"QUERY PLAN"
"Limit  (cost=1.55..68057.21 rows=2 width=184)"
"  ->  Append  (cost=1.55..68057.21 rows=2 width=184)"
"        ->  Nested Loop Left Join  (cost=1.55..17.64 rows=1 width=161)"
"              Filter: ((c.destfileid IS NULL) OR (conversiondestfile.id IS NOT NULL))"
"              ->  Nested Loop  (cost=0.98..13.09 rows=1 width=161)"
"                    ->  Limit  (cost=0.70..4.76 rows=1 width=2926)"
"                          ->  Index Scan using mdl_file_con_ix on mdl_files  (cost=0.70..10312.51 rows=2536 width=2926)"
"                                Index Cond: ((contenthash)::text = '94f195cd0f77ecd6fb16004dcac7afd4f7a26d6b'::text)"
"                    ->  Index Scan using mdl_fileconv_sou_ix on mdl_file_conversion c  (cost=0.29..8.31 rows=1 width=161)"
"                          Index Cond: (sourcefileid = mdl_files.id)"
"                          Filter: ((targetformat)::text = 'pdf'::text)"
"              ->  Index Only Scan using mdl_file_id_pk on mdl_files conversiondestfile  (cost=0.57..4.54 rows=1 width=8)"
"                    Index Cond: (id = c.destfileid)"
"        ->  Subquery Scan on ""*SELECT* 2""  (cost=1.68..68039.55 rows=1 width=184)"
"              ->  Nested Loop Left Join  (cost=1.68..68039.53 rows=1 width=168)"
"                    Filter: (orphanedconversion.id IS NULL)"
"                    ->  Nested Loop  (cost=1.27..68031.80 rows=1 width=16)"
"                          Join Filter: ((orphanedsourcefile.contenthash)::text = (orphaneddestfile.filename)::text)"
"                          ->  Index Scan using mdl_file_id_pk on mdl_files orphanedsourcefile  (cost=0.57..8.59 rows=1 width=49)"
"                                Index Cond: (id = 356994111)"
"                          ->  Index Scan using mdl_file_comfilconite_ix on mdl_files orphaneddestfile  (cost=0.70..68021.45 rows=141 width=22)"
"                                Index Cond: (((component)::text = 'core'::text) AND ((filearea)::text = 'documentconversion'::text))"
"                                Filter: ((filepath)::text = '/pdf/'::text)"
"                    ->  Index Scan using mdl_fileconv_des_ix on mdl_file_conversion orphanedconversion  (cost=0.41..7.72 rows=1 width=16)"
"                          Index Cond: (destfileid = orphaneddestfile.id)"