RE: JVM in the database

From: Noveljic Nenad <nenad.noveljic_at_vontobel.com>
Date: Thu, 12 Dec 2019 14:08:25 +0000
Message-ID: <6126_1576159718_5DF249E6_6126_1626_1_5b2627ffac444c9595af0171bd03c570_at_vontobel.com>



The buffer size in Jeff’s code is the blob size length (blob.length), capped with 2*10^7 .

In contrast, your example uses blob.getBufferSize.

It wasn’t until now that I noticed the difference - thanks.

Further, getBufferSize seems to be capped to 32k for large blob variables. However, I suspect there might be some boundary cases where the capping doesn’t work correctly.

I’m not aware of any generic tracing capabilities in the database JVM, which is relevant when dealing with poorly instrumented and supported applications. In conventional JVMs one could use Java debugger or log4j. Falling back to tracing Oracle C functions is usually time consuming, especially with just-in-time compiled code. The lack of instrumentation is a major argument against the database JVM, in my opinion.

Best regards,

Nenad

https://nenadnoveljic.com/blog/

From: Tim Hall <tim_at_oracle-base.com> Sent: Dienstag, 10. Dezember 2019 15:27 To: Noveljic Nenad <nenad.noveljic_at_vontobel.com> Cc: Jeff Chirco <backseatdba_at_gmail.com>; ORACLE-L (oracle-l_at_freelists.org) <oracle-l_at_freelists.org> Subject: Re: JVM in the database

Having said that, maybe I'm not guilty. My example uses,

int size = myBlob.getBufferSize();

According to the docs, this does the following.

getBufferSize(): Returns the ideal buffer size, according to calculations by the JDBC driver, to use in reading and writing BLOB data. This value is a multiple of the chunk size (see getChunkSize() below) and is close to 32K.

I'll consider myself off the hook. :)

Cheers

Tim...

On Tue, Dec 10, 2019 at 2:18 PM Tim Hall <tim_at_oracle-base.com<mailto:tim_at_oracle-base.com>> wrote: Hi.

That looks strangely familiar.

https://oracle-base.com/articles/8i/export-blob

At it seems it's my fault your vendor didn't have a limit, because they probably copied me and I don't. :)

From 9i onward you could do it with UTL_FILE instead of a Java stored procedure..

https://oracle-base.com/articles/9i/export-blob-9i

Cheers

Tim...

On Mon, Dec 9, 2019 at 11:08 PM Noveljic Nenad <nenad.noveljic_at_vontobel.com<mailto:nenad.noveljic_at_vontobel.com>> wrote: You‘ve done it correctly by limiting the buffer size for larger blobs. But our vendor, unfortunately, didn‘t, so we‘re getting OutOfMemoryError for the blobs larger than ~512M. Curiously, this error can‘t be fixed by just configuring more memory, as it’s a consequence of some undocumented hard-coded limits specific to the database JVM:  https://nenadnoveljic.com/blog/troubleshooting-java-lang-outofmemoryerror-in-the-oracle-database/

Thanks,
Nenad

Von: Jeff Chirco <backseatdba_at_gmail.com<mailto:backseatdba_at_gmail.com>> Datum Montag, 09. Dez. 2019, 9:43 PM
An: Noveljic Nenad <nenad.noveljic_at_vontobel.com<mailto:nenad.noveljic_at_vontobel.com>> Cc: ORACLE-L (oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>) <oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>> Betreff: Re: JVM in the database

Here you go. I found this on the internet years ago so I take no credit no do I understand much about it. But it works great.

create or replace and compile java source named blobhandler as import java.lang.*;

    import java.sql.*;
    import oracle.sql.*;
    import java.io.*;
    public class BlobHandler {

      public static void ExportBlob(String myFile, BLOB myBlob) throws Exception {
        File binaryFile = new File(myFile);
        FileOutputStream outStream = new FileOutputStream(binaryFile);
       InputStream inStream = myBlob.getBinaryStream();
       int size;
       if (myBlob.length()> 20000000) {  // tune this to whatever appropriate value
         size = 20000000;
       } else {
         size = (int)myBlob.length();
       }
       byte[] buffer = new byte[size];
       int length = -1;
       while ((length = inStream.read(buffer)) != -1)
       {
         outStream.write(buffer, 0, length);
         outStream.flush();
       }
       inStream.close();
       outStream.close();
     }

   }

CREATE OR REPLACE PROCEDURE ExportBlobJava (p_file IN VARCHAR2,

                                                                                 p_blob   IN BLOB)
    AS
       LANGUAGE JAVA
       NAME 'BlobHandler.ExportBlob(java.lang.String, oracle.sql.BLOB)';



On Fri, Dec 6, 2019 at 7:21 AM Noveljic Nenad <nenad.noveljic_at_vontobel.com<mailto:nenad.noveljic_at_vontobel.com>> wrote: Hi Jeff,

Have you ever processed files larger than 536870895 bytes?

Could you share the snippet which writes the BLOB into a file? Do you possibly stream it to an InputStream object, buffer it, and then stream it to the file with the FileOutputStream object?

If yes, what’s the buffer size? The code to allocate the buffer should look similar to this:

byte[] buffer = new byte[bufferSize];

Best regards,

Nenad

https://nenadnoveljic.com/blog/

I use a java procedure to dump blob files to an actual file. We store some PDF's in the database as blob and at times they need to be dumped to a files. Usually its when they want hundreds at time. We found doing this in a loop with PL/SQL was really slow and slower over time. I found a Java procedure to do this and is is super quick. We also have another to get file and directory information. It returned back more information that PL/SQL and also was really fast.



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Received on Thu Dec 12 2019 - 15:08:25 CET

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