Eclipse cleanup - what are the ".index" files - can I safely delete them?

Question

Trying to reduce the size of my (DB synced) workspace - realized that the folder

${workspace_loc}\.metadata\.plugins\org.eclipse.jdt.core

was taking ~35 Mbytes - the contents of the folder are .index files (which take the most space) and some others (which are a couple Kb worth) :

[0-9]*\.index
externalLibsTimeStamps
indexNamesMap.txt
invalidArchivesCache
javaLikeNames.txt
nonChainingJarsCache
participantsIndexNames.txt
savedIndexNames.txt
variablesAndContainers.dat

I can't seem to be able to find docs on those. Can I safely delete them ? Can you point me to some docs on the JDT plugin folders/files contained in ${workspace_location}\.metadata\ directory ?
Is there any way via the gui to clean up the caches (preferably periodically) ?

PS : I 'm on Kepler if this makes a difference PS2 : links to docs may be links to code comments and such

Answer 1

Yes, you can safely delete them, but it is not very useful.

According to an answer to How would you access Eclipse JDT index?, these files are the class index used when you "Open Type..." (in Refactor>Open Type... or via Ctrl+Shift+T). So if you delete them, next time you want to open a class using "Open Type..." the classes will be reindexed.

Therefore, deleting it for the sake of saving space has little sense, as it will be re-created. Deleting is however useful if you think you have something messed up in your index, it is a way to update it, as the refered answer suggests.