Handler_read_first MySQL Haiku

Posted in: Technical Track

I was writing up some notes about a client’s status variables, and I’d had to remind myself of Handler_read_first. Handler_read_first is a counter that increments when the first entry in the index is read, which may indicate that a full index scan is being used.

With this particular client, I ran a SHOW STATUS, waited 100 seconds, and ran it again. Handler_read_first jumped by about 53. So I wrote down in my notes:

first in the index…every other second. Lots of table scans?

As soon as I wrote it down I said, “That’s a haiku!” I counted syllables, and it works, but only if you pronounce “Every” with 3 syllables.

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