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dbms: Server: more optimizations. [#METR-14099]

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This commit is contained in:
Alexey Arno 2014-12-25 17:43:53 +03:00
parent 7b32af1024
commit b2485444b4
1 changed files with 48 additions and 35 deletions
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15
dbms/src/Interpreters/InterpreterSelectQuery.cpp
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@ -72,7 +72,11 @@ void InterpreterSelectQuery::basicInit(BlockInputStreamPtr input_, const NamesAn
if (query.table && typeid_cast<ASTSelectQuery *>(&*query.table))
{
if (table_column_names.empty())
context.setColumns(InterpreterSelectQuery(query.table, context, to_stage, subquery_depth).getSampleBlock().getColumnsList());
{
/// Оптимизация: мы считаем, что запрос содержит только один SELECT, даже если это может быть
/// в самом деле цепочка UNION ALL. Первый запрос достаточен для определения нужных столбцов.
context.setColumns(InterpreterSelectQuery(query.table, context, to_stage, subquery_depth, nullptr, false).getSampleBlock().getColumnsList());
}
}
else
{
@ -114,6 +118,8 @@ void InterpreterSelectQuery::basicInit(BlockInputStreamPtr input_, const NamesAn
if (input_)
streams.push_back(input_);
if (isFirstSelectInsideUnionAll())
{
/// Создаем цепочку запросов SELECT и проверяем, что результаты всех запросов SELECT cовместимые.
/// NOTE Мы можем безопасно применить static_cast вместо typeid_cast,
/// потому что знаем, что в цепочке UNION ALL имеются только деревья типа SELECT.
@ -130,6 +136,7 @@ void InterpreterSelectQuery::basicInit(BlockInputStreamPtr input_, const NamesAn
ErrorCodes::UNION_ALL_RESULT_STRUCTURES_MISMATCH);
}
}
}
void InterpreterSelectQuery::initQueryAnalyzer()
{
@ -175,17 +182,20 @@ bool InterpreterSelectQuery::hasAsterisk() const
if (query.hasAsterisk())
return true;
if (isFirstSelectInsideUnionAll())
for (IAST * tree = query.next_union_all.get(); tree != nullptr; tree = static_cast<ASTSelectQuery *>(tree)->next_union_all.get())
{
const auto & next_query = static_cast<ASTSelectQuery &>(*tree);
if (next_query.hasAsterisk())
return true;
}
return false;
}
void InterpreterSelectQuery::renameColumns()
{
if (isFirstSelectInsideUnionAll())
for (IAST * tree = query.next_union_all.get(); tree != nullptr; tree = static_cast<ASTSelectQuery *>(tree)->next_union_all.get())
{
auto & ast = static_cast<ASTSelectQuery &>(*tree);
@ -198,6 +208,7 @@ void InterpreterSelectQuery::rewriteExpressionList(const Names & required_column
if (query.distinct)
return;
if (isFirstSelectInsideUnionAll())
for (IAST* tree = query.next_union_all.get(); tree != nullptr; tree = static_cast<ASTSelectQuery *>(tree)->next_union_all.get())
{
auto & next_query = static_cast<ASTSelectQuery &>(*tree);
@ -206,6 +217,8 @@ void InterpreterSelectQuery::rewriteExpressionList(const Names & required_column
}
query.rewriteSelectExpressionList(required_column_names);
if (isFirstSelectInsideUnionAll())
for (IAST* tree = query.next_union_all.get(); tree != nullptr; tree = static_cast<ASTSelectQuery *>(tree)->next_union_all.get())
{
auto & next_query = static_cast<ASTSelectQuery &>(*tree);