FULL rebuild deleted a document before re-ingesting it from its URI, and
the handler around that logged and continued. A 404, a timeout or any
conversion error therefore removed the document permanently.
Deleting after a successful create is not an alternative:
create_document_from_source resolves the same URI to the existing
document and updates it in place, so a trailing delete would remove the
freshly rebuilt row.
Refresh in place instead. create_document_from_source takes an internal
force flag that skips the revision and MD5 short-circuits, so an
unchanged source is still re-converted, re-chunked and re-embedded into
the existing document, and the document id survives a rebuild.
A failed refresh now falls through to the stored-content path rather
than skipping the document: FULL recreates the chunks table before the
loop, so skipping left the document present but unsearchable until the
next rebuild.
The pending-batch flush moves out of the try. A failed flush is a lost
write and should abort the rebuild, not be logged and skipped.