Thread

1. Explain

   Jeff Davis <jdavis@wasabimg.com> — 2001-01-05T09:18:34Z

   How can I conveniently handle output from an EXPLAIN query inside an
   application? It appears to just immediately send the output to the stdout of
   whatever program uses it. Is there a way to get the output inside a program,
   with libpq or otherwise? I would actually like to be able to get the output in
   a PHP script, but getting it in any application would be nice.
   
   Thanks,
   	Jeff Davis
    -- 
   Jeff Davis
   jdavis@dynworks.com
   http://dynworks.com
   
   

2. Re: Explain

   Heiko Irrgang <irrgang@sc-networks.de> — 2001-01-05T09:25:12Z

   >How can I conveniently handle output from an EXPLAIN query inside an
   >application? It appears to just immediately send the output to the stdout of
   >whatever program uses it. Is there a way to get the output inside a program,
   >with libpq or otherwise? I would actually like to be able to get the output in
   >a PHP script, but getting it in any application would be nice.
   
   AFAIK it dont works directly, but you can do the following:
   
   <?php
   $f=popen("psql -U username -c 'explain select * from table' -d dbname 
   2>/dev/stdout","r");
   
   while($nextline=fgets($f,4096)) {
            echo($nextline."<br>");
   }
   pclose($f);
   ?>
   
   this would dump the explain-result as you get it in psql as html-text.
   
   with popen("command","r") you open a stream to the command and 
   because psql seems to send
   the result of explain to stderr you have to redirect it to stdout 
   (2>/dev/stdout)
   
   then you can handle the filedescriptor delivered by popen() as a normal file
   with fgets(), but you have to close it with pclose() not fclose().
   
   this works exactly the same within a c program but i dont know much
   about programming postgres in c. it may be possible to have the
   same result directly with libpq, but for php this seems to be
   the only way to do this.
   
   -- 
   SC-Networks                             www: www.SC-Networks.de
   Web Design, Netzwerke,
   3D Animation und Multimedia
   Heiko Irrgang                           Tel.: 08856/9392-00
   Im Thal 2                               Fax:  08856/9392-01
   
   82377 Penzberg                          Mail: Irrgang@SC-Networks.de
   
   

3. Re: Explain

   Tom Lane <tgl@sss.pgh.pa.us> — 2001-01-05T16:43:24Z

   Jeff Davis <jdavis@wasabimg.com> writes:
   > How can I conveniently handle output from an EXPLAIN query inside an
   > application? It appears to just immediately send the output to the stdout of
   > whatever program uses it. Is there a way to get the output inside a program,
   > with libpq or otherwise?
   
   The EXPLAIN result is sent as a NOTICE message, so you can trap it by
   setting libpq's notice processor function --- see PQsetNoticeProcessor.
   
   			regards, tom lane