ClickHouse/dbms/src/Interpreters/QueryAliasesVisitor.h

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#pragma once
#include <unordered_map>
#include <Interpreters/InDepthNodeVisitor.h>
namespace DB
{
class ASTSelectWithUnionQuery;
class ASTSubquery;
struct ASTTableExpression;
struct ASTArrayJoin;
using Aliases = std::unordered_map<String, ASTPtr>;
/// Visits AST node to collect aliases.
class QueryAliasesMatcher
{
public:
struct Data
{
Aliases & aliases;
};
static constexpr const char * label = "QueryAliases";
static std::vector<ASTPtr *> visit(ASTPtr & ast, Data & data);
static bool needChildVisit(ASTPtr & node, const ASTPtr & child);
private:
static std::vector<ASTPtr *> visit(ASTSubquery & subquery, const ASTPtr & ast, Data & data);
static std::vector<ASTPtr *> visit(const ASTArrayJoin &, const ASTPtr & ast, Data & data);
static void visitOther(const ASTPtr & ast, Data & data);
};
/// Visits AST nodes and collect their aliases in one map (with links to source nodes).
using QueryAliasesVisitor = InDepthNodeVisitor<QueryAliasesMatcher, false>;
}