Reply to Re: Solution (was: Re: Reading Database BLOB with showing progress information)

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Posted by Gary L. Burnore on 09/28/05 14:33

On 28 Sep 2005 04:21:07 -0700, "ssp" <ssp@planicsware.de> wrote:

>Dear all,
>
>finally I found a solution (or better our sysadmin told me to read
>mysql manual user comments in detail;):
>
>the trick is: mysql trades BLOBs as kind of huge strings. so one can
>use LENGTH on a column to get its content-length and then read out
>using SUBSTRING sequentially.
>
>snippet (assuming that $__DB = PEAR:DB Connection is correctly
>initiated) :
><?
>$stQuery = "SELECT LENGTH(PIF_FILE_BLOB) FROM PIF WHERE PIF_ID=2";
>$iFileSize = $__DB->getOne($stQuery);
>
>$i=0;
>$iPos = 1; //Startposition
>$iLength = 4096; //Readbuffer size
>$iTotal = ($iFileSize/$iLength); //how many queries ?
>$iStatus = ceil($iTotal/20); //after 20 queries print out a char
>
>//open Output File Handle
>printf("Lade neu.exe [%d kB] [",ceil($iFileSize/1024));
>$oFileHandle = fopen('.dev/neu.exe','w');
>
>while (!isset($stRead) || $stRead!='') {
> $i++;
> $stQuery = sprintf("SELECT substring(PIF_FILE_BLOB,%d,%d) FROM PIF
>WHERE PIF_ID=2",$iPos,$iLength);
> $iPos+=$iLength;
> $stRead = $__DB->getOne($stQuery);
> fwrite($oFileHandle,$stRead);
> if ($i%$iStatus==0) echo "=";
>}
>echo "]";
>
>fclose($oFileHandle);
>
>?>
>
>
>This works very good for me

I've seen this sort of thing before. Adding some time to the actual
process to show progress makes the user believe it's going "faster"
than if they see nothing happening.
--
gburnore@databasix dot com
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