IBX and BLOB update
lazarus / 16-Databases

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sydenis · 2021-06-30 17:51

Ubuntu 20.04 + Lazarus 2.0.12
I use the IBSQL component from ibx4lazarus2. 4-0 to access the
Firebird 3 database
I need to write and read a BLOB field from my database.

There are no problems with reading from db:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
IBSQL1.FieldByName('blob').AsBlob.SaveToFile(MyFile);I get the desired
file.

But writing to db does not work:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
IBSQL1.ParamByName('blob').AsBlob.LoadFromFile(MyFile);error -
External: SIGSEGV

What is the problem?
Looking the error it seem that ParamByName ('blob') does not exist?
How to do it correctly?

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devEric69 · 2021-07-01 07:48

On one line you used FieldByName to save, but on the other line you
wrote ParamByName to load: is this normal?

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sydenis · 2021-07-01 12:20

I guess yes. Here is code sample:
read from db:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   with
IBSLQ1 do  begin    SQL.Text:='select blob_field from tab1 where
id=1;';    Transaction.StartTransaction;    ExecQuery;   
FieldByName('blob_field').AsBlob.SaveToFile('image.bin');   
.....write to db:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   with
IBSQL1 do  begin    SQL.Text:='update tab1 set blob_field=:blob_field
where id=1;';    Transaction.StartTransaction;   
ParamByName('blob_field').AsBlob.LoadFromFile('image.bin');   
ExecQuery;     .....What is wrong?

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tonyw · 2021-07-03 09:28

Quote from: sydenis on June 30, 2021, 07:51:39 pmUbuntu 20.04 +
Lazarus 2.0.12
I use the IBSQL component from ibx4lazarus2. 4-0 to access the
Firebird 3 database
I need to write and read a BLOB field from my database.

There are no problems with reading from db:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
IBSQL1.FieldByName('blob').AsBlob.SaveToFile(MyFile);I get the desired
file.

But writing to db does not work:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
IBSQL1.ParamByName('blob').AsBlob.LoadFromFile(MyFile);The problem is
that you are using TIBSQL in the way that you would use TIBDataset.
However, TIBSQL is working directly with the underlying Firebird
interface and that requires a different approach.

The call to ParamByName('blob').AsBlob returns the interface IBlob.
The input parameter has not yet been set and so this always returns
nil - hence the exception.

To set the value of the blob, you have to create a TIBBlobstream, load
it from a file and assign the IBlob interface returned by
TIBBlobStream to the param e.g.

var b:TIBBlobStream;
begin
  b := TIBBlobStream.create;
 try
   b.Database := IBSQL.Database;
  b.Mode := bmWrite;
    b.LoadFromFile(...);
    IBSQL.ParamByName('blob').asBlob := b.blob;
  finally
    b.free;
  end;

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sydenis · 2021-07-05 13:03

Tony, thank you very much! I used your advice and everything works
fine.
My self I found a solution through asQuad:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  
 b.LoadFromFile(...);   b.Finalize; 
 IBSQL1.ParamByName('blob').AsQuad  := b.BlobID;
thank you again

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tonyw · 2021-07-05 13:49

Quote from: sydenis on July 05, 2021, 03:03:41 pmTony, thank you very
much! I used your advice and everything works fine.
My self I found a solution through asQuad:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  
 b.LoadFromFile(...);   b.Finalize; 
 IBSQL1.ParamByName('blob').AsQuad  := b.BlobID;
thank you again
Yes - that is an equivalent statement.