harmony 鸿蒙Database Backup and Restoration

2023-06-24
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Database Backup and Restoration

When to Use

You may need to restore a database in any of the following cases:

An important operation being performed by an application is interrupted.

The database is unavailable due to data loss or corruption, or dirty data.

Both KV stores and RDB stores support database backup and restoration. In addition, KV stores allow you to delete database backups to release local storage space.

Backing Up, Restoring, and Deleting a KV Store

You can use backup() to back up a KV store, use restore() to restore a KV store, and use deletebackup() to delete a KV store backup file. For details about the APIs, see Distributed KV Store.

Create a KV store.

(1) Create a kvManager instance.

(2) Set database parameters.

(3) Create a kvStore instance.

   import distributedKVStore from '@ohos.data.distributedKVStore';
   import { BusinessError } from '@ohos.base';
   
   let kvManager: distributedKVStore.KVManager;
   let kvStore: distributedKVStore.SingleKVStore|undefined = undefined;
   let context = getContext(this);
   const kvManagerConfig: distributedKVStore.KVManagerConfig = {
     context: context,
     bundleName: 'com.example.datamanagertest'
   }
   try {
     kvManager = distributedKVStore.createKVManager(kvManagerConfig);
     console.info('Succeeded in creating KVManager.');
     try {
       const options: distributedKVStore.Options = {
         createIfMissing: true,
         encrypt: true,
         backup: false,
         autoSync: true,
         kvStoreType: distributedKVStore.KVStoreType.SINGLE_VERSION,
         securityLevel: distributedKVStore.SecurityLevel.S1
       };
       kvManager.getKVStore<distributedKVStore.SingleKVStore>('storeId', options, (err, store: distributedKVStore.SingleKVStore) => {
         if (err) {
           console.error(`Failed to get KVStore. Code:${err.code},message:${err.message}`);
           return;
         }
         console.info('Succeeded in getting KVStore.');
         kvStore = store;
       });
     } catch (e) {
       let error = e as BusinessError;
       console.error(`An unexpected error occurred. Code:${error.code},message:${error.message}`);
     }
   } catch (e) {
     let error = e as BusinessError;
     console.error(`Failed to create KVManager. Code:${error.code},message:${error.message}`);
   }
   
   if (kvStore !== undefined) {
     kvStore = kvStore as distributedKVStore.SingleKVStore;
     // Perform subsequent operations.
     //...
   }

Use put() to insert data to the KV store.

   const KEY_TEST_STRING_ELEMENT = 'key_test_string';
   const VALUE_TEST_STRING_ELEMENT = 'value_test_string';
   try {
     kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT, (err) => {
       if (err !== undefined) {
         console.error(`Fail to put data. Code:${err.code},message:${err.message}`);
         return;
       }
       console.info('Succeeded in putting data.');
     });
   } catch (e) {
     let error = e as BusinessError;
     console.error(`An unexpected error occurred. Code:${error.code},message:${error.message}`);
   }

Use backup() to back up the KV store.

   let file = 'BK001';
   try {
     kvStore.backup(file, (err) => {
       if (err) {
         console.error(`Fail to backup data.code:${err.code},message:${err.message}`);
       } else {
         console.info('Succeeded in backupping data.');
       }
     });
   } catch (e) {
     let error = e as BusinessError;
     console.error(`An unexpected error occurred. Code:${error.code},message:${error.message}`);
   }

Use delete() to delete data to simulate unexpected deletion or data tampering.

   try {
     kvStore.delete(KEY_TEST_STRING_ELEMENT, (err) => {
       if (err !== undefined) {
         console.error(`Fail to delete data. Code:${err.code},message:${err.message}`);
         return;
       }
       console.info('Succeeded in deleting data.');
     });
   } catch (e) {
     let error = e as BusinessError;
     console.error(`An unexpected error occurred. Code:${error.code},message:${error.message}`);
   }

Use restore() to restore the KV store.

   let file = 'BK001';
   try {
     kvStore.restore(file, (err) => {
       if (err) {
         console.error(`Fail to restore data. Code:${err.code},message:${err.message}`);
       } else {
         console.info('Succeeded in restoring data.');
       }
     });
   } catch (e) {
     let error = e as BusinessError;
     console.error(`An unexpected error occurred. Code:${error.code},message:${error.message}`);
   }

Use deleteBackup() to delete the backup file to release storage space.

   let files = ['BK001'];
   try {
     kvStore.deleteBackup(files).then((data) => {
       console.info(`Succeed in deleting Backup. Data:filename is ${data[0]},result is ${data[1]}.`);
     }).catch((err: BusinessError) => {
       console.error(`Fail to delete Backup. Code:${err.code},message:${err.message}`);
     })
   } catch (e) {
     let error = e as BusinessError;
     console.error(`An unexpected error occurred. Code:${error.code},message:${error.message}`);
   }

Backing Up and Restoring an RDB Store

You can use backup() to back up an RDB store, and use restore() to restore an RDB store. For details about the APIs, see RDB Store.

Use getRdbStore() to create an RDB store.

   import relationalStore from '@ohos.data.relationalStore';
   import { BusinessError } from '@ohos.base';
   
   let store: relationalStore.RdbStore|undefined = undefined;

   let context = getContext(this);

   const STORE_CONFIG: relationalStore.StoreConfig = {
     name: 'RdbTest.db',
     securityLevel: relationalStore.SecurityLevel.S1
   };
   relationalStore.getRdbStore(context, STORE_CONFIG, (err, rdbStore) => {
     store = rdbStore;
     if (err) {
       console.error(`Failed to get RdbStore. Code:${err.code},message:${err.message}`);
       return;
     }
     store.executeSql('CREATE TABLE IF NOT EXISTS EMPLOYEE (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT NOT NULL, AGE INTEGER, SALARY REAL, CODES BLOB)', (err) => {
     })
     console.info('Succeeded in getting RdbStore.');
   })

Use insert() to insert data to the RDB store.

   import { ValuesBucket } from '@ohos.data.ValuesBucket';

   let key1 = "NAME";
   let key2 = "AGE";
   let key3 = "SALARY";
   let key4 = "CODES";
   let value1 = "Rose";
   let value2 = 22;
   let value3 = 200.5;
   let value4 = new Uint8Array([1, 2, 3, 4, 5]);
   const valueBucket: ValuesBucket = {
     key1: value1,
     key2: value2,
     key3: value3,
     key4: value4,
   };
   if(store != undefined) {
     (store as relationalStore.RdbStore).insert('EMPLOYEE', valueBucket, relationalStore.ConflictResolution.ON_CONFLICT_REPLACE, (err, rowId) => {
       if (err) {
         console.error(`Failed to insert data. Code:${err.code},message:${err.message}`);
         return;
       }
       console.info(`Succeeded in inserting data. rowId:${rowId}`);
     })
   }

Use backup() to back up the RDB store.

   if(store != undefined) {
     (store as relationalStore.RdbStore).backup('dbBackup.db', (err) => {
       if (err) {
         console.error(`Failed to backup data. Code:${err.code},message:${err.message}`);
         return;
       }
       console.info(`Succeeded in backuping data.`);
     })
   }

Use delete() to delete data to simulate unexpected deletion or data tampering.

   let predicates = new relationalStore.RdbPredicates('EMPLOYEE');
   predicates.equalTo('NAME', 'Lisa');
   if(store != undefined) {
     (store as relationalStore.RdbStore).delete(predicates).then((rows: number) => {
       console.info(`Delete rows: ${rows}`);
     }).catch((err: BusinessError) => {
       console.error(`Failed to delete data. Code:${err.code},message:${err.message}`);
     })
   }

Use restore() to restore the RDB store.

   if(store != undefined) {
     (store as relationalStore.RdbStore).restore('dbBackup.db', (err) => {
       if (err) {
         console.error(`Failed to restore data. Code:${err.code},message:${err.message}`);
         return;
       }
       console.info(`Succeeded in restoring data.`);
     })
   }