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MWL#90: Address review feedback part #6: more clearer code in next_linear_tab() function

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This commit is contained in:
Sergey Petrunya 2011-03-22 13:17:14 +03:00
parent b77e3dc9f4
commit b9d4c69135
1 changed files with 15 additions and 5 deletions
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20
sql/sql_select.cc
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@ -6389,21 +6389,31 @@ JOIN_TAB *first_linear_tab(JOIN *join, bool after_const_tables)
JOIN_TAB *next_linear_tab(JOIN* join, JOIN_TAB* tab, bool include_bush_roots)
{
if (include_bush_roots && tab->bush_children)
{
/* This JOIN_TAB is a SJM nest; Start from first table in nest */
return tab->bush_children->start;
}
DBUG_ASSERT(!tab->last_leaf_in_bush || tab->bush_root_tab);
if (tab->last_leaf_in_bush)
if (tab->bush_root_tab) /* Are we inside an SJM nest */
{
/* Inside SJM nest */
if (!tab->last_leaf_in_bush)
return tab+1; /* Return next in nest */
/* Continue from the sjm on the top level */
tab= tab->bush_root_tab;
}
if (tab->bush_root_tab)
return ++tab;
/* If no more JOIN_TAB's on the top level */
if (++tab == join->join_tab + join->top_jtrange_tables)
return NULL;
if (!include_bush_roots && tab->bush_children)
{
/* This JOIN_TAB is a SJM nest; Start from first table in nest */
tab= tab->bush_children->start;
}
return tab;
}