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我是 SQLite 的新手，我正在尝试创建一个应用程序，用户可以在其中创建任务并向它们附加提醒。我正在使用SQLite数据库来保存这些项目。一切都很完美，现在我想实现一个全文搜索功能，我已经阅读SQLite了使用FTS4 VIRTUAL TABLE比普通搜索更好的方法的文档。

  • 所以为了保持虚拟表同步，我不得不使用触发器。但是调用后出现错误execSQL("//*Trigger code*//")

这是我的触发器（按照文档中提到的顺序使用它们）：

object SQLiteTriggerUtils {

    fun getBeforeDeleteTrigger(mainTable : String,
                               ftsTable : String,
                               rowId : Int?) : String {

        return "CREATE TRIGGER table_bd" +
                " BEFORE DELETE ON $mainTable" +
                " BEGIN DELETE FROM $ftsTable" +
                " WHERE docid=$rowId END;"
    }

    fun getBeforeUpdateTrigger(mainTable: String,
                               ftsTable: String,
                               rowId: Int?) : String {

        return "CREATE TRIGGER table_bu" +
                " BEFORE UPDATE ON $mainTable" +
                " BEGIN DELETE FROM $ftsTable" +
                " WHERE docid=$rowId END;"
    }

    fun getAfterUpdateTrigger(
        mainTable: String,
        ftsTable: String,
        rowId: Int?,
        updatedField: String,
        updatedValue: String?
    ) : String {

        return "CREATE TRIGGER table_au" +
                " AFTER UPDATE ON $mainTable" +
                " BEGIN INSERT INTO $ftsTable(docid, $updatedField)" +
                " VALUES($rowId, $updatedValue) END;"
    }

    fun getAfterInsertTrigger(
        mainTable: String,
        ftsTable: String,
        rowId: Int?,
        updatedField: String,
        updatedValue: String?
    ) : String {

        return "CREATE TRIGGER table_ai" +
                " AFTER INSERT ON $mainTable" +
                " BEGIN INSERT INTO $ftsTable(docid, $updatedField)" +
                " VALUES($rowId, $updatedValue) END;"
    }
}

这是我的数据库 onCreate() 方法：

override fun onCreate(db: SQLiteDatabase) {
        val CREATION_TABLE = ("CREATE TABLE $TABLE_NAME ( "
                + "$KEY_ID INTEGER PRIMARY KEY AUTOINCREMENT, "
                + "$KEY_LABEL TEXT, "
                + "$KEY_DESCRIPTION TEXT, "
                + "$KEY_IMPORTANCE INTEGER,"
                + "$KEY_LOGO INTEGER,"
                + "$KEY_TO_DO_DATE TEXT,"
                + "$KEY_CREATION_DATE TEXT)")
        val FTS_CREATION_TABLE = ("CREATE VIRTUAL TABLE $FTS_TABLE_NAME USING fts4 (content='$TABLE_NAME', $KEY_LABEL)")
        db.execSQL(CREATION_TABLE)
        db.execSQL(FTS_CREATION_TABLE)
    } 

override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) {
        db.execSQL("DROP TABLE IF EXISTS $TABLE_NAME")
        db.execSQL("DROP TABLE IF EXISTS $FTS_TABLE_NAME")
        onCreate(db)
    }

执行触发器 onDeleteItem() 方法的示例：

override fun deleteItem(itemId: Int): Boolean {
        var success : Boolean
        writableDatabase.apply {
            execSQL(SQLiteTriggerUtils.getBeforeDeleteTrigger(TABLE_NAME, FTS_TABLE_NAME, itemId))
            success = delete(TABLE_NAME, "id = ?", arrayOf(itemId.toString())) > 0
            close()
        }
        return success
    }

返回错误：

android.database.sqlite.SQLiteException: near "END": syntax error (Sqlite code 1): , while compiling: CREATE TRIGGER table_bd BEFORE DELETE ON todo_tasks BEGIN DELETE FROM fts_todo_tasks WHERE docid=1 END;, (OS error - 2:No such file or directory)
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1 回答 1

1

我认为您在纠正了在 BEGIN 和 END 之间用分号编码的触发操作的语法错误之后的问题：-

在此处输入图像描述

可能是您在知道值之前尝试添加触发器（可能不是这样，取决于代码）。

触发器是否是一个实体，例如构成架构的一部分的视图、表、索引等，因此需要一个唯一的名称。所以CREATE TRIGGER the_trigger_name ......要求the_trigger_name是唯一的。每次调用触发器的操作即将被执行时，您可能会尝试创建相同的触发器，然后由于触发器已经存在而失败。

您可以使用CREATE TRIGGER IF NOT EXISTS the_trigger_name ......，但是将使用现有的触发器。

因此，您可能想要DROP TRIGGER the_trigger_name在创建触发器之前。

然而！

说触发器的预期用途是在事件（UPDATE、DELETE 或 INSERT）发生时（实际上是紧接在之前或之后）自动执行类似的操作。因此，触发器可以访问导致触发器被操作（触发操作）的行的列。

如果触发操作是 INSERT，则可以使用 new.column 引用被插入行的列，并在触发操作中使用（在 BEGIN 和 END 之间指定的操作）。

如果触发操作是 DELETE，那么 old.column 可用于引用被删除行的列。

如果触发动作是 UPDATE，那么 new.column 和 old.column 都可以被引用。

  • 其中 .column 被相应的列替换。

因此，当文档说： -

一些用户可能希望使用数据库触发器来保持全文索引相对于存储在内容表中的文档集保持最新，而不是单独写入全文索引和内容表。例如，使用前面示例中的表：

CREATE TRIGGER t2_bu BEFORE UPDATE ON t2 BEGIN
  DELETE FROM t3 WHERE docid=old.rowid;
END;
CREATE TRIGGER t2_bd BEFORE DELETE ON t2 BEGIN
  DELETE FROM t3 WHERE docid=old.rowid;
END;

CREATE TRIGGER t2_au AFTER UPDATE ON t2 BEGIN
  INSERT INTO t3(docid, b, c) VALUES(new.rowid, new.b, new.c);
END;
CREATE TRIGGER t2_ai AFTER INSERT ON t2 BEGIN
  INSERT INTO t3(docid, b, c) VALUES(new.rowid, new.b, new.c);
END;

你会看到它使用old.docid和new.rowid

因此 old.docid 将是要删除的行的 docid 和 new.rowid 将是插入到$TABLE_NAME的行的 rowid 。因此，每个触发器只需要定义一次，因为它是通用的。

因此，我相信您可以使用：-

val TRG_BD = "trigger_bd" //<<<<<<<<<< ADDED >>>>>>>>>>
val TRG_BU = "trigger_bu" //<<<<<<<<<< ADDED >>>>>>>>>>
val TRG_AU = "trigger_au" //<<<<<<<<<< ADDED >>>>>>>>>>
val TRG_AI = "trigger_ai" //<<<<<<<<<< ADDED >>>>>>>>>>

override fun onCreate(db: SQLiteDatabase) {
    val CREATION_TABLE = ("CREATE TABLE $TABLE_NAME ( "
            + "$KEY_ID INTEGER PRIMARY KEY AUTOINCREMENT, "
            + "$KEY_LABEL TEXT, "
            + "$KEY_DESCRIPTION TEXT, "
            + "$KEY_IMPORTANCE INTEGER,"
            + "$KEY_LOGO INTEGER,"
            + "$KEY_TO_DO_DATE TEXT,"
            + "$KEY_CREATION_DATE TEXT)")
    val FTS_CREATION_TABLE = ("CREATE VIRTUAL TABLE $FTS_TABLE_NAME USING fts4 (content='$TABLE_NAME', $KEY_LABEL)")

    //<<<<<<<<<< ADDED FOLLOWING LINES  >>>>>>>>
    val BD_CREATION_TRIGGER = ("CREATE TRIGGER IF NOT EXISTS $TRG_BD " +
            "BEFORE DELETE ON $TABLE_NAME " +
            "BEGIN " +
            "DELETE FROM $FTS_TABLE_NAME " +
            "WHERE docid=old.rowid; " +
            "END;")
    val BU_CREATION_TRIGGER = ("CREATE TRIGGER IF NOT EXISTS $TRG_BU " +
            "BEFORE UPDATE ON $TABLE_NAME " +
            "BEGIN " +
            "DELETE FROM $FTS_TABLE_NAME " +
            "WHERE docid=old.rowid; " +
            "END;")
    val AU_CREATION_TRIGGER = ("CREATE TRIGGER IF NOT EXISTS $TRG_AU " +
            "AFTER UPDATE ON $TABLE_NAME " +
            "BEGIN " +
            "INSERT INTO $FTS_TABLE_NAME (docid, $KEY_LABEL) VALUES(new.$KEY_ID,new.$KEY_LABEL); " + //<<<<<<<< not sure $KEY_LABEL is correct column
            "END;")
    val AI_CREATION_TRIGGER = ("CREATE TRIGGER IF NOT EXISTS $TRG_AI " +
            "AFTER INSERT ON $TABLE_NAME " +
            "BEGIN " +
            "INSERT INTO $FTS_TABLE_NAME (docid, $KEY_LABEL) VALUES(new.$KEY_ID,new.$KEY_LABEL); " +
            "END;")
    //<<<<<<<<<< END OF ADDED LINES >>>>>>>>


    db.execSQL(CREATION_TABLE)
    db.execSQL(FTS_CREATION_TABLE)
    db.execSQL(BD_CREATION_TRIGGER) //<<<<<<<<<< ADDED >>>>>>>>>>
    db.execSQL(BU_CREATION_TRIGGER) //<<<<<<<<<< ADDED >>>>>>>>>>
    db.execSQL(AU_CREATION_TRIGGER) //<<<<<<<<<< ADDED >>>>>>>>>>
    db.execSQL(AI_CREATION_TRIGGER) //<<<<<<<<<< ADDED >>>>>>>>>>
}

override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) {
    db.execSQL("DROP TABLE IF EXISTS $TABLE_NAME")
    db.execSQL("DROP TABLE IF EXISTS $FTS_TABLE_NAME")
    db.execSQL("DROP TRIGGER IF EXISTS $TRG_BD") //<<<<<<<<<< ADDDED >>>>>>>>
    db.execSQL("DROP TRIGGER IF EXISTS $TRG_BU") //<<<<<<<<<< ADDDED >>>>>>>>
    db.execSQL("DROP TRIGGER IF EXISTS $TRG_AU") //<<<<<<<<<< ADDDED >>>>>>>>
    db.execSQL("DROP TRIGGER If EXISTS $TRG_AI") //<<<<<<<<<< ADDDED >>>>>>>>
    onCreate(db)
}

以上将替换（即不需要以下内容）：-

object SQLiteTriggerUtils {

    fun getBeforeDeleteTrigger(mainTable : String,
                               ftsTable : String,
                               rowId : Int?) : String {

        return "CREATE TRIGGER table_bd" +
                " BEFORE DELETE ON $mainTable" +
                " BEGIN DELETE FROM $ftsTable" +
                " WHERE docid=$rowId END;"
    }

    fun getBeforeUpdateTrigger(mainTable: String,
                               ftsTable: String,
                               rowId: Int?) : String {

        return "CREATE TRIGGER table_bu" +
                " BEFORE UPDATE ON $mainTable" +
                " BEGIN DELETE FROM $ftsTable" +
                " WHERE docid=$rowId END;"
    }

    fun getAfterUpdateTrigger(
        mainTable: String,
        ftsTable: String,
        rowId: Int?,
        updatedField: String,
        updatedValue: String?
    ) : String {

        return "CREATE TRIGGER table_au" +
                " AFTER UPDATE ON $mainTable" +
                " BEGIN INSERT INTO $ftsTable(docid, $updatedField)" +
                " VALUES($rowId, $updatedValue) END;"
    }

    fun getAfterInsertTrigger(
        mainTable: String,
        ftsTable: String,
        rowId: Int?,
        updatedField: String,
        updatedValue: String?
    ) : String {

        return "CREATE TRIGGER table_ai" +
                " AFTER INSERT ON $mainTable" +
                " BEGIN INSERT INTO $ftsTable(docid, $updatedField)" +
                " VALUES($rowId, $updatedValue) END;"
    }
}

此外，由于 TRIGGERS 会自动运行

override fun deleteItem(itemId: Int): Boolean {
        var success : Boolean
        writableDatabase.apply {
            execSQL(SQLiteTriggerUtils.getBeforeDeleteTrigger(TABLE_NAME, FTS_TABLE_NAME, itemId))
            success = delete(TABLE_NAME, "id = ?", arrayOf(itemId.toString())) > 0
            close()
        }
        return success
    }

可以替换为（其他人也一样）：-

override fun deleteItem(itemId: Int): Boolean {
        var success : Boolean
        writableDatabase.apply {
            success = delete(TABLE_NAME, "id = ?", arrayOf(itemId.toString())) > 0
            close()
        }
        return success
    }

注意以上为原则代码，未经测试或运行。因此，它可能包含错误。

  • 我还建议触发器名称，而不是使用 au（更新后）使用更具描述性的名称，因此命名约定没有那么严格（例如，你想在更新后使用另一个触发器？）。

工作示例

下面是一个演示触发器的工作示例（注意一点 Kotlin 经验，因此代码可能不是最好的）

数据库助手.kt

val DB_VERSION = 1;
val DB_NAME = "mydb"

public class DatabaseHelper(context: Context?) :

    SQLiteOpenHelper(context, DB_NAME, null, DB_VERSION) {

    val TABLE_NAME = "mytable"
    val FTS_TABLE_NAME = "myftstable"
    val TRG_BD = "trigger_bd"
    val TRG_BU = "trigger_bu"
    val TRG_AU = "trigger_au"
    val TRG_AI = "trigger_ai"
    val KEY_ID = "id";
    val KEY_LABEL = "label"
    val KEY_DESCRIPTION = "desctription"
    val KEY_IMPORTANCE = "importance";
    val KEY_LOGO = "logo";
    val KEY_TO_DO_DATE = "todo_date"
    val KEY_CREATION_DATE = "creation_date"



    override fun onCreate(db: SQLiteDatabase) {
        val CREATION_TABLE = ("CREATE TABLE $TABLE_NAME ( "
                + "$KEY_ID INTEGER PRIMARY KEY AUTOINCREMENT, "
                + "$KEY_LABEL TEXT, "
                + "$KEY_DESCRIPTION TEXT, "
                + "$KEY_IMPORTANCE INTEGER,"
                + "$KEY_LOGO INTEGER,"
                + "$KEY_TO_DO_DATE TEXT,"
                + "$KEY_CREATION_DATE TEXT)")
        val FTS_CREATION_TABLE = ("CREATE VIRTUAL TABLE $FTS_TABLE_NAME USING fts4 (content='$TABLE_NAME', $KEY_LABEL)")

        //<<<<<<<<<< ADDED FOLLOWING LINES  >>>>>>>>
        val BD_CREATION_TRIGGER = ("CREATE TRIGGER IF NOT EXISTS $TRG_BD " +
                "BEFORE DELETE ON $TABLE_NAME " +
                "BEGIN " +
                "DELETE FROM $FTS_TABLE_NAME " +
                "WHERE docid=old.$KEY_ID; " +
                "END;")
        val BU_CREATION_TRIGGER = ("CREATE TRIGGER IF NOT EXISTS $TRG_BU " +
                "BEFORE UPDATE ON $TABLE_NAME " +
                "BEGIN " +
                "DELETE FROM $FTS_TABLE_NAME " +
                "WHERE docid=old.$KEY_ID; " +
                "END;")
        val AU_CREATION_TRIGGER = ("CREATE TRIGGER IF NOT EXISTS $TRG_AU " +
                "AFTER UPDATE ON $TABLE_NAME " +
                "BEGIN " +
                "INSERT INTO $FTS_TABLE_NAME (docid, $KEY_LABEL) VALUES(new.$KEY_ID,new.$KEY_LABEL); " + //<<<<<<<< not sure $KEY_LABEL is correct column
                "END;")
        val AI_CREATION_TRIGGER = ("CREATE TRIGGER IF NOT EXISTS $TRG_AI " +
                "AFTER INSERT ON $TABLE_NAME " +
                "BEGIN " +
                "INSERT INTO $FTS_TABLE_NAME (docid, $KEY_LABEL) VALUES(new.$KEY_ID,new.$KEY_LABEL); " +
                "END;")
        db.execSQL(CREATION_TABLE)
        db.execSQL(FTS_CREATION_TABLE)
        db.execSQL(BD_CREATION_TRIGGER) //<<<<<<<<<< ADDED >>>>>>>>>>
        db.execSQL(BU_CREATION_TRIGGER) //<<<<<<<<<< ADDED >>>>>>>>>>
        db.execSQL(AU_CREATION_TRIGGER) //<<<<<<<<<< ADDED >>>>>>>>>>
        db.execSQL(AI_CREATION_TRIGGER) //<<<<<<<<<< ADDED >>>>>>>>>>
    }

    override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) {
        db.execSQL("DROP TABLE IF EXISTS $TABLE_NAME")
        db.execSQL("DROP TABLE IF EXISTS $FTS_TABLE_NAME")
        db.execSQL("DROP TRIGGER IF EXISTS $TRG_BD") //<<<<<<<<<< ADDDED >>>>>>>>
        db.execSQL("DROP TRIGGER IF EXISTS $TRG_BU") //<<<<<<<<<< ADDDED >>>>>>>>
        db.execSQL("DROP TRIGGER IF EXISTS $TRG_AU") //<<<<<<<<<< ADDDED >>>>>>>>
        db.execSQL("DROP TRIGGER If EXISTS $TRG_AI") //<<<<<<<<<< ADDDED >>>>>>>>
        onCreate(db)
    }

    fun insert(label: String, description: String, importance: Int, tododate: String, creationdate: String ) {

        val cv = ContentValues()
        cv.put(KEY_LABEL,label)
        cv.put(KEY_DESCRIPTION,description)
        cv.put(KEY_IMPORTANCE,importance)
        cv.put(KEY_LOGO,0)
        cv.put(KEY_TO_DO_DATE,tododate)
        cv.put(KEY_CREATION_DATE,creationdate)

        val db = this.writableDatabase
        val inserted = db.insert(TABLE_NAME, null, cv )
        Log.d("INSERT","INSERT result in an id of " + inserted + ".")
    }

    fun update(id: Long, label: String) {
        val cv = ContentValues()
        cv.put(KEY_LABEL,label)

        val db = this.writableDatabase
        val updated = db.update(TABLE_NAME,cv,"$KEY_ID =" + id,null)
        Log.d("UPDATED","UPDATE resulted in " + updated + " rows being updated.")
    }

    fun delete(id: Long) {
        val whereclause = "$KEY_ID=" + id

        val db = this.writableDatabase
        val deleted = db.delete(TABLE_NAME,whereclause,null)
        Log.d("DELETED","DELETE resulted in " + deleted + " rows being deleted.")
    }

    fun logtables() {
        val db = this.writableDatabase
        val csr1 = db.query(TABLE_NAME, null, null, null, null, null, null)
        dumpCursor(csr1)
        val csr2 = db.query(FTS_TABLE_NAME,null,null,null,null,null,null)
        dumpCursor(csr2)
        csr1.close()
        csr2.close()
    }
}

MainActivity.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val dbhelper = DatabaseHelper(this)
        dbhelper.insert("TEST001","Just Testing",10,"2019-01-01","2019-01-01")
        dbhelper.logtables()
        dbhelper.update(1,"001TEST")
        dbhelper.logtables()
        dbhelper.delete(1)
        dbhelper.logtables()
    }
}

结果（日志）

04-28 14:35:21.002 17810-17810/s.e.myapplication D/INSERT: INSERT result in an id of 1.
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@11697ce
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out: 0 {
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out:    id=1
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out:    label=TEST001
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out:    desctription=Just Testing
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out:    importance=10
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out:    logo=0
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out:    todo_date=2019-01-01
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out:    creation_date=2019-01-01
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out: }
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out: <<<<<
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@3396ef
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out: 0 {
04-28 14:35:21.002 17810-17810/s.e.myapplication I/System.out:    label=TEST001
04-28 14:35:21.003 17810-17810/s.e.myapplication I/System.out: }
04-28 14:35:21.003 17810-17810/s.e.myapplication I/System.out: <<<<<

即 FTS 已经为 TEST001 插入了一行

04-28 14:35:21.007 17810-17810/s.e.myapplication D/UPDATED: UPDATE resulted in 1 rows being updated.
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@9ce45fc
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out: 0 {
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out:    id=1
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out:    label=001TEST
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out:    desctription=Just Testing
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out:    importance=10
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out:    logo=0
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out:    todo_date=2019-01-01
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out:    creation_date=2019-01-01
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out: }
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out: <<<<<
04-28 14:35:21.007 17810-17810/s.e.myapplication I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@30ec485
04-28 14:35:21.008 17810-17810/s.e.myapplication I/System.out: 0 {
04-28 14:35:21.008 17810-17810/s.e.myapplication I/System.out:    label=001TEST
04-28 14:35:21.008 17810-17810/s.e.myapplication I/System.out: }
04-28 14:35:21.008 17810-17810/s.e.myapplication I/System.out: <<<<<

即 FTS 表已更新以反映 TEST001 更改为 001TEST

04-28 14:35:21.011 17810-17810/s.e.myapplication D/DELETED: DELETE resulted in 1 rows being deleted.
04-28 14:35:21.011 17810-17810/s.e.myapplication I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@10862da
04-28 14:35:21.011 17810-17810/s.e.myapplication I/System.out: <<<<<
04-28 14:35:21.011 17810-17810/s.e.myapplication I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@d4cb30b
04-28 14:35:21.011 17810-17810/s.e.myapplication I/System.out: <<<<<

从非fts表中删除后两者都是空的

于 2019-04-28T01:36:22.557 回答