[reportlab-users] Patch to platypus/tables.py

[Tomasz Świderski]

hello,

I would like to apply patch to platypus/tables.py. Current code (2.4) is
very slow with long tables. My table is about 480 pages long so there is
a lot of splits during PDF generation. During each split 2 new Table
instances are created: one with enough data to fit into current frame,
second with rest of the data. It's OK with short tables, but in my case
PDF generation take about 720seconds on my laptop. So I checked the code
of tables.py and found a lot of unnecessary code in Table __init__
method.


1) Each time new Table instance is created, data passed to __init__ is
normalized (converted to plain string). It's makes sense when user is
creating new Table, but during the table split it's unnecessary since
new Tables are created using old Table data (which is already
normalized). To fix this, I added new attribute to __init__ method
called normalizedData. It defaults to False which means that data is not
already normalized. If normalizedData is True (during the split) data
conversion is skipped. This simple change gave me 12% performance boost.

2) Secondly during Table creation __init__ method created CellStyle
object for each cell. It's unnecessary during split since new Tables use
old Table's CellStyles. So I added cellStyles attribute to __init__ in
order to reuse old Table's cell styles during split. After this change
my PDF generation time dropped from 720s to 100s. 700% performance
boost :D


Of course performance gain strongly depends on number of cells and
splits. In my case I have 9cols * 38rows * 480pages = 164160 cells. On
each split all this data had to be normalized and CellStyle object
created for each cell (number of cells decreases with each split). With
very small Tables there will be no performance gains at all (low numer
of cells and splits).


I'm attaching my PDF and changes in diff format. Should be easy to apply
them with patch command.


Let me know if you like this patch and will include it in next reportlab
release :)


Best regards,
Tomasz Świderski
contact at tomaszswiderski.com

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