Values are getting stored in .db-shm and .db-wal instead of actual SQLite file while INSERT in Android Studio

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英文:

Values are getting stored in .db-shm and .db-wal instead of actual SQLite file while INSERT in Android Studio

问题

我正在向存储在data>data>package_name>database文件中的现有数据库插入值。但是在插入值时,与其存储在data.db文件中,这些值会自动创建data.db-shmdata.db-wal文件,并保存在其中。我无法访问.db-shm.db-wal文件,但我可以从修改时间看出,每当我插入值时,这两个文件都会被修改,而不是实际的数据库文件。

以下是我的代码 -

MainActivity.java

package com.data.wifi;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import com.getcapacitor.BridgeActivity;
import com.getcapacitor.Plugin;

import java.util.ArrayList;

public class MainActivity extends BridgeActivity {

  DBHelper dbHelper = new DBHelper(this);

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    SQLiteDatabase db = dbHelper.getWritableDatabase();
    db.execSQL("INSERT INTO applogs VALUES ('7760','Tue Oct 27 2020','Values inserted Successfully' )");

    this.init(savedInstanceState, new ArrayList<Class<? extends Plugin>>() {{
      // Additional plugins you've installed go here
    }});
  }

  @Override
  public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.clear();
  }
}

DBHelper.java

package com.data.wifi;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DBHelper extends SQLiteOpenHelper {

  public static final int DATABASE_VERSION = 1;
  public static final String DATABASE_NAME = "data.db";
  public DBHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
  }

  @Override
  public void onCreate(SQLiteDatabase db) {  }

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

每当我尝试运行这段代码时,会创建两个具有相同数据库名称但不同扩展名(.db-shm和.db-shm)的文件,并且从修改时间来看,似乎一直在修改这两个文件。在此图片中,wifi.db是实际的数据库文件。但是会自动创建两个其他文件,看起来只有这两个文件会被修改

附注:在模拟器中,这段代码运行得非常完美,只有在我尝试在实际移动设备上运行时才会出现此问题。
编辑 - 当我在模拟器中运行代码时,值会被正确地插入到原始的数据库文件中,不会创建此类shm和wal文件。我认为这是一个问题,因为当我尝试提取我的数据库文件时,我在其中看不到我插入的值,数据库文件也没有被修改过。

英文:

I am inserting values to an Existing database stored in data&gt;data&gt;package_name&gt;databasefile. but while Inserting the values , Instead of getting stored in data.db file, the values are auto-creating data.db-shm and data.db-wal files , and getting saved in it. I cant access the .db-shm and .db-wal file , but I can see from the modification time , that whenever I insert values these two files are modified not the actual one.

Below are my code -

MainActivity.java
<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

package com.data.wifi;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import com.getcapacitor.BridgeActivity;
import com.getcapacitor.Plugin;

import java.util.ArrayList;

public class MainActivity extends BridgeActivity {

  DBHelper dbHelper = new DBHelper(this);

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    SQLiteDatabase db = dbHelper.getWritableDatabase();
    db.execSQL(&quot;INSERT INTO applogs VALUES (&#39;7760&#39;,&#39;Tue Oct 27 2020&#39;,&#39;Values inserted Successfully&#39; )&quot;);

    this.init(savedInstanceState, new ArrayList&lt;Class&lt;? extends Plugin&gt;&gt;() {{
      // Additional plugins you&#39;ve installed go here
      
    }});
  }

  @Override
  public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.clear();
  }
}

<!-- end snippet -->

DBHelper.java

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

package com.data.wifi;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DBHelper extends SQLiteOpenHelper {

  public static final int DATABASE_VERSION = 1;
  public static final String DATABASE_NAME = &quot;data.db&quot;;
  public DBHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
  }

  @Override
  public void onCreate(SQLiteDatabase db) {  }

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

<!-- end snippet -->

Whenever I am trying to run this code, two files are being created with same db name with different extensions (.db-shm and .db-shm) and it from the modification time , It looks like these two file are the ones getting modified all the time.In this pic wifi.db is the actual database file . but two other files are created automatically and looks like it is modifying only

PS- This code is working absolutely perfect in emulator, only when I try to run it on actual mobile device I am facing this issue.
Edit- When I run the code in an emulator , the values are inserted in the original dbfile properly, and no such shm and wal files are created there .
I am seeing this is an issue , because when I try to extract my db file , i dont see my inserted values there. neithr the db file looks modified

答案1

得分: 2

这种行为是正常的。这是预写日志工作的方式。如果您想要备份或将数据库传输到其他地方,
您可以执行

 pragma wal_checkpoint

以确保所有插入的值都存储在主要的(.db3)文件中。
或者您可以使用

pragma journal_mode=DELETE

参见这个问题:
https://stackoverflow.com/questions/51535178/how-to-manually-perform-checkpoint-in-sqlite-android

以及这个:
https://www.sqlite.org/pragma.html#pragma_journal_mode

英文:

This behavior is normal. This is the way write-ahead logging works. If you want to backup or transfer the database to some other place,
you can execute

 pragma wal_checkpoint

to ensure that all your inserted values are stored in the main (.db3) file.
Or you can use

pragma journal_mode=DELETE

See this question:
https://stackoverflow.com/questions/51535178/how-to-manually-perform-checkpoint-in-sqlite-android

and this:
https://www.sqlite.org/pragma.html#pragma_journal_mode

答案2

得分: 1

以下是翻译好的部分:

.db-wal 文件移动数据到 .db 文件,请使用 PRAGMA wal_checkpoint 命令,以下代码对我有效:

SQLiteDatabase db = this.getWritableDatabase();
String query = "PRAGMA wal_checkpoint(full)";

Cursor cursor = db.rawQuery(query, null);
if (cursor != null && cursor.moveToFirst()) {
    int a = cursor.getInt(0);
    int b = cursor.getInt(1);
    int c = cursor.getInt(2);
}
if (cursor != null) {
    cursor.close();
}
英文:

To move your data from .db-wal to .db use PRAGMA wal_checkpoint, following code worked for me -:

SQLiteDatabase db = this.getWritableDatabase();
String query = &quot;PRAGMA wal_checkpoint(full)&quot;;

Cursor cursor = db.rawQuery(query, null);
if (cursor != null &amp;&amp; cursor.moveToFirst()) {
    int a = cursor.getInt(0);
    int b = cursor.getInt(1);
    int c = cursor.getInt(2);

}
if (cursor != null) {
    cursor.close();
}

huangapple
  • 本文由 发表于 2020年10月27日 22:13:40
  • 转载请务必保留本文链接:https://go.coder-hub.com/64556335.html
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