[dokuwiki] Re: "memory size" Error

In addition to my earlier message, I've done a little more investigating.
- tried an iterator based on array_pop() on the basis that as the input call stack is processed its memory requirements are reduced in step with the increasing memory requirements of the output call stack.
Virtually no change in memory use. Significant increase in processing time.
Tentative conclusion, PHP's shallow copy mechanism is working in DW's favour, changes in processing of call rewriters seem to do no more than achieve the same efficiencies already achieved by PHP at a cost of greater processing time. 

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Although this problem seems to apply to tables. All of the syntax modes which use call rewriters (e.g. lists, quotes, footnotes) use a similar structure to process their call stacks so are vulnerable to the same issue. Its possible the problem doesn't seem to occur with these other modes because pages aren't created with extremely large instances of their syntax, ie. big tables are more common and larger than big lists or big footnotes. The instruction set required to produce a table is more complex that the instruction set required to produce the output of the other modes. I think that is a marginal issue, the main issue is that when the handler processes a call rewriter's call stack it needs to double the memory requirements of that stack.
It looks to me that significant improvements in memory usage by the handler will be difficult to achieve without significant changes to the way it operates. 

For now, my best advice is:
- don't make really large wiki pages, especially ones with really large tables. - if you must have really large tables, try to break them up. Processing several smaller tables requires less total memory than processing a single large table. 
- increase PHP's memory_limit

A couple of things to be looked at are:
- detailed look at where/how memory is being used in parser/handler/ renderer - reducing duplication of instruction strings, say by using an index to a separate table containing the strings 

Andi has opened an item for this in the bug tracker, 
http://bugs.splitbrain.org/index.php?do=details&task_id=1357

- Chris
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