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.