comment made more explanatory

de3019c6 · kostja@oak.local · 29eec6c7 · de3019c6
Commit de3019c6 authored Sep 16, 2003 by kostja@oak.local
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Showing with 7 additions and 5 deletions

sql/sql_select.cc sql/sql_select.cc +7 -5

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--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -2149,11 +2149,13 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
        }
        /*
-          In case of full scan we check every row in the table: 
+          We estimate the cost of making full cortesian product between
-          here we take into account rows read and skipped, as well as rows
+          rows in the scanned table and generated records as
-          passed to next select
+          record_count*s->records/TIME_FOR_COMPARE. Taking into account
+          cost of evaluating WHERE clause for s->found_records is not
+          necessary because it costs much less than the cost mentioned
+          above.
        */
 	if (best == DBL_MAX ||
 	    (tmp  + record_count/(double) TIME_FOR_COMPARE*s->records <
 	     best + record_count/(double) TIME_FOR_COMPARE*records))