657: Cut-down the Tempcode preprocessing step - Composr CMS feature tracker

ID	Project	Category	View Status	Date Submitted	Last Update

657	Composr	core	public	2012-07-02 18:28	2013-09-29 22:50

Reporter	Chris Graham	Assigned To	Chris Graham
Priority	normal	Severity	feature
Status	resolved	Resolution	fixed

Summary	657: Cut-down the Tempcode preprocessing step
Description	The preprocessor runs on the Tempcode tree of the known output before actually output and handles the following symbols: - PAGE_LINK (reason: so that we only need a single query to find all the moniker URLs for particular IDs being linked to -- the preprocessor gathers a list to lookup) - SET (reason: GET/SET is not linear, we need something SET in a future template to GET into an earlier one) - JAVASCRIPT_INCLUDE/CSS_INHERIT/CSS_INCLUDE (reason: dependencies must be handled via <head>, i.e. before body output) - BLOCK/LOAD_PANEL/LOAD_PAGE (reason: the block/panel/page may require some Javascript/CSS to be loaded into <head>) - FACILITATE_AJAX_BLOCK_CALL/FRACTIONAL_EDITABLE (reason: these have Javascript/CSS dependencies to be loaded into <head>) - TRIM/JS_TEMPCODE/CSS_TEMPCODE (reason: these all may couch heavy resource loading, so we look deep into them if the template-tree is being viewed so that an accurate tree may be rendered) An optimisation means that preprocessing is not too costly due to removing the need for it to work via a tree traversal, but the optimisation itself introduces an inefficiency - preprocess-requirement notes need to be passed around during attach and bind operations, which uses some memory (not as bad as it looks due to how PHP handles references) and extra loop CPU time. We want to minimise the preprocessable symbol list. PAGE_LINK is already optimised out in 656 We can get rid of most of SET if we change the semantics. Make it so that they always run linear, and introduce a new SET__NON_LINEAR that is used much more rarely (in fact, ban its use in all default templates). For JAVASCRIPT_INCLUDE/CSS_INHERIT/CSS_INCLUDE/BLOCK/LOAD_PANEL/LOAD_PAGE/FACILITATE_AJAX_BLOCK_CALL/FRACTIONAL_EDITABLE removal we can just inline the CSS/Javascript in <body>, but have our self-learning cache (653) learn of its late-inclusion so that on refresh it will be put in <head> properly. This is technically invalid HTML (for the CSS case), however it is only invalid for a performance reason (slow rendering) and we're doing this for performance. Make control this via an option. For TRIM/JS_TEMPCODE/CSS_TEMPCODE we can just make the Template tree smarter. RESULT: By default nothing needs preprocessing. Add a config option to enable preprocessing, off-by-default. This will allow further optimisation for output streaming (in separate task).
Additional Information	Summary: - Change SET semantics - Add SET__NON_LINEAR - Ensure SET__NON_LINEAR is not required in any default templates - Eliminate preprocessing of CSS/JS requiring ones, if an option is set -- allowing invalid HTML on first-load and having the self-learning cache fix it for next load - Make template tree smarter - Add config option to enable preprocessing
Tags	Type: Performance
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Time estimation (hours)	9
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