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dbms: development [#CONV-2944].

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Alexey Milovidov 2011-09-25 06:42:59 +00:00
parent 3934964e44
commit 6cccbca00a
1 changed files with 3 additions and 3 deletions
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6
dbms/src/Interpreters/InterpreterSelectQuery.cpp
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@ -93,14 +93,14 @@ BlockInputStreamPtr InterpreterSelectQuery::execute()
limit_offset = boost::get<UInt64>(dynamic_cast<ASTLiteral &>(*query.limit_offset).value);
}
bool has_aggregates = expression->hasAggregates();
bool need_aggregate = expression->hasAggregates() || query.group_expression_list;
/** Оптимизация - если не указаны WHERE, GROUP, HAVING, ORDER, но указан LIMIT, и limit + offset < max_block_size,
* то в качестве размера блока будем использовать limit + offset (чтобы не читать из таблицы больше, чем запрошено).
*/
size_t block_size = max_block_size;
if (!query.where_expression && !query.group_expression_list && !query.having_expression && !query.order_expression_list
&& query.limit_length && !has_aggregates && limit_length + limit_offset < block_size)
&& query.limit_length && !need_aggregate && limit_length + limit_offset < block_size)
{
block_size = limit_length + limit_offset;
}
@ -123,7 +123,7 @@ BlockInputStreamPtr InterpreterSelectQuery::execute()
}
/// Если есть GROUP BY - сначала выполним часть выражения, необходимую для его вычисления
if (has_aggregates)
if (need_aggregate)
{
expression->markBeforeAndAfterAggregation(PART_BEFORE_AGGREGATING, PART_AFTER_AGGREGATING);