db1File.getPath() +
                        "\n and \n\t" + db3File.getPath()
        );
    }
}

• 请注意，以上是为了演示比较过程而编写的，因此文件检索简单方便。 它并非旨在反映如何检索文件。

结果：-

2019-10-27 07:19:23.688 28976-28976/aso.so58566618dbcompareschema D/RESULTINFO: Database Schemas are  the same  for 
        /data/user/0/aso.so58566618dbcompareschema/databases/db1
     and 
        /data/user/0/aso.so58566618dbcompareschema/databases/db2
2019-10-27 07:19:23.693 28976-28976/aso.so58566618dbcompareschema D/RESULTINFO: Database Schemas are  NOT the same  for 
        /data/user/0/aso.so58566618dbcompareschema/databases/db1
     and 
        /data/user/0/aso.so58566618dbcompareschema/databases/db3

额外的

如果您想要检查行数（插入或删除的数据）和实际数据（更新更改的数据）的能力，那么可以使用 CompareDBSchemas class 的以下改编：-

public class CompareDBSchemas {

    private static final String
            SQLITE_MASTER = "sqlite_master",
            SQLITE_MASTER_TYPE_COLUMN = "type",
            SQLITE_MASTER_NAME_COLUMN = "name",
            SQLITE_MASTER_SQL_COLUMN = "sql",
            SQLITE_MASTER_TABLE_TYPE = "table",
            SQLITE_SYSTEMTABLES = "sqlite_",
            ANDROID_METADATA = "android_metadata",
            CTE_NAME = "cte", MAIN_SCHEMA = "main", OTHER_SCHEMA = "other"
    ;

    public static boolean areDBSchemasEqual(File db1File, File db2File, boolean compareSizes, boolean compareRowCounts, boolean compareData) {
        boolean rv = true;
        if (!(db1File.exists() && db2File.exists())) return false;
        if (compareSizes) {
            if (db1File.length() != db2File.length()) return false;
        }
        SQLiteDatabase db1 = SQLiteDatabase.openDatabase(db1File.getPath(),null,SQLiteDatabase.OPEN_READWRITE);
        db1.beginTransaction();
        db1.execSQL("ATTACH '" +
                    db2File.getPath() +  "' AS " + OTHER_SCHEMA);

        /*
            WITH cte AS (SELECT * FROM sqlite_master UNION ALL SELECT * FROM sqlite_master)
            SELECT * FROM cte GROUP BY type,name,sql HAVING count() <> 2
         */
        Cursor csr = db1.rawQuery("WITH " + CTE_NAME + " AS (" +
                "SELECT * FROM " + MAIN_SCHEMA + "." + SQLITE_MASTER +
                        " UNION ALL " +
                        "SELECT * FROM " + OTHER_SCHEMA + "." + SQLITE_MASTER  +
                        ") " +
                        "SELECT * FROM " + CTE_NAME +
                        " GROUP BY " +
                        SQLITE_MASTER_TYPE_COLUMN + "," +
                        SQLITE_MASTER_NAME_COLUMN + "," +
                        SQLITE_MASTER_SQL_COLUMN +
                        " HAVING count() <> 2 ",
                null
        );
        if (csr.getCount() > 0) {
            rv = false;
        }
        if (compareRowCounts && rv) {
            csr = db1.rawQuery("SELECT * FROM main." + SQLITE_MASTER +
                    " WHERE " + SQLITE_MASTER_TYPE_COLUMN +
                    " = '" + SQLITE_MASTER_TABLE_TYPE +
                    "' AND (" + SQLITE_MASTER_NAME_COLUMN +
                    " NOT LIKE '" + SQLITE_SYSTEMTABLES +
                    "%' AND " + SQLITE_MASTER_NAME_COLUMN +
                    " <> '" + ANDROID_METADATA + "')",null);
            while(csr.moveToNext()) {
                if (
                        DatabaseUtils.queryNumEntries(db1,MAIN_SCHEMA +"." + csr.getString(csr.getColumnIndex(SQLITE_MASTER_NAME_COLUMN))) ==
                                DatabaseUtils.queryNumEntries(db1,OTHER_SCHEMA + "." + csr.getString(csr.getColumnIndex(SQLITE_MASTER_NAME_COLUMN)))
                ) continue;
                rv = false;
                break;
            }
        }
        if (compareData && rv) {
            csr.moveToPosition(-1);
            while (csr.moveToNext()) {
                if (
                        isTableDataTheSame(db1,csr.getString(csr.getColumnIndex(SQLITE_MASTER_NAME_COLUMN)))
                ) continue;
                rv = false;
                break;
            }
        }
        db1.endTransaction();
        csr.close();
        db1.close();
        return rv;
    }

    private static boolean isTableDataTheSame(SQLiteDatabase db, String table) {
        boolean rv = true;
        Cursor csr = db.rawQuery("PRAGMA table_info("+ table +")",null);
        StringBuilder columnConcat = new StringBuilder();
        while (csr.moveToNext()) {
            if (columnConcat.length() > 0) columnConcat.append("||");
            columnConcat.append(csr.getString(csr.getColumnIndex(SQLITE_MASTER_NAME_COLUMN)));
        }
        csr = db.rawQuery("WITH " + CTE_NAME +
                        " AS (" +
                        " SELECT " + columnConcat.toString() +
                        " AS comparison FROM " + MAIN_SCHEMA + "." + table +
                        " UNION ALL SELECT " + columnConcat.toString() + " FROM " + OTHER_SCHEMA + "." + table +
                        ") SELECT * FROM " + CTE_NAME +
                        " GROUP BY comparison HAVING count() <> 2",
                null
        );
        if (csr.getCount() > 0) {
            rv = false;
        }
        csr.close();
        return rv;
    }

    public static boolean areDBSchemasEqual(File db1File, File db2File) {
        return areDBSchemasEqual(db1File,db2File,false,false,false);
    }
}