Merge pull request #35706 from yakov-olkhovskiy/ephemeral-35641

Allow EPHEMERAL without explicit default expression

docs/en/sql-reference/statements/create/table.md

@@ -114,9 +114,9 @@ In addition, this column is not substituted when using an asterisk in a SELECT q
 
 ### EPHEMERAL {#ephemeral}
 
-`EPHEMERAL expr`
+`EPHEMERAL [expr]`
 
-Ephemeral column. Such a column isn't stored in the table and cannot be SELECTed, but can be referenced in the defaults of CREATE statement.
+Ephemeral column. Such a column isn't stored in the table and cannot be SELECTed, but can be referenced in the defaults of CREATE statement. If `expr` is omitted type for column is required.
 INSERT without list of columns will skip such column, so SELECT/INSERT invariant is preserved -  the dump obtained using `SELECT *` can be inserted back into the table using INSERT without specifying the list of columns.
 
 ### ALIAS {#alias}

docs/ru/sql-reference/statements/create/table.md

@@ -110,9 +110,9 @@ SELECT x, toTypeName(x) FROM t1;
 
 ### EPHEMERAL {#ephemeral}
 
-`EPHEMERAL expr`
+`EPHEMERAL [expr]`
 
-Эфемерное выражение. Такой столбец не хранится в таблице и не может быть получен в запросе SELECT, но на него можно ссылаться в выражениях по умолчанию запроса CREATE.
+Эфемерное выражение. Такой столбец не хранится в таблице и не может быть получен в запросе SELECT, но на него можно ссылаться в выражениях по умолчанию запроса CREATE. Если значение по умолчанию `expr` не указано, то тип колонки должен быть специфицирован.
 INSERT без списка столбцов игнорирует этот столбец, таким образом сохраняется инвариант - т.е. дамп, полученный путём `SELECT *`, можно вставить обратно в таблицу INSERT-ом без указания списка столбцов.
 
 ### ALIAS {#alias}

src/Interpreters/InterpreterCreateQuery.cpp

@@ -508,7 +508,9 @@ ColumnsDescription InterpreterCreateQuery::getColumnsDescription(
 
                 default_expr_list->children.emplace_back(
                     setAlias(
-                        col_decl.default_expression->clone(),
+                        col_decl.default_specifier == "EPHEMERAL" ? /// can be ASTLiteral::value NULL
+                            std::make_shared<ASTLiteral>(data_type_ptr->getDefault()) :
+                            col_decl.default_expression->clone(),
                         tmp_column_name));
             }
             else
@@ -536,7 +538,11 @@ ColumnsDescription InterpreterCreateQuery::getColumnsDescription(
 
         if (col_decl.default_expression)
         {
-            ASTPtr default_expr = col_decl.default_expression->clone();
+            ASTPtr default_expr =
+                col_decl.default_specifier == "EPHEMERAL" && col_decl.default_expression->as<ASTLiteral>()->value.isNull() ?
+                    std::make_shared<ASTLiteral>(DataTypeFactory::instance().get(col_decl.type)->getDefault()) :
+                    col_decl.default_expression->clone();
+
             if (col_decl.type)
                 column.type = name_type_it->type;
             else

src/Parsers/ASTColumnDeclaration.cpp

@@ -1,6 +1,7 @@
 #include <Parsers/ASTColumnDeclaration.h>
 #include <Common/quoteString.h>
 #include <IO/Operators.h>
+#include <Parsers/ASTLiteral.h>
 
 
 namespace DB
@@ -71,8 +72,12 @@ void ASTColumnDeclaration::formatImpl(const FormatSettings & settings, FormatSta
 
     if (default_expression)
     {
-        settings.ostr << ' ' << (settings.hilite ? hilite_keyword : "") << default_specifier << (settings.hilite ? hilite_none : "") << ' ';
+        settings.ostr << ' ' << (settings.hilite ? hilite_keyword : "") << default_specifier << (settings.hilite ? hilite_none : "");
-        default_expression->formatImpl(settings, state, frame);
+        if (default_specifier != "EPHEMERAL" || !default_expression->as<ASTLiteral>()->value.isNull())
+        {
+            settings.ostr << ' ';
+            default_expression->formatImpl(settings, state, frame);
+        }
     }
 
     if (comment)

src/Parsers/ParserCreateQuery.h

@@ -9,6 +9,7 @@
 #include <Parsers/CommonParsers.h>
 #include <Parsers/ParserDataType.h>
 #include <Poco/String.h>
+#include <Parsers/ASTLiteral.h>
 
 
 namespace DB
@@ -185,8 +186,7 @@ bool IParserColumnDeclaration<NameParser>::parseImpl(Pos & pos, ASTPtr & node, E
     }
 
     Pos pos_before_specifier = pos;
-    if (s_default.ignore(pos, expected) || s_materialized.ignore(pos, expected) ||
+    if (s_default.ignore(pos, expected) || s_materialized.ignore(pos, expected) || s_alias.ignore(pos, expected))
-        s_ephemeral.ignore(pos, expected) || s_alias.ignore(pos, expected))
     {
         default_specifier = Poco::toUpper(std::string{pos_before_specifier->begin, pos_before_specifier->end});
 
@@ -194,6 +194,12 @@ bool IParserColumnDeclaration<NameParser>::parseImpl(Pos & pos, ASTPtr & node, E
         if (!expr_parser.parse(pos, default_expression, expected))
             return false;
     }
+    else if (s_ephemeral.ignore(pos, expected))
+    {
+        default_specifier = "EPHEMERAL";
+        if (!expr_parser.parse(pos, default_expression, expected) && type)
+            default_expression = std::make_shared<ASTLiteral>(Field());
+    }
 
     if (require_type && !type && !default_expression)
         return false; /// reject column name without type

tests/queries/0_stateless/02205_ephemeral_1.reference

@@ -6,3 +6,11 @@ z	UInt32	DEFAULT	5
 17	5
 7	5
 21	5
+x	UInt32	DEFAULT	y			
+y	UInt32	EPHEMERAL	0			
+z	UInt32	DEFAULT	5			
+1	2
+0	2
+0	5
+7	5
+21	5

tests/queries/0_stateless/02205_ephemeral_1.sql

@@ -38,3 +38,43 @@ SELECT * FROM t_ephemeral_02205_1;
 
 
 DROP TABLE IF EXISTS t_ephemeral_02205_1;
+
+# Test without default
+CREATE TABLE t_ephemeral_02205_1 (x UInt32 DEFAULT y, y UInt32 EPHEMERAL, z UInt32 DEFAULT 5) ENGINE = Memory;
+
+DESCRIBE t_ephemeral_02205_1;
+
+# Test INSERT without columns list - should participate only ordinary columns (x, z)
+INSERT INTO t_ephemeral_02205_1 VALUES (1, 2);
+# SELECT * should only return ordinary columns (x, z) - ephemeral is not stored in the table
+SELECT * FROM t_ephemeral_02205_1;
+
+TRUNCATE TABLE t_ephemeral_02205_1;
+
+INSERT INTO t_ephemeral_02205_1 VALUES (DEFAULT, 2);
+SELECT * FROM t_ephemeral_02205_1;
+
+TRUNCATE TABLE t_ephemeral_02205_1;
+
+# Test INSERT using ephemerals default
+INSERT INTO t_ephemeral_02205_1 (x, y) VALUES (DEFAULT, DEFAULT);
+SELECT * FROM t_ephemeral_02205_1;
+
+TRUNCATE TABLE t_ephemeral_02205_1;
+
+# Test INSERT using explicit ephemerals value
+INSERT INTO t_ephemeral_02205_1 (x, y) VALUES (DEFAULT, 7);
+SELECT * FROM t_ephemeral_02205_1;
+
+# Test ALTER TABLE DELETE
+ALTER TABLE t_ephemeral_02205_1 DELETE WHERE x = 7;
+SELECT * FROM t_ephemeral_02205_1;
+
+TRUNCATE TABLE t_ephemeral_02205_1;
+
+# Test INSERT into column, defaulted to ephemeral, but explicitly provided with value
+INSERT INTO t_ephemeral_02205_1 (x, y) VALUES (21, 7);
+SELECT * FROM t_ephemeral_02205_1;
+
+DROP TABLE IF EXISTS t_ephemeral_02205_1;
+