Reading OracleBlob throws exception when InitialLOBFetchSize is > 0

User_5RTMF

Hello,

using ODP.NET, I'm having issue when reading blob field as stream (using GetOracleBlob),

I don't know where to report a bug, so putting it here.

i'm using Oracle.ManagedDataAccess Nuget package version 19.10.0 (latest)

1. Have InitialFetchLOBSize is > 0

2. get blob stream with 'GetOracleBlob'

3. read first N bytes, but less than InitialFetchLOBSize

4. then read next portion of bytes, which would go over InitialFetchLOBSize cached bytes.

 

Result:

it throws exception

"Source array was not long enough. Check srcIndex and length, and the array's lower bounds."

  at System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable)

  at System.Array.Copy(Array sourceArray, Int64 sourceIndex, Array destinationArray, Int64 destinationIndex, Int64 length)

  at OracleInternal.ServiceObjects.OracleBlobImpl.Read(Int64 locatorOffset, Int64 numBytesToRead, Int64 outBufferOffset, Byte[]& outBuffer)

  at Oracle.ManagedDataAccess.Types.OracleBlob.Read(Byte[] buffer, Int32 offset, Int32 count)

To give example with specific numbers:

- InitialFetchLOBSize=32,

- read first 16 bytes (or any number under 32, or you can just set Position to 16, or 31, doesn't matter)

- read next 32 bytes (so requested data chunk will read some of already cached data and some new)

sample code:

command.CommandText = @"select BLOB from table";

command.InitialLOBFetchSize = 32;

var reader = command.ExecuteReader()) {

while (reader.Read()) {

  if (reader.IsDBNull(0)) continue;

  using (var blob = reader.GetOracleBlob(0)) {

    blob.Position = 16;

    // this will throw exception

    blob.Read(buffer, 0, 64);

  }

}

Alex Keh-Oracle

I was able to reproduce the problem once I added a second row of LOB values. I filed bug 32190103 to track the issue.

User_5RTMF

I've just discovered there's same issue when InitialLOBFetchSize=-1 (get whole blob),

and you read past 32KB

(so read first 4KB, and then try reading next 32KB in one chunk)

Alex Keh-Oracle

I am able to execute your code successfully against a 19c DB. Is the problem the buffer byte array that is not large enough?

User_5RTMF

https://community.oracle.com/tech/developers/discussion/comment/16776091#Comment_16776091

buffer is large enough, 1MB

testing against "Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production",

but i was pretty sure it's client problem

Alex Keh-Oracle

I was able to reproduce the problem once I added a second row of LOB values. I filed bug 32190103 to track the issue.

User_5RTMF

https://community.oracle.com/tech/developers/discussion/comment/16776238#Comment_16776238

where can I check for a bug status, to be up to date?

Alex Keh-Oracle

If you or a member of your team have an Oracle Support account, you can log into https://support.oracle.com/

From there, you can search on the bug number to get its status.

Alex Keh-Oracle

We've identified the root cause and will have a fix for this bug. The planned patch is set for the October Release Update. As a temporary workaround, please set the OracleBlob.Position as 0 or use OracleBlob.Value instead.