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btr0cur.c:

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Do not add + 1 to the InnoDB index cardinality estimate if the B-tree just contains one page; the fix made in March 2004 caused InnoDB systematically to overestimate the cardinality of empty or small tables by 1


innobase/btr/btr0cur.c:
  Do not add + 1 to the InnoDB index cardinality estimate if the B-tree just contains one page; the fix made in March 2004 caused InnoDB systematically to overestimate the cardinality of empty or small tables by 1
This commit is contained in:
unknown 2004-07-15 09:08:51 +03:00
parent 5eb3dc3223
commit 9e6f619834
1 changed files with 9 additions and 2 deletions
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11
innobase/btr/btr0cur.c
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@ -2707,8 +2707,11 @@ btr_estimate_number_of_different_key_vals(
rec = page_rec_get_next(rec);
}
if (n_cols == dict_index_get_n_unique_in_tree(index)) {
/* We add one because we know that the first record
/* If there is more than one leaf page in the tree,
we add one because we know that the first record
on the page certainly had a different prefix than the
last record on the previous index page in the
alphabetical order. Before this fix, if there was
@ -2716,7 +2719,11 @@ btr_estimate_number_of_different_key_vals(
algorithm grossly underestimated the number of rows
in the table. */
n_diff[n_cols]++;
if (btr_page_get_prev(page, &mtr) != FIL_NULL
|| btr_page_get_next(page, &mtr) != FIL_NULL) {
n_diff[n_cols]++;
}
}
total_external_size +=