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Sergei Petrunia
2014-11-20 21:09:57 +03:00
parent be1c17669c
commit 1f3724a583
2 changed files with 24 additions and 0 deletions
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18
sql/sql_select.cc
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@ -20736,6 +20736,24 @@ static void free_blobs(Field **ptr)
}
/*
@brief
Remove duplicates from a temporary table.
@detail
Remove duplicate rows from a temporary table. This is used for e.g. queries
like
select distinct count(*) as CNT from tbl group by col
Here, we get a group table with count(*) values. It is not possible to
prevent duplicates from appearing in the table (as we don't know the values
before we've done the grouping). Because of that, we have this function to
scan the temptable (maybe, multiple times) and remove the duplicate rows
Rows that do not satisfy 'having' condition are also removed.
*/
static int
remove_duplicates(JOIN *join, TABLE *table, List<Item> &fields, Item *having)
{