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btr0cur.c:

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Improve table cardinality estimate if there are big BLOBs


innobase/btr/btr0cur.c:
  Improve table cardinality estimate if there are big BLOBs
This commit is contained in:
unknown 2001-12-11 23:42:31 +02:00
commit 75125cf0e7
1 changed files with 65 additions and 2 deletions
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67
innobase/btr/btr0cur.c
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@ -85,6 +85,15 @@ btr_rec_free_updated_extern_fields(
inherited fields */
mtr_t* mtr); /* in: mini-transaction handle which contains
an X-latch to record page and to the tree */
/***************************************************************
Gets the externally stored size of a record, in units of a database page. */
static
ulint
btr_rec_get_externally_stored_len(
/*==============================*/
/* out: externally stored part, in units of a
database page */
rec_t* rec); /* in: record */
/*==================== B-TREE SEARCH =========================*/
@ -2540,6 +2549,7 @@ btr_estimate_number_of_different_key_vals(
ulint matched_bytes;
ulint* n_diff;
ulint not_empty_flag = 0;
ulint total_external_size = 0;
ulint i;
ulint j;
mtr_t mtr;
@ -2586,10 +2596,15 @@ btr_estimate_number_of_different_key_vals(
for (j = matched_fields + 1; j <= n_cols; j++) {
n_diff[j]++;
}
total_external_size +=
btr_rec_get_externally_stored_len(rec);
rec = page_rec_get_next(rec);
}
total_external_size +=
btr_rec_get_externally_stored_len(rec);
mtr_commit(&mtr);
}
@ -2597,12 +2612,18 @@ btr_estimate_number_of_different_key_vals(
BTR_KEY_VAL_ESTIMATE_N_PAGES leaf pages, we can estimate how many
there will be in index->stat_n_leaf_pages */
/* We must take into account that our sample actually represents
also the pages used for external storage of fields (those pages are
included in index->stat_n_leaf_pages) */
for (j = 0; j <= n_cols; j++) {
index->stat_n_diff_key_vals[j] =
(n_diff[j] * index->stat_n_leaf_pages
+ BTR_KEY_VAL_ESTIMATE_N_PAGES - 1
+ total_external_size
+ not_empty_flag)
/ BTR_KEY_VAL_ESTIMATE_N_PAGES;
/ (BTR_KEY_VAL_ESTIMATE_N_PAGES
+ total_external_size);
}
mem_free(n_diff);
@ -2610,6 +2631,48 @@ btr_estimate_number_of_different_key_vals(
/*================== EXTERNAL STORAGE OF BIG FIELDS ===================*/
/***************************************************************
Gets the externally stored size of a record, in units of a database page. */
static
ulint
btr_rec_get_externally_stored_len(
/*==============================*/
/* out: externally stored part, in units of a
database page */
rec_t* rec) /* in: record */
{
ulint n_fields;
byte* data;
ulint local_len;
ulint extern_len;
ulint total_extern_len = 0;
ulint i;
if (rec_get_data_size(rec) <= REC_1BYTE_OFFS_LIMIT) {
return(0);
}
n_fields = rec_get_n_fields(rec);
for (i = 0; i < n_fields; i++) {
if (rec_get_nth_field_extern_bit(rec, i)) {
data = rec_get_nth_field(rec, i, &local_len);
local_len -= BTR_EXTERN_FIELD_REF_SIZE;
extern_len = mach_read_from_4(data + local_len
+ BTR_EXTERN_LEN + 4);
total_extern_len += ut_calc_align(extern_len,
UNIV_PAGE_SIZE);
}
}
return(total_extern_len / UNIV_PAGE_SIZE);
}
/***********************************************************************
Sets the ownership bit of an externally stored field in a record. */
static