dbms: added EXISTS TABLE query [#CONV-2944].

dbms/include/DB/Interpreters/InterpreterExistsQuery.h

@@ -0,0 +1,81 @@
+#pragma once
+
+#include <DB/Storages/IStorage.h>
+#include <DB/Parsers/ASTExistsQuery.h>
+#include <DB/Interpreters/Context.h>
+#include <DB/DataStreams/OneBlockInputStream.h>
+#include <DB/DataStreams/BlockIO.h>
+#include <DB/DataStreams/copyData.h>
+#include <DB/DataTypes/DataTypesNumberFixed.h>
+
+
+namespace DB
+{
+
+
+/** Проверить, существует ли таблица. Вернуть одну строку с одним столбцом result типа UInt8 со значением 0 или 1.
+  */
+class InterpreterExistsQuery
+{
+public:
+	InterpreterExistsQuery(ASTPtr query_ptr_, Context & context_)
+		: query_ptr(query_ptr_), context(context_) {}
+
+	BlockIO execute()
+	{
+		BlockIO res;
+		res.in = executeImpl();
+		res.in_sample = getSampleBlock();
+
+		return res;
+	}
+	
+	BlockInputStreamPtr executeAndFormat(WriteBuffer & buf)
+	{
+		Block sample = getSampleBlock();
+		String format_name = "TabSeparated";
+
+		BlockInputStreamPtr in = executeImpl();
+		BlockOutputStreamPtr out = context.getFormatFactory().getOutput(format_name, buf, sample);
+
+		copyData(*in, *out);
+
+		return in;
+	}
+
+private:
+	ASTPtr query_ptr;
+	Context context;
+
+	Block getSampleBlock()
+	{
+		ColumnWithNameAndType col;
+		col.name = "result";
+		col.type = new DataTypeUInt8;
+
+		Block block;
+		block.insert(col);
+
+		return block;
+	}
+
+	BlockInputStreamPtr executeImpl()
+	{
+		const ASTExistsQuery & ast = dynamic_cast<const ASTExistsQuery &>(*query_ptr);
+
+		bool res = context.isTableExist(ast.database, ast.table);
+		
+		ColumnWithNameAndType col;
+		col.name = "result";
+		col.type = new DataTypeUInt8;
+		col.column = new ColumnConstUInt8(1, res);
+
+		Block block;
+		block.insert(col);
+
+		return new OneBlockInputStream(block);
+	}
+};
+
+
+}

dbms/include/DB/Parsers/ASTExistsQuery.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <DB/Parsers/IAST.h>
+
+
+namespace DB
+{
+
+
+/** EXISTS запрос
+  */
+class ASTExistsQuery : public IAST
+{
+public:
+	String database;
+	String table;
+
+	ASTExistsQuery() {}
+	ASTExistsQuery(StringRange range_) : IAST(range_) {}
+	
+	/** Получить текст, который идентифицирует этот элемент. */
+	String getID() { return "ExistsQuery_" + database + "_" + table; };
+
+	ASTPtr clone() const { return new ASTExistsQuery(*this); }
+};
+
+}

dbms/include/DB/Parsers/ParserExistsQuery.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <DB/Parsers/IParserBase.h>
+#include <DB/Parsers/ExpressionElementParsers.h>
+
+
+namespace DB
+{
+
+/** Запрос EXISTS TABLE [db.]name
+  */
+class ParserExistsQuery : public IParserBase
+{
+protected:
+	String getName() { return "EXISTS query"; }
+	bool parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected);
+};
+
+}

dbms/include/DB/Parsers/formatAST.h

@@ -12,6 +12,7 @@
 #include <DB/Parsers/ASTUseQuery.h>
 #include <DB/Parsers/ASTSetQuery.h>
 #include <DB/Parsers/ASTOptimizeQuery.h>
+#include <DB/Parsers/ASTExistsQuery.h>
 #include <DB/Parsers/ASTExpressionList.h>
 #include <DB/Parsers/ASTFunction.h>
 #include <DB/Parsers/ASTIdentifier.h>
@@ -39,6 +40,7 @@ void formatAST(const ASTShowTablesQuery	& ast, std::ostream & s, size_t indent =
 void formatAST(const ASTUseQuery		& ast, std::ostream & s, size_t indent = 0, bool hilite = true, bool one_line = false);
 void formatAST(const ASTSetQuery		& ast, std::ostream & s, size_t indent = 0, bool hilite = true, bool one_line = false);
 void formatAST(const ASTOptimizeQuery	& ast, std::ostream & s, size_t indent = 0, bool hilite = true, bool one_line = false);
+void formatAST(const ASTExistsQuery		& ast, std::ostream & s, size_t indent = 0, bool hilite = true, bool one_line = false);
 void formatAST(const ASTExpressionList 	& ast, std::ostream & s, size_t indent = 0, bool hilite = true, bool one_line = false);
 void formatAST(const ASTFunction 		& ast, std::ostream & s, size_t indent = 0, bool hilite = true, bool one_line = false);
 void formatAST(const ASTIdentifier 		& ast, std::ostream & s, size_t indent = 0, bool hilite = true, bool one_line = false);

dbms/src/Interpreters/InterpreterQuery.cpp

@@ -7,6 +7,7 @@
 #include <DB/Parsers/ASTUseQuery.h>
 #include <DB/Parsers/ASTSetQuery.h>
 #include <DB/Parsers/ASTOptimizeQuery.h>
+#include <DB/Parsers/ASTExistsQuery.h>
 
 #include <DB/Interpreters/InterpreterSelectQuery.h>
 #include <DB/Interpreters/InterpreterInsertQuery.h>
@@ -17,6 +18,7 @@
 #include <DB/Interpreters/InterpreterUseQuery.h>
 #include <DB/Interpreters/InterpreterSetQuery.h>
 #include <DB/Interpreters/InterpreterOptimizeQuery.h>
+#include <DB/Interpreters/InterpreterExistsQuery.h>
 #include <DB/Interpreters/InterpreterQuery.h>
 
 
@@ -77,6 +79,11 @@ void InterpreterQuery::execute(WriteBuffer & ostr, ReadBuffer * remaining_data_i
 		InterpreterOptimizeQuery interpreter(query_ptr, context);
 		interpreter.execute();
 	}
+	if (dynamic_cast<ASTExistsQuery *>(&*query_ptr))
+	{
+		InterpreterExistsQuery interpreter(query_ptr, context);
+		query_plan = interpreter.executeAndFormat(ostr);
+	}
 	else
 		throw Exception("Unknown type of query: " + query_ptr->getID(), ErrorCodes::UNKNOWN_TYPE_OF_QUERY);
 }
@@ -133,6 +140,11 @@ BlockIO InterpreterQuery::execute()
 		InterpreterOptimizeQuery interpreter(query_ptr, context);
 		interpreter.execute();
 	}
+	else if (dynamic_cast<ASTExistsQuery *>(&*query_ptr))
+	{
+		InterpreterExistsQuery interpreter(query_ptr, context);
+		res = interpreter.execute();
+	}
 	else
 		throw Exception("Unknown type of query: " + query_ptr->getID(), ErrorCodes::UNKNOWN_TYPE_OF_QUERY);
 

dbms/src/Parsers/ParserExistsQuery.cpp

@@ -0,0 +1,65 @@
+#include <DB/Parsers/ASTIdentifier.h>
+#include <DB/Parsers/ASTExistsQuery.h>
+
+#include <DB/Parsers/CommonParsers.h>
+#include <DB/Parsers/ParserExistsQuery.h>
+
+
+namespace DB
+{
+
+
+bool ParserExistsQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected)
+{
+	Pos begin = pos;
+
+	ParserWhiteSpaceOrComments ws;
+	ParserString s_exists("EXISTS", true, true);
+	ParserString s_table("TABLE", true, true);
+	ParserString s_dot(".");
+	ParserIdentifier name_p;
+
+	ASTPtr database;
+	ASTPtr table;
+
+	ws.ignore(pos, end);
+
+	if (!s_exists.ignore(pos, end, expected))
+		return false;
+
+	ws.ignore(pos, end);
+
+	if (!s_table.ignore(pos, end, expected))
+		return false;
+
+	ws.ignore(pos, end);
+
+	if (!name_p.parse(pos, end, table, expected))
+		return false;
+
+	ws.ignore(pos, end);
+
+	if (s_dot.ignore(pos, end, expected))
+	{
+		database = table;
+		if (!name_p.parse(pos, end, table, expected))
+			return false;
+
+		ws.ignore(pos, end);
+	}
+
+	ws.ignore(pos, end);
+
+	ASTExistsQuery * query = new ASTExistsQuery(StringRange(begin, pos));
+	node = query;
+
+	if (database)
+		query->database = dynamic_cast<ASTIdentifier &>(*database).name;
+	if (table)
+		query->table = dynamic_cast<ASTIdentifier &>(*table).name;
+
+	return true;
+}
+
+
+}

dbms/src/Parsers/ParserQuery.cpp

@@ -5,6 +5,7 @@
 #include <DB/Parsers/ParserRenameQuery.h>
 #include <DB/Parsers/ParserShowTablesQuery.h>
 #include <DB/Parsers/ParserOptimizeQuery.h>
+#include <DB/Parsers/ParserExistsQuery.h>
 #include <DB/Parsers/ParserUseQuery.h>
 #include <DB/Parsers/ParserSetQuery.h>
 #include <DB/Parsers/ParserQuery.h>
@@ -25,6 +26,7 @@ bool ParserQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected
 	ParserUseQuery use_p;
 	ParserSetQuery set_p;
 	ParserOptimizeQuery optimize_p;
+	ParserExistsQuery exists_p;
 	
 	bool res = show_tables_p.parse(pos, end, node, expected)
 		|| select_p.parse(pos, end, node, expected)
@@ -34,10 +36,11 @@ bool ParserQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected
 		|| drop_p.parse(pos, end, node, expected)
 		|| use_p.parse(pos, end, node, expected)
 		|| set_p.parse(pos, end, node, expected)
-		|| optimize_p.parse(pos, end, node, expected);
+		|| optimize_p.parse(pos, end, node, expected)
+		|| exists_p.parse(pos, end, node, expected);
 
 	if (!res)
-		expected = "One of: SHOW TABLES, SHOW DATABASES, SELECT, INSERT, CREATE, ATTACH, RENAME, DROP, DETACH, USE, SET, OPTIMIZE";
+		expected = "One of: SHOW TABLES, SHOW DATABASES, SELECT, INSERT, CREATE, ATTACH, RENAME, DROP, DETACH, USE, SET, OPTIMIZE, EXISTS";
 
 	return res;
 }

dbms/src/Parsers/formatAST.cpp

@@ -56,6 +56,7 @@ void formatAST(const IAST & ast, std::ostream & s, size_t indent, bool hilite, b
 	DISPATCH(UseQuery)
 	DISPATCH(SetQuery)
 	DISPATCH(OptimizeQuery)
+	DISPATCH(ExistsQuery)
 	DISPATCH(ExpressionList)
 	DISPATCH(Function)
 	DISPATCH(Identifier)
@@ -224,6 +225,12 @@ void formatAST(const ASTOptimizeQuery		& ast, std::ostream & s, size_t indent, b
 		<< (!ast.database.empty() ? backQuoteIfNeed(ast.database) + "." : "") << backQuoteIfNeed(ast.table);
 }
 
+void formatAST(const ASTExistsQuery			& ast, std::ostream & s, size_t indent, bool hilite, bool one_line)
+{
+	s << (hilite ? hilite_keyword : "") << "EXISTS TABLE " << (hilite ? hilite_none : "")
+		<< (!ast.database.empty() ? backQuoteIfNeed(ast.database) + "." : "") << backQuoteIfNeed(ast.table);
+}
+
 void formatAST(const ASTRenameQuery			& ast, std::ostream & s, size_t indent, bool hilite, bool one_line)
 {
 	s << (hilite ? hilite_keyword : "") << "RENAME TABLE " << (hilite ? hilite_none : "");