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Take into account that table scans may use indexes

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monty@hundin.mysql.fi
2002-01-30 16:07:11 +02:00
parent 869b7914be
commit c396824b2a
5 changed files with 22 additions and 7 deletions
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9
sql/sql_select.cc
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@@ -1939,10 +1939,17 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
/*
Don't test table scan if it can't be better.
Prefer key lookup if we would use the same key for scanning.
Don't do a table scan on InnoDB tables, if we can read the used
parts of the row from any of the used index.
This is because table scans uses index and we would not win
anything by using a table scan.
*/
if ((records >= s->found_records || best > s->read_time) &&
!(s->quick && best_key && s->quick->index == best_key->key &&
best_max_key_part >= s->table->quick_key_parts[best_key->key]))
best_max_key_part >= s->table->quick_key_parts[best_key->key]) &&
!((s->table->file->option_flag() & HA_TABLE_SCAN_ON_INDEX) &&
s->table->used_keys && best_key))
{ // Check full join
if (s->on_expr)
{