ClickHouse/dbms/Interpreters/QueryNormalizer.h

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#pragma once
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#include <map>
#include <Parsers/IAST.h>
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#include <Interpreters/Aliases.h>
namespace DB
{
class ASTSelectQuery;
class ASTIdentifier;
struct ASTTablesInSelectQueryElement;
class Context;
class QueryNormalizer
{
/// Extracts settings, mostly to show which are used and which are not.
struct ExtractedSettings
{
const UInt64 max_ast_depth;
const UInt64 max_expanded_ast_elements;
template <typename T>
ExtractedSettings(const T & settings)
: max_ast_depth(settings.max_ast_depth),
max_expanded_ast_elements(settings.max_expanded_ast_elements)
{}
};
public:
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struct Data
{
using SetOfASTs = std::set<const IAST *>;
using MapOfASTs = std::map<ASTPtr, ASTPtr>;
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const Aliases & aliases;
const ExtractedSettings settings;
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/// tmp data
size_t level;
MapOfASTs finished_asts; /// already processed vertices (and by what they replaced)
SetOfASTs current_asts; /// vertices in the current call stack of this method
std::string current_alias; /// the alias referencing to the ancestor of ast (the deepest ancestor with aliases)
Data(const Aliases & aliases_, ExtractedSettings && settings_)
: aliases(aliases_)
, settings(settings_)
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, level(0)
{}
};
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QueryNormalizer(Data & data)
: visitor_data(data)
{}
void visit(ASTPtr & ast)
{
visit(ast, visitor_data);
}
private:
Data & visitor_data;
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static void visit(ASTPtr & ast, Data & data);
static void visit(ASTIdentifier &, ASTPtr &, Data &);
static void visit(ASTTablesInSelectQueryElement &, const ASTPtr &, Data &);
static void visit(ASTSelectQuery &, const ASTPtr &, Data &);
static void visitChildren(const ASTPtr &, Data & data);
};
}