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[No BUG#] end_tab_idx==-1 passed as parameter to JOIN::get_partial_cost_and_fanout()

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- Handle the case when the subquery's join is degenerate and so has zero tables.
This commit is contained in:
Sergey Petrunya 2011-06-10 12:36:06 +04:00
parent 9e3570ea6c
commit 9c11646fcd
1 changed files with 25 additions and 19 deletions
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44
sql/sql_select.cc
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@ -5920,30 +5920,20 @@ greedy_search(JOIN *join,
/**
Calculate a cost of given partial join order in join->positions.
Get cost of execution and fanout produced by selected tables in the join
prefix (where prefix is defined as prefix in depth-first traversal)
@param n_tables[in] # tables in the partial join order after the last
constant table
@param read_time_arg[out] store read time here
@param record_count_arg[out] store record count here
@param end_tab_idx The number of last tab to be taken into
account (in depth-first traversal prefix)
@param filter_map Bitmap of tables whose cost/fanout are to
be taken into account.
@param read_time_arg [out] store read time here
@param record_count_arg [out] store record count here
@note
end_tab==NULL means get full join cost and fanout
When used by semi-join materialization code the idea is that we
detect sj-materialization after we've put all sj-inner tables into
the join prefix.
prefix-tables semi-join-inner-tables tN
^--we're here
and we'll need to get the cost of prefix-tables prefix again.
When used with non-flattened subqueries, the method computes the
total cost of query plan.
@returns
read_time_arg and record_count_arg contain the computed cost.
read_time_arg and record_count_arg contain the computed cost and fanout
*/
void JOIN::get_partial_cost_and_fanout(uint end_tab_idx,
@ -5959,6 +5949,22 @@ void JOIN::get_partial_cost_and_fanout(uint end_tab_idx,
uint i;
uint last_sj_table= MAX_TABLES;
/*
Handle a special case where the join is degenerate, and produces no
records
*/
if (table_count == 0)
{
*read_time_arg= 0.0;
/*
We return 1, because
- it is the pessimistic estimate (there might be grouping)
- it's safer, as we're less likely to hit the edge cases in
calculations.
*/
*record_count_arg=1.0;
}
for (tab= first_depth_first_tab(this), i= const_tables;
tab;
tab= next_depth_first_tab(this, tab), i++)