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#pragma once
#include <Core/Block.h>
#include <Interpreters/Context_fwd.h>
#include <Interpreters/InDepthNodeVisitor.h>
#include <Common/typeid_cast.h>
namespace DB
{
class ASTSubquery;
class ASTFunction;
struct ASTTableExpression;
/** Replace subqueries that return exactly one row
* ("scalar" subqueries) to the corresponding constants.
*
* If the subquery returns more than one column, it is replaced by a tuple of constants.
*
* Features
*
* A replacement occurs during query analysis, and not during the main runtime, so
* the query result can be used for the index in the table.
*
* Scalar subqueries are executed on the request-initializer server.
* The request is sent to remote servers with already substituted constants.
*/
class ExecuteScalarSubqueriesMatcher
{
public:
using Visitor = InDepthNodeVisitor<ExecuteScalarSubqueriesMatcher, true>;
struct Data : public WithContext
{
size_t subquery_depth;
Scalars & scalars;
Scalars & local_scalars;
bool only_analyze;
bool is_create_parameterized_view;
bool replace_only_to_literals;
std::optional<size_t> max_literal_size;
};
static bool needChildVisit(ASTPtr & node, const ASTPtr &);
static void visit(ASTPtr & ast, Data & data);
private:
static void visit(const ASTSubquery & subquery, ASTPtr & ast, Data & data);
static void visit(const ASTFunction & func, ASTPtr & ast, Data & data);
};
using ExecuteScalarSubqueriesVisitor = ExecuteScalarSubqueriesMatcher::Visitor;
bool worthConvertingScalarToLiteral(const Block & scalar, std::optional<size_t> max_literal_size);
}
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