I have been having the same exact problem. Trying to have Zotero rebuild the full-text index, I keep leaving it on - often as the only program running - and then see that it shut down on its own.
@persianphilosopher: If you're still seeing this, Zotero 5.0.56, now available, should reduce memory consumption when clearing the full-text index.
(I'm not totally sure what you were trying to do, though — were you trying to clear the index, index unindexed items, or rebuild it completely. Note that there's generally no need to use these options manually, though the "Index Unindexed Items" option can be useful if you had an older version of Zotero without the PDF tools installed.)
I had "manually" checked by searching for strings I expected returned from indexed items and it was not finding them. (Used to find them in Z4) so that's why I had to rebuild it.
Upgrade Storage
Report id: 1038411909
(I'm not totally sure what you were trying to do, though — were you trying to clear the index, index unindexed items, or rebuild it completely. Note that there's generally no need to use these options manually, though the "Index Unindexed Items" option can be useful if you had an older version of Zotero without the PDF tools installed.)
I had "manually" checked by searching for strings I expected returned from indexed items and it was not finding them. (Used to find them in Z4) so that's why I had to rebuild it.