PS-10232 [8.0]: Fix performance regression by limiting rows_in_buffer to query LIMIT
#5775
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…r` to query `LIMIT` A follow up fix (2969af5) for "Bug#36775910: Record buffer not set in index range scans" caused a performance regression by failing to respect the handler's recommendation to cap on 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 cap. Future work: It would likely be beneficial to communicate the LIMIT value to the executor so that it could reduce the buffer size accordingly - or not allocate a buffer at all in case of LIMIT 1.
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A follow up fix (2969af5) for "Bug#36775910: Record buffer not set in index range scans" caused a performance regression by failing to respect the handler's recommendation to cap on 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 cap.
Future work: As a future optimization, it would likely be beneficial to communicate the LIMIT value to the executor so that it could reduce the buffer size to that value - or not allocate a buffer at all in case of LIMIT 1.