使用contentProvider來進行SQlite transactions操作

項目需要在另外一個線程掃描數據並插入數據到數據庫中，一條一條插的話時間太慢，於是考慮到用SQlite的事務來進行提交，但是ContentProvider並沒有提供用於事務的API給上層，下面是我在網上找到的使用ContentProvider來進行SQlite transation的另一種方法。

 

 原文地址： http://eshyu.wordpress.com/2010/08/15/using-sqlite-transactions-with-your-contentprovider/

Using SQLite Transactions with your ContentProvider

Posted on August 15, 2010 by eshyu

In the world of databases, a transaction is a unit of work (including insertions, deletions, updates) that is Atomic, Consistent, Isolated, and Durable. By default in SQLite, each insertion is a transaction. And to preserve data integrity, SQLite will wait until data is stored on the disk before completing the transaction. So if you have a large data set that you’re trying to insert into your database, inserting each piece individually is going to seem extremely slow.

You want to use transactions, not just because they will increase the performance of your database operations. Because transactions are atomic, they will help you ensure your database is consistent. For example, if you need to process a large batch of instructions, then either everything happened correctly, or if something went wrong then that whole transaction failed (so it’s all or nothing).

By default the ContentResolver API provides a bulkInsert() method , but its not atomic and its slow as hell, so let’s override the bulkInsert() method in our ContentProvider.

view source print ?

01	public class YourProvider extends ContentProvider {

02	//..... define constants for the UriMatcher

03	public static final int EVENTS = 1 ;

04	public static final int FESTIVITIES = 2 ;

05

//....

06

07	private static final UriMatcher sUriMatcher = buildUriMatcher();

08	private YourDatabase mOpenHelper;

09

10

/**

11	* Creates the Uri matcher

12

*/

13	private static UriMatcher buildUriMatcher(){

14	final UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);

15	final String authority = YOUR_CONTENT_AUTHORITY;

16

17	//let the matcher match URIs with your defined constants

18	matcher.addURI(authority, "events" , EVENTS);

19	matcher.addURI(authority, "festivities" , FESTIVITIES);

20

//.....

21

22	return matcher;

23

}

24

25

@Override

26	public boolean onCreate() {

27	mOpenHelper = new YourDatabase(getContext());

28	return true ;

29

}

30

31

@Override

32	public String getType(Uri uri) {

33	final int match = sUriMatcher.match(uri);

34	switch (match){

35	case EVENTS:

36	return EVENTS.CONTENT_TYPE;

37	case FESTIVITIES:

38	return FESTIVITIES.CONTENT_TYPE;

39

//......

40

default :

41	throw new UnsupportedOperationException( "unknown: uri " + uri);

42

}

43

}

44

45

@Override

46	public int bulkInsert(Uri uri, ContentValues[] values) {

47	final SQLiteDatabase db = mOpenHelper.getWritableDatabase();

48	final int match = sUriMatcher.match(uri);

49	switch (match){

50	case EVENTS:

51	int numInserted= 0 ;

52	db.beginTransaction();

53

try {

54	//standard SQL insert statement, that can be reused

55	SQLiteStatement insert =

56	db.compileStatement( "insert into " + YOUR TABLE

57	+ "(" + COLUMN1 + "," + COLUMN2

58	+ "," + COLUMN3 + ")"

59	+ " values " + "(?,?,?" );

60

61	for (ContentValues value : values){

62	//bind the 1-indexed ?'s to the values specified

63	insert.bindString( 1 , value.getAsString(COLUMN1));

64	insert.bindString( 2 , value.getAsLong(COLUMN2));

65	insert.bindString( 3 , value.getAsString(COLUMN3));

66	insert.execute();

67

}

68	db.setTransactionSuccessful();

69	numInserted = values.length

70	} finally {

71	db.endTransaction();

72

}

73	return numInserted;

74

//....

75

default :

76	throw new UnsupportedOperationException( "unsupported uri: " + uri);

77

}}

78

79

}

So, for each ContentURI you are suppporting (each table in your db), write its respective bulkInsert case as above. And now you will witness an absolutely HUGE increase in performance (for me it cut the bulkInsert() time from 20 seconds to 1), and the return value of the bulkInsert() will now let you know if the transaction was successful or not. Also look here to see the transaction API.