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Fix HAVING without GROUP BY

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This commit is contained in:
Amos Bird 2019-10-27 22:10:54 +08:00
parent f8a401bbf7
commit 77bdfb3350
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GPG Key ID: 80D430DCBECFEDB4
3 changed files with 28 additions and 19 deletions
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45
dbms/src/Interpreters/SyntaxAnalyzer.cpp
View File

@ -266,11 +266,36 @@ const std::unordered_set<String> possibly_injective_function_names
"dictGetDateTime"
};
/** You can not completely remove GROUP BY. Because if there were no aggregate functions, then it turns out that there will be no aggregation.
* Instead, leave `GROUP BY const`.
* Next, see deleting the constants in the analyzeAggregation method.
*/
void appendUnusedGroupByColumn(ASTSelectQuery * select_query, const NameSet & source_columns)
{
/// You must insert a constant that is not the name of the column in the table. Such a case is rare, but it happens.
UInt64 unused_column = 0;
String unused_column_name = toString(unused_column);
while (source_columns.count(unused_column_name))
{
++unused_column;
unused_column_name = toString(unused_column);
}
select_query->setExpression(ASTSelectQuery::Expression::GROUP_BY, std::make_shared<ASTExpressionList>());
select_query->groupBy()->children.emplace_back(std::make_shared<ASTLiteral>(UInt64(unused_column)));
}
/// Eliminates injective function calls and constant expressions from group by statement.
void optimizeGroupBy(ASTSelectQuery * select_query, const NameSet & source_columns, const Context & context)
{
if (!select_query->groupBy())
{
// If there is a HAVING clause without GROUP BY, make sure we have some aggregation happen.
if (select_query->having())
appendUnusedGroupByColumn(select_query, source_columns);
return;
}
const auto is_literal = [] (const ASTPtr & ast) -> bool
{
@ -345,25 +370,7 @@ void optimizeGroupBy(ASTSelectQuery * select_query, const NameSet & source_colum
}
if (group_exprs.empty())
{
/** You can not completely remove GROUP BY. Because if there were no aggregate functions, then it turns out that there will be no aggregation.
* Instead, leave `GROUP BY const`.
* Next, see deleting the constants in the analyzeAggregation method.
*/
/// You must insert a constant that is not the name of the column in the table. Such a case is rare, but it happens.
UInt64 unused_column = 0;
String unused_column_name = toString(unused_column);
while (source_columns.count(unused_column_name))
{
++unused_column;
unused_column_name = toString(unused_column);
}
select_query->setExpression(ASTSelectQuery::Expression::GROUP_BY, std::make_shared<ASTExpressionList>());
select_query->groupBy()->children.emplace_back(std::make_shared<ASTLiteral>(UInt64(unused_column)));
}
appendUnusedGroupByColumn(select_query, source_columns);
}
/// Remove duplicate items from ORDER BY.

1
dbms/tests/queries/0_stateless/01020_having_without_group_by.reference Normal file
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@ -0,0 +1 @@
1

1
dbms/tests/queries/0_stateless/01020_having_without_group_by.sql Normal file
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@ -0,0 +1 @@
SELECT 1 HAVING 1;