INSERT BUFFER AND ADAPTIVE HASH INDEX

This section shows the status of these two structures inside InnoDB:

1  -------------------------------------
2  INSERT BUFFER AND ADAPTIVE HASH INDEX
3  -------------------------------------
4  Ibuf for space 0: size 1, free list len 887, seg size 889, is not empty
5  Ibuf for space 0: size 1, free list len 887, seg size 889,
6  2431891 inserts, 2672643 merged recs, 1059730 merges
7  Hash table size 8850487, used cells 2381348, node heap has 4091 buffer(s)
8  2208.17 hash searches/s, 175.05 non-hash searches/s

Line 4 shows information about the insert buffer’s size, the length of its “free list,” and its segment size. The text “for space 0” seems to indicate the possibility of multiple insert buffers—one per tablespace—but that was never implemented, and this text has been removed in more recent MySQL versions. There’s only one insert buffer, so line 5 is really redundant. Line 6 shows statistics about how many buffer operations InnoDB has done. The ratio of merges to inserts gives a good idea of how efficient the buffer is.