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Fix for division by zero problem:

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* Don't try building ROR-intersect if the queried table has zero rows
 * Don't ever produce an estimate of zero returned rows.
This commit is contained in:
unknown 2004-11-28 21:02:30 +03:00
parent d2c7736c59
commit 46e12a2b48
1 changed files with 8 additions and 2 deletions
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10
sql/opt_range.cc
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@ -2716,7 +2716,7 @@ TRP_ROR_INTERSECT *get_best_ror_intersect(const PARAM *param, SEL_TREE *tree,
double min_cost= read_time;
DBUG_ENTER("get_best_ror_intersect");
if (tree->n_ror_scans < 2)
if ((tree->n_ror_scans < 2) || !param->table->file->records)
DBUG_RETURN(NULL);
/*
@ -2803,6 +2803,9 @@ TRP_ROR_INTERSECT *get_best_ror_intersect(const PARAM *param, SEL_TREE *tree,
min_cost= intersect->total_cost;
best_rows= (ha_rows)(intersect->records_fract*
rows2double(param->table->file->records));
/* Prevent divisons by zero */
if (!best_rows)
best_rows= 1;
is_best_covering= intersect->is_covering;
intersect_scans_best= intersect_scans_end;
best_index_scan_costs= intersect->index_scan_costs;
@ -2847,6 +2850,9 @@ TRP_ROR_INTERSECT *get_best_ror_intersect(const PARAM *param, SEL_TREE *tree,
min_cost= intersect->total_cost;
best_rows= (ha_rows)(intersect->records_fract*
rows2double(param->table->file->records));
/* Prevent divisons by zero */
if (!best_rows)
best_rows= 1;
is_best_covering= intersect->is_covering;
best_index_scan_costs= intersect->index_scan_costs;
}
@ -2866,7 +2872,7 @@ TRP_ROR_INTERSECT *get_best_ror_intersect(const PARAM *param, SEL_TREE *tree,
trp->last_scan= trp->first_scan + best_num;
trp->is_covering= is_best_covering;
trp->read_cost= min_cost;
trp->records= best_rows? best_rows : 1;
trp->records= best_rows;
trp->index_scan_costs= best_index_scan_costs;
trp->cpk_scan= cpk_scan;
DBUG_PRINT("info",