PS-10232 [8.0]: MySQL 8.0.40+ is about 2-3x times slower than 8.0.39 in particular index scan scenario #5783
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particular index scan scenario A follow up fix for "Bug#36775910: Record buffer not set in index range scans" [2969af5] caused a performance regression by failing to respect the handler's recommendation to cap the number of rows in the record buffer (at the time of writing hard-coded to 100 for InnoDB). This caused a performance regression which is most pronounced when using a small LIMIT. Fixed by re-introducing the line implementing cap.
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A follow up fix for "Bug#36775910: Record buffer not set in index range scans" [2969af5] caused a performance regression by failing to respect the handler's recommendation to cap the number of rows in the record buffer (at the time of writing hard-coded to 100 for InnoDB). This caused a performance regression which is most pronounced when using a small LIMIT.
Fixed by re-introducing the line implementing cap.