why there is no index on "fieldlayoutitem.fieldlayout"

[Neo]

Query, Full Table Scan, Executed (#), Errors (#), Warnings (#), Total Time, Maximum Time, Avg Time, Rows Sent (#), Avg. Rows Sent (#), Rows Scanned (#), Avg. Rows Scanned (#), Digest

SELECT `ID` , `FIELDLAYOUT` , `FIELDIDENTIFIER` , `DESCRIPTION` , `VERTICALPOSITION` , `ISHIDDEN` , `ISREQUIRED` , `RENDERERTYPE` FROM `fieldlayoutitem` WHERE `FIELDLAYOUT` = ? , *, 55680, 0, 0, 212923762080.61, 48154980.53, 3824061.76, 20925686, 376.0, 4059382504, 72906.0, 4344d5f10990681d901d647def1e769d

• why there is no index on fieldlayoutitem.fieldlayout when there is a frequent query for this;  this records very frequently with long execution times (as in "thousands of queries per day with average execution time of 3.8 seconds, likely because of the missing index, which results in full table scans for these queries, which probably slows down rendering of pages")

[Neo]

oh, This case can not reproduce in my new MySQL DB. Please close it.