oracle 下操作blob字段是否会产生大量redo

操作blob字段是否会产生大量redo,答案是不会。以下来做一个实验,測试数据库版本号是11.2.0.1.0:

--创建一张表做測试之用

create table test_blob

(

  id number,

  tupian blob

);

import java.io.FileInputStream;
import java.io.OutputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import oracle.sql.BLOB;

public class BlobExample {
    static final String driver_class  = "oracle.jdbc.driver.OracleDriver";
    static final String connectionURL = "jdbc:oracle:thin:@10.10.15.25:1521:orcl";
    static final String userID        = "test";
    static final String userPassword  = "test";

    private void insertTestBlob() {
        Connection conn=null;
        Statement stm=null;
        ResultSet rs=null;
        BLOB blob = null;
        FileInputStream fin=null;
        OutputStream out=null;
        try{
            conn = DriverManager.getConnection(connectionURL, userID, userPassword);
            stm = conn.createStatement();
            conn.setAutoCommit(false);
            String sql = "insert into test_blob values(1,EMPTY_BLOB())";
            stm.executeUpdate(sql);
            rs = stm.executeQuery("SELECT tupian FROM test_blob WHERE id=1 FOR UPDATE ");
           fin = new FileInputStream("d://20130317.jpg");
           byte[] blobBuf = new byte[(int)fin.available()];
           fin.read(blobBuf);
           fin.close();

           if(rs.next()) {
            blob = (oracle.sql.BLOB)rs.getBlob(1);
            out = blob.getBinaryOutputStream();
            out.write(blobBuf);
            out.close();
            conn.commit();
           }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            try {
                rs.close();
                stm.close();
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    public static void main(String args[]){
        BlobExample  blobClobExample = new BlobExample();
        blobClobExample.insertTestBlob();
    }
}

--做非常多次

insert into test_blob  select * from test_blob;

insert into test_blob  select * from test_blob;

insert into test_blob  select * from test_blob;

.......

commit;

--准备dump block

select rowid,

       dbms_rowid.rowid_object(rowid) object_id,

       dbms_rowid.rowid_relative_fno(rowid) file_id,

       dbms_rowid.rowid_block_number(rowid) block_id,

       dbms_rowid.rowid_row_number(rowid) num

  from test_blob;

--update之前blob的状态

alter session set tracefile_identifier = 'Look_For_Me';

alter system switch logfile;

alter system switch logfile;

alter system dump datafile 5 block 3274932;

--update之后blob的状态。同一时候測试一下。此时update产生了多少redo

select name, value

  from v$mystat, v$statname

 where v$mystat.statistic# = v$statname.statistic#

   and v$statname.name = 'redo size'

update test_blob set tupian = null;

commit;

select name, value

  from v$mystat, v$statname

 where v$mystat.statistic# = v$statname.statistic#

   and v$statname.name = 'redo size'

alter system switch logfile;

alter system switch logfile;

alter session set tracefile_identifier = 'Look_For_Me1';

alter system dump datafile 5 block 3274932;

測试结果：我传的图片是5.1M，一共产生了350条数据，都把blob置为空以后，共产生了7.6M的redo，非常显然是blob的内容是没有产生redo的。

分析原理，得借助分析dump block的内容,能够看到设置blob字段为null后产生的redo仅仅是类似col  1: [84]这些信息。

blob设置为空曾经:

Block header dump:  0x0171f8b4

 Object id on Block? Y

 seg/obj: 0x17f1d  csc: 0x9a8.7256c728  itc: 2  flg: E  typ: 1 - DATA

     brn: 0  bdba: 0x171f8b0 ver: 0x01 opc: 0

     inc: 0  exflg: 0

 

 Itl           Xid                  Uba         Flag  Lck        Scn/Fsc

0x01   0x0003.01b.000033cf  0x00c001f5.132c.39  --U-    1  fsc 0x0000.7256c775

0x02   0x0000.000.00000000  0x00000000.0000.00  ----    0  fsc 0x0000.00000000

bdba: 0x0171f8b4

data_block_dump,data header at 0x2b35c4c56064

===============

tsiz: 0x1f98

hsiz: 0x14

pbl: 0x2b35c4c56064

     76543210

flag=--------

ntab=1

nrow=1

frre=-1

fsbo=0x14

fseo=0x1f12

avsp=0x1f29

tosp=0x1f29

0xe:pti[0] nrow=1
offs=0

0x12:pri[0] offs=0x1f12

block_row_dump:

tab 0, row 0, @0x1f12

tl: 91 fb: --H-FL-- lb: 0x1  cc: 2

col  0: [ 2]  c1 02

col  1: [84]

 00 54 00 01 01 0c 00 00 00 01 00 00 00 01 00 00 00 0e 48 41 00 40 05 00 00

 00 02 76 12 a0 00 00 00 00 00 02 01 71 f8 bc 01 71 f8 bd 01 71 f8 be 01 71

 f8 bf 01 71 f8 bb 01 ca 11 3d 01 ca 11 3e 01 ca 11 3f 01 ca 11 39 01 ca 11

 3a 01 ca 11 3b 01 ca 11 3c

LOB

Locator:

  Length:        84(84)

  Version:        1

  Byte Length:    1

  LobID: 00.00.00.01.00.00.00.0e.48.41

  Flags[ 0x01 0x0c 0x00 0x00 ]:

    Type: BLOB 

    Storage: BasicFile

    Enable Storage in Row 

    Characterset Format: IMPLICIT

    Partitioned Table: No

    Options: ReadWrite 

  Inode: 

    Size:     64

    Flag:     0x05 [ Valid InodeInRow(ESIR) ]

    Future:   0x00 (should be '0x00')

    Blocks:   630

    Bytes:    4768

    Version:  00000.0000000002

    DBA Array[12]:

      0x0171f8bc 0x0171f8bd 0x0171f8be 0x0171f8bf

      0x0171f8bb 0x01ca113d 0x01ca113e 0x01ca113f

      0x01ca1139 0x01ca113a 0x01ca113b 0x01ca113c

............................................................

............................................................

End dump data blocks tsn: 6 file#: 5 minblk 3274932 maxblk 3274932

blob设置为空之后:

Block header dump:  0x0171f8b4

 Object id on Block? Y

 seg/obj: 0x17f1d  csc: 0x9a8.7256c99f  itc: 2  flg: E  typ: 1 - DATA

     brn: 0  bdba: 0x171f8b0 ver: 0x01 opc: 0

     inc: 0  exflg: 0

 

 Itl           Xid                  Uba         Flag  Lck        Scn/Fsc

0x01   0x0003.01b.000033cf  0x00c001f5.132c.39  C---    0  scn 0x09a8.7256c775

0x02   0x0001.003.0000315e  0x00c0218e.1348.3a  --U-    1  fsc 0x0052.7256c9a7

bdba: 0x0171f8b4

data_block_dump,data header at 0x2b7ad6cce464

===============

tsiz: 0x1f98

hsiz: 0x14

pbl: 0x2b7ad6cce464

     76543210

flag=--------

ntab=1

nrow=1

frre=-1

fsbo=0x14

fseo=0x1f0c

avsp=0x1f29

tosp=0x1f7b

0xe:pti[0] nrow=1
offs=0

0x12:pri[0] offs=0x1f0c

block_row_dump:

tab 0, row 0, @0x1f0c

tl: 6 fb: --H-FL-- lb: 0x2  cc: 1

col  0: [ 2]  c1 02

............................................................

............................................................

End dump data blocks tsn: 6 file#: 5 minblk 3274932 maxblk 3274932