Edit 18.5:  verschoben nach
https://forum.fhem.de/index.php/topic,53584.msg1157015.html#msg1157015 (https://forum.fhem.de/index.php/topic,53584.msg1157015.html#msg1157015)
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Edit 11.12.2021  gelöst im Modul DBRep
https://forum.fhem.de/index.php/topic,121043.msg1192670.html#msg1192670
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Hallo
Ich habe angefangen einige Werte in eine Maria-DB zu loggen und dazu auch ältere Werte aus den FileLogs übernommen.
Um die ältere Daten gleich zu reduzieren habe ich jeweils ein "reduceLogNbl 90 average=day include=<device>:<reading>" durchgeführt.
Zunächst dachte ich, dass ich einen Fehler mache. Doch jedesmal wenn ich den Befehl ausgeführt habe ist der letzte Tag unvollständig/unsauber bearbeitet.
Alle Daten (bis auf den letzten Tag) werden sauber auf einen Wert pro Tag mit dem Zeitstempel JJJJ-MM-TT 12:00:00 reduziert (Event = rl_av_d); 
nur beim letzten Tag gibt es eine Mischung aus bearbeiteten und unbearbeiteten Einträgen.
FHEM-Log (dort sieht man für den 30-03 das der letzte Schritt fehlt):
Schritt-1--> 2021.05.11 00:36:45.889 3: DbLog DBLogging: reduceLogNbl deleting 2 records of day: 2021-03-29
Schritt-2--> 2021.05.11 00:36:45.898 3: DbLog DBLogging: reduceLogNbl (hourly-average) updating 2 records of day: 2021-03-29
Schritt-3--> 2021.05.11 00:36:45.911 3: DbLog DBLogging: reduceLogNbl (daily-average) updating 1, deleting 23 records of day: 2021-03-29
Schritt-1--> 2021.05.11 00:36:45.950 3: DbLog DBLogging: reduceLogNbl deleting 7 records of day: 2021-03-30
Schritt-2--> 2021.05.11 00:36:45.966 3: DbLog DBLogging: reduceLogNbl (hourly-average) updating 7 records of day: 2021-03-30
2021.05.11 00:36:45.991 3: DbLog DBLogging: reduceLogNbl finished. Rows processed: 2854, deleted: 2731, updated: 678, time: 7.61sec
Die Datenbankinhalte  sehen wie folgt aus (28. & 29. ok / 30. nok --> 9 records mit Event rl_av_d):
"TIMESTAMP"		"DEVICE""TYPE"		"EVENT"			"READING" "VALUE"	"UNIT"
"2021-03-28 12:00:00"	"Jet"	"HTTPMOD"	"rl_av_d"		"E10"	  "144.291"	"Cent"
"2021-03-29 12:00:00"	"Jet"	"HTTPMOD"	"rl_av_d"		"E10"	  "150.129"	"Cent"
"2021-03-30 00:26:45"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 01:26:46"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 02:26:47"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 03:26:48"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 04:26:48"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 05:26:49"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 06:26:50"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 07:26:51"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 08:26:51"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 09:26:52"	"Jet"	"HTTPMOD"	"E10: 153.9  Cent"	"E10"	  "153.9"	"Cent"
"2021-03-30 10:30:00"	"Jet"	"HTTPMOD"	"rl_av_h"		"E10"	  "149.233"	"Cent"
"2021-03-30 11:30:00"	"Jet"	"HTTPMOD"	"rl_av_h"		"E10"	  "142.900"	"Cent"
"2021-03-30 12:26:55"	"Jet"	"HTTPMOD"	"E10: 144.9  Cent"	"E10"	  "144.9"	"Cent"
"2021-03-30 13:30:00"	"Jet"	"HTTPMOD"	"rl_av_h"		"E10"	  "144.400"	"Cent"
"2021-03-30 14:30:00"	"Jet"	"HTTPMOD"	"rl_av_h"		"E10"	  "141.900"	"Cent"
"2021-03-30 15:26:57"	"Jet"	"HTTPMOD"	"E10: 143.9  Cent"	"E10"	  "143.9"	"Cent"
"2021-03-30 16:30:00"	"Jet"	"HTTPMOD"	"rl_av_h"		"E10"	  "142.900"	"Cent"
"2021-03-30 17:30:00"	"Jet"	"HTTPMOD"	"rl_av_h"		"E10"	  "143.900"	"Cent"
"2021-03-30 18:20:06"	"Jet"	"HTTPMOD"	"E10: 139.9  Cent"	"E10"	  "139.9"	"Cent"
"2021-03-30 19:28:06"	"Jet"	"HTTPMOD"	"E10: 142.9  Cent"	"E10"	  "142.9"	"Cent"
"2021-03-30 19:30:00"	"Jet"	"HTTPMOD"	"rl_av_h"		"E10"	  "141.400"	"Cent"
"2021-03-30 20:24:06"	"Jet"	"HTTPMOD"	"E10: 139.9  Cent"	"E10"	  "139.9"	"Cent"
"2021-03-30 21:24:07"	"Jet"	"HTTPMOD"	"E10: 139.9  Cent"	"E10"	  "139.9"	"Cent"
"2021-03-30 22:24:07"	"Jet"	"HTTPMOD"	"E10: 139.9  Cent"	"E10"	  "139.9"	"Cent"
"2021-03-30 23:24:07"	"Jet"	"HTTPMOD"	"E10: 139.9  Cent"	"E10"	  "139.9"	"Cent"