ClickHouse/dbms/include/DB/Analyzers/AnalyzeArrayJoins.h

#pragma once

#include <DB/Parsers/IAST.h>
#include <unordered_map>
#include <vector>


namespace DB
{

class WriteBuffer;
class CollectAliases;
class CollectTables;


/** For every ARRAY JOIN, collect a map:
  *  result alias -> source
  *
  * There could be several variants:
  *
  * SELECT elem FROM t ARRAY JOIN array AS elem			elem -> array
  * SELECT n.elem FROM t ARRAY JOIN nested AS n			n -> nested
  * SELECT array FROM t ARRAY JOIN array				array -> array
  * SELECT nested.elem FROM t ARRAY JOIN nested			nested -> nested
  * SELECT elem FROM t ARRAY JOIN [1, 2, 3] AS elem		elem -> [1, 2, 3]
  */
struct AnalyzeArrayJoins
{
	void process(const ASTPtr & ast);

	struct SourceInfo
	{
		String column_name;
		ASTPtr node;
	};

	using ResultToSource = std::unordered_map<String, SourceInfo>;
	using ArrayJoins = std::vector<ResultToSource>;

	/// Debug output
	void dump(WriteBuffer & out) const;
};

}