快速读取使用simpleQueryForBlobFileDescriptor内SQLite的斑点？

本文介绍了快速读取使用simpleQueryForBlobFileDescriptor内SQLite的斑点？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我用下面的code读斑点与SQLite的在我的Andr​​oid应用100KB和1000KB的大小：

公共对象getCachefromDb（字符串sIdentifier）{    字符串sSQL ='+ sIdentifier +选择从cachtable其中identifier =缓存';    光标C = NULL;    尝试{        C = connection_chronica.rawQuery（sSQL，NULL）;    }赶上（SQLiteException E）{        Log.v（SQLite的EXCETION，e.getMessage（））;    }    c.moveToFirst（）;    Log.v（DEBUG负荷高速缓存，sIdentifier：+ sIdentifier）;    字节[] BDATA = NULL;    尝试{        BDATA = c.getBlob（0）;    }赶上（例外五）{        e.printStackTrace（）;    }    对象o = NULL;    如果（BDATA！= NULL）{        ByteArrayInputStream的BOS =新ByteArrayInputStream进行（BDATA）;        ObjectInputStream的OIS;        尝试{            OIS =新的ObjectInputStream（BOS）;            O = ois.readObject（）;        }赶上（StreamCorruptedException E）{            // TODO自动生成catch块            e.printStackTrace（）;        }赶上（IOException异常五）{            // TODO自动生成catch块            e.printStackTrace（）;        }赶上（ClassNotFoundException的E）{            // TODO自动生成catch块            e.printStackTrace（）;        }    }    c.close（）;    返回O;}

我想优化读取速度，我发现文章mentoining simpleQueryForBlobFileDescriptor。

我的问题：这是否帮助我阅读BLOBS更快？如果是的话我如何使用它？

从其他职位举例：

SQLiteStatement GET = mDbpileStatement（    选择blobColumn+    FROM tableName值+    WHE​​RE _id = 1+    LIMIT 1）;ParcelFileDescriptor结果= get.simpleQueryForBlobFileDescriptor（）;FIS的FileInputStream =新的FileInputStream（result.getFileDescriptor（））; //读到像任何其他

解决方案

我的测试结果说，它的速度较慢。

长期测试后，我发现，在使用simpleQueryForBlobFileDescriptor较慢。见下code。我的老code例如读取390毫秒一个blob和新的code。与simpleQueryForBlobFileDescriptor读取805毫秒同一斑点。我读的地方，simpleQueryForBlobFileDescriptor应该是一滴读数非常快，但这似乎不是在我的测试。 Perhabs我不这样做是否正确？ （ 我希望如此 ）。任何其他提示。

公共对象getCachefromDb_old（字符串sIdentifier）{    Log.v（DEBUG LOAD BLOB，开始：+ sIdentifier）;    对象o = NULL;    尝试{        // Erstelle EIN SQLStatemant麻省理工学院einer InClause        字符串sSQL ='+ sIdentifier +选择从cache表，其中标识=缓存';        SQLiteStatement GET = connection_chronicapileStatement（sSQL）;        ParcelFileDescriptor结果= get.simpleQueryForBlobFileDescriptor（）;        FIS的FileInputStream =新的FileInputStream（result.getFileDescriptor（））;        ObjectInputStream的inStream中=新的ObjectInputStream（FIS）;        O = inStream.readObject（）;    }赶上（StreamCorruptedException E1）{        // TODO自动生成catch块        e1.printStackTrace（）;    }赶上（IOException异常E1）{        // TODO自动生成catch块        e1.printStackTrace（）;    }赶上（ClassNotFoundException的E）{        // TODO自动生成catch块        e.printStackTrace（）;    }    Log.v（DEBUG LOAD BLOB，结束：+ sIdentifier）;    返回O;}

I am reading blobs with size between 100kb and 1000kb from SQlite in my Android App using the following code :

public Object getCachefromDb(String sIdentifier){ String sSQL = " Select cache from cachtable where identifier='" + sIdentifier + "'"; Cursor c = null; try { c = connection_chronica.rawQuery(sSQL, null); } catch (SQLiteException e) { Log.v("SQLite Excetion", e.getMessage()); } c.moveToFirst(); Log.v("DEBUG load Cache","sIdentifier : " + sIdentifier); byte[] bData=null; try{ bData = c.getBlob(0); }catch(Exception e){ e.printStackTrace(); } Object o = null; if (bData!=null){ ByteArrayInputStream bos = new ByteArrayInputStream(bData); ObjectInputStream ois; try { ois = new ObjectInputStream(bos); o=ois.readObject(); } catch (StreamCorruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } } c.close(); return o; }

I would like to optimize the speed of reading and I found articles mentoining simpleQueryForBlobFileDescriptor.

My question : Does this help me reading BLOBS faster ? and if so how can I use it ?

Example from other posts:

SQLiteStatement get = mDbpileStatement( "SELECT blobColumn" + " FROM tableName" + " WHERE _id = 1" + " LIMIT 1" ); ParcelFileDescriptor result = get.simpleQueryForBlobFileDescriptor(); FileInputStream fis = new FileInputStream(result.getFileDescriptor()); // read like any other

解决方案

My Tests results says its slower.

After long testing I found out, that using simpleQueryForBlobFileDescriptor is slower. See following code. My old code for example reads a blob in 390 miliseconds and the new code with simpleQueryForBlobFileDescriptor reads the same blob in 805 ms. I read somewhere that simpleQueryForBlobFileDescriptor should be very fast for blob readings, but this seems not to be in my tests. Perhabs I am not doing it properly ? ( I hope so ). Any other hints.

public Object getCachefromDb_old(String sIdentifier){ Log.v("DEBUG LOAD BLOB","Start : " + sIdentifier); Object o = null; try { // Erstelle ein SQLStatemant mit einer InClause String sSQL = " Select cache from cachetable where identifier='" + sIdentifier + "'"; SQLiteStatement get = connection_chronicapileStatement(sSQL); ParcelFileDescriptor result = get.simpleQueryForBlobFileDescriptor(); FileInputStream fis = new FileInputStream(result.getFileDescriptor()); ObjectInputStream inStream = new ObjectInputStream(fis); o=inStream.readObject(); } catch (StreamCorruptedException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } catch (IOException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } Log.v("DEBUG LOAD BLOB","End : " + sIdentifier); return o; }