[reportlab-users] Reportlab performance

[Andy Robinson]

On 12 May 2010 14:20, Leszek Syroka <leszek.marek.syroka at cern.ch> wrote:

> Hello,

>

> Right now our main concern is performance of 'platypus'. Creating a

> document, similar to attached one, but containing 1032 pages, about 1 200

> 000 characters and no images takes about 12 minutes. Is it a normal time of

> creating such document?


No, this is not normal.   We construct the entire document in memory,
but yours is simple text.

I emailed separately about the possibility of some commercial support
but whichever way you want to do it, it would be useful is you could
post some code here to show how you build up the Platypus document.

Are you using a big table which spans many pages?  This could cause
problems and, looking at your document, it should not be necessary.



> Moreover I found out that to insert the table of contents document is

> created in three iterations. First time to create a document with blank

> table of contents, second one to put there and adjust dynamically created

> one and third time to fit the table of contents containing more than one

> page. Is it possible to make this operation only once?


The TableOfContents widget in Platypus does it 2x, or 3x as you say.
If you can inspect your content 'up front' and work out how many
sections there are and their titles, there will probably be a way to
'preload' the table of contents with this to eliminate at least one
pass.

There is also another technique we use in our commercial package using
delayed 'Form XObjects'.   We inspect the content up-front and make a
table containing all the entries, which goes into the story.  In the
right column we insert a 'Form XObject reference' (canvas.doForm(...))
saying 'draw the form "chapterXX" here', even though it isn't defined
yet.  Then, on the way through the document, the forms get defined.
So single passes are possible.    However, we have not packaged this
up to make it easy to use in the open source package


> I would also like to know how much quicker is using pdfgen library in favor

> of platypus, which for our application is a bit to slow.



If you need to 'move down the page' and draw paragraphs, you will need
Platypus, or something like it.   However we have to eliminate any
backtracking, memory wastage and multiple passes first.


Best Regards,


-- 
Andy Robinson
CEO/Chief Architect
ReportLab Europe Ltd.
Media House, 3 Palmerston Road, Wimbledon, London SW19 1PG, UK
Tel +44-20-8545-1570