how will typoscript be executed performance wise

I'm just wandering in general how typoscript is executed performance wise.

For instance if you have the following code, how will it be executed?

if the <div id=footer"> exists put temp.footer content in it. What means that the relevant queries are only executed it the div footer exists.

or

put content temp.footer into <div id=footer"> if the div exists. What means that if the div footer doesn't exists the queries are still executed.

# Main TEMPLATE cObject for the BODY
temp.mainTemplate = TEMPLATE
temp.mainTemplate {
  
  # Feeding the content from the Auto-parser to the TEMPLATE cObject:
  template =< plugin.tx_automaketemplate_pi1
  
  # Select only the content between the <body>-tags
  workOnSubpart = DOCUMENT_BODY

  subparts {
    
    	footer < temp.footer
    	container < styles.content.get
  }
}