Code Optimization, PostgreSQL BLOBs (Cheat Method)

Frank D. Engel, Jr. fde101 at fjrhome.net
Tue Oct 12 14:31:40 EDT 2004


I tried that before and for some reason it did not seem to work.  
However, at least one other app will need to access the data, and I 
seriously doubt that app will like the idea of the images being base64 
encoded, so that idea will not work anyway.

I'm thinking about maybe translating the functions into Pascal or C and 
encapsulating them into an external, if I can figure out how to do it.  
Maybe...

On Oct 12, 2004, at 2:19 PM, Jan Schenkel wrote:

> --- "Frank D. Engel, Jr." <fde101 at fjrhome.net> wrote:
>> After some research and "playing," I've *finally*
>> found a way to get
>> info into and out of PostgreSQL BYTEA BLOBs through
>> RevDB, but it is
>> painfully slow.  I wrote the following functions:
>>
>> function dbBLOB bdat
>>    put "'" into x
>>    repeat for each char c in bdat
>>      put format("\\\\%03o", charToNum(c)) after x
>>    end repeat
>>
>>    return x & "'::bytea"
>> end dbBLOB
>>
>> function dbUNBLOB adat
>>    put empty into x
>>    put 0 into y
>>    put 0 into n
>>    put false into esc
>>    repeat for each char c in adat
>>      if esc then
>>        if c is "\" then
>>          put "\" after x
>>          put false into esc
>>        else
>>          put (8 * y) + c into y
>>          add 1 to n
>>          if n is 3 then
>>            put numToChar(y) after x
>>            put 0 into y
>>            put 0 into n
>>            put false into esc
>>          end if
>>        end if
>>      else if c is "\" then put true into esc
>>      else put c after x
>>    end repeat
>>
>>    return x
>> end dbUNBLOB
>>
>>
>> dbBLOB encodes binary data stored in strings (such
>> as the text property
>> of an image) into a BYTEA literal which can be used
>> in an INSERT or
>> UPDATE statement:
>>
>> on mouseUp
>>    revExecuteSQL the database of this stack, "INSERT
>> INTO table1 VALUES
>> (" & dbBLOB(image "Image 1") & ")"
>> end mouseUp
>>
>>
>> dbUNBLOB decodes binary data returned from the
>> server back into a
>> string:
>>
>> on mouseUp
>>    put revQueryDatabase(the database of this stack,
>> "SELECT * FROM
>> table1") into q
>>    if q is an integer then
>>      if revNumberOfRecords(q) > 0 then
>>        put dbUNBLOB(revDatabaseColumnNumbered(q, 1))
>> into image "Image 1"
>>      else answer "No Records"
>>      revCloseCursor q
>>    else answer q titled "Error"
>> end mouseUp
>>
>>
>> Perhaps the functions will help someone else in a
>> similar situation;
>> also, if anyone can find a way to speed these up, I
>> would certainly
>> appreciate it...
>>
>> Frank D. Engel, Jr.
>
> Hi Frank,
>
> If no other applications needs to access the data, you
> could just store a Base64 copy of the image data in a
> field of type text.
>
> A bit late now, I know...
>
> Jan Schenkel.
>
> =====
> "As we grow older, we grow both wiser and more foolish at the same 
> time."  (La Rochefoucauld)
>
>
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-----------------------------------------------------------
Frank D. Engel, Jr.  <fde101 at fjrhome.net>

$ ln -s /usr/share/kjvbible /usr/manual
$ true | cat /usr/manual | grep "John 3:16"
John 3:16 For God so loved the world, that he gave his only begotten 
Son, that whosoever believeth in him should not perish, but have 
everlasting life.
$



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