I need to move a heavy quantity of items between two collections. I tried to change direct at database the tables "item" and "collection2item", columns "owning_collection" and "item_id" respectively. Then I restarted tomcat, cleaned the cocoon cache, rebuilt the index and it's still not working.
Is the process metadata-export/metadata-import safer or easier than the above for mass move of items?
What else can I do?
Your process should be ok if you run the reindex with the -bf flags (just -f may be enough too).
Without the -f flag, the reindex (link goes to code as of DSpace 5.x) will check the last_modified value (in the item table) and only reindex items whose value in that column has changed since the last reindex. This also means that a reindex without -f should work if you also updated the last_modified timestamp.
Still not working?
If the reindex still doesn't happen, something else must be going wrong. Check your dspace.log -- are there any entries that look like "wrote item xyz to index"? If not then the items aren't being reindexed. Are there any error messages in the dspace.log around the time you do the reindex? Any error messages in the solr log file?
Also, make sure you always run the reindex (and all other dspace commands) as the same user that tomcat is running under, to avoid permissions problems. If you've ever run the commands as a different user, change the permissions of the solr data directory (probably [dspace]/solr/search/data) so that the tomcat user can create/write/delete files in it.
Overall recommendation
In most cases I'd go with batch metadata editing myself for moving items between collections, it avoids all these problems and will trigger a re-index of the affected items automatically.
The metadata import process is very reliable. It also provides a preview option that will allow you to see the changes before they are applied. After the items are updated, the proper re-indexing processes will run.
You only need to provide the item ids and the data fields you wish to edit.
If you prefer to build your CSV file by hand or from a SQL query, that will work as well. The name of the column at the top of your CSV will determine the fields to be updated.
https://wiki.duraspace.org/display/DSDOC5x/Batch+Metadata+Editing#BatchMetadataEditing-CSVFormat
