If anyone, after upgrading to MW 1.34, is finding out that any recently edited pages disappear completely from the index, fear not. There's a fix.
MediaWiki is changing the manner in which content is referenced in the database. To configure Sphinx to correctly index all pages using the new schema, change the following sphinx.conf parameter:
sql_query = SELECT page_id, page_title, page_namespace, page_is_redirect, old_id, old_text FROM page, revision, text WHERE rev_id=page_latest AND old_id=rev_text_id
to:
sql_query = SELECT page_id, page_title, page_namespace, page_is_redirect, old_id, old_text FROM page, slots, content, text WHERE slots.slot_revision_id=page.page_latest AND content.content_id=slots.slot_content_id AND text.old_id=REPLACE(content.content_address, 'tt:', '')