fix and add test

src/Storages/StorageMerge.cpp

@@ -103,9 +103,13 @@ StorageMerge::StorageMerge(
     const StorageID & table_id_,
     const ColumnsDescription & columns_,
     const String & comment,
+    const String & source_database_regexp_,
     const std::unordered_map<String, std::unordered_set<String>> & source_databases_and_tables_,
     ContextPtr context_)
-    : IStorage(table_id_), WithContext(context_->getGlobalContext()), source_databases_and_tables(source_databases_and_tables_)
+    : IStorage(table_id_)
+    , WithContext(context_->getGlobalContext())
+    , source_database_regexp(source_database_regexp_)
+    , source_databases_and_tables(source_databases_and_tables_)
 {
     StorageInMemoryMetadata storage_metadata;
     storage_metadata.setColumns(columns_);
@@ -684,6 +688,10 @@ void registerStorageMerge(StorageFactory & factory)
         String source_database_regexp = engine_args[0]->as<ASTLiteral &>().value.safeGet<String>();
         String table_name_regexp = engine_args[1]->as<ASTLiteral &>().value.safeGet<String>();
 
+        /// If database argument is not String literal, we should not treat it as regexp
+        if (!engine_args[0]->as<ASTLiteral>())
+            source_database_regexp = "^" + source_database_regexp + "$";
+
         return StorageMerge::create(
             args.table_id, args.columns, args.comment, source_database_regexp, table_name_regexp, args.getContext());
     });

src/Storages/StorageMerge.h

@@ -74,6 +74,7 @@ protected:
         const StorageID & table_id_,
         const ColumnsDescription & columns_,
         const String & comment,
+        const String & source_database_regexp_,
         const std::unordered_map<String, std::unordered_set<String>> & source_databases_and_tables_,
         ContextPtr context_);
 

src/TableFunctions/TableFunctionMerge.cpp

@@ -49,11 +49,15 @@ void TableFunctionMerge::parseArguments(const ASTPtr & ast_function, ContextPtr
             " - name of source database and regexp for table names.",
             ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
 
-    args[0] = evaluateConstantExpressionForDatabaseName(args[0], context);
+    auto db_arg = evaluateConstantExpressionForDatabaseName(args[0], context);
-    args[1] = evaluateConstantExpressionAsLiteral(args[1], context);
+    auto table_arg = evaluateConstantExpressionAsLiteral(args[1], context);
 
-    source_database_regexp = args[0]->as<ASTLiteral &>().value.safeGet<String>();
+    source_database_regexp = db_arg->as<ASTLiteral &>().value.safeGet<String>();
-    source_table_regexp = args[1]->as<ASTLiteral &>().value.safeGet<String>();
+    source_table_regexp = table_arg->as<ASTLiteral &>().value.safeGet<String>();
+
+    /// If database argument is not String literal, we should not treat it as regexp
+    if (!args[0]->as<ASTLiteral>())
+        source_database_regexp = "^" + source_database_regexp + "$";
 }
 
 
@@ -122,6 +126,7 @@ StoragePtr TableFunctionMerge::executeImpl(const ASTPtr & /*ast_function*/, Cont
         StorageID(getDatabaseName(), table_name),
         getActualTableStructure(context),
         String{},
+        source_database_regexp,
         getSourceDatabasesAndTables(context),
         context);
 

tests/queries/0_stateless/01902_table_function_merge_db_repr.reference

@@ -0,0 +1,146 @@
+CREATE TABLE t_merge as db.t ENGINE=Merge(^db, ^t)
+SELECT _database, _table, n FROM db.t_merge ORDER BY _database, _table, n
+db	t	0
+db	t	1
+db	t	2
+db	t	3
+db	t	4
+db	t	5
+db	t	6
+db	t	7
+db	t	8
+db	t	9
+db1	t1	0
+db1	t1	1
+db1	t1	2
+db1	t1	3
+db1	t1	4
+db1	t1	5
+db1	t1	6
+db1	t1	7
+db1	t1	8
+db1	t1	9
+db2	t2	0
+db2	t2	1
+db2	t2	2
+db2	t2	3
+db2	t2	4
+db2	t2	5
+db2	t2	6
+db2	t2	7
+db2	t2	8
+db2	t2	9
+db3	t3	0
+db3	t3	1
+db3	t3	2
+db3	t3	3
+db3	t3	4
+db3	t3	5
+db3	t3	6
+db3	t3	7
+db3	t3	8
+db3	t3	9
+SELECT _database, _table, n FROM merge(^db, ^t) ORDER BY _database, _table, n
+db	t	0
+db	t	1
+db	t	2
+db	t	3
+db	t	4
+db	t	5
+db	t	6
+db	t	7
+db	t	8
+db	t	9
+db	t_merge	0
+db	t_merge	0
+db	t_merge	0
+db	t_merge	0
+db	t_merge	1
+db	t_merge	1
+db	t_merge	1
+db	t_merge	1
+db	t_merge	2
+db	t_merge	2
+db	t_merge	2
+db	t_merge	2
+db	t_merge	3
+db	t_merge	3
+db	t_merge	3
+db	t_merge	3
+db	t_merge	4
+db	t_merge	4
+db	t_merge	4
+db	t_merge	4
+db	t_merge	5
+db	t_merge	5
+db	t_merge	5
+db	t_merge	5
+db	t_merge	6
+db	t_merge	6
+db	t_merge	6
+db	t_merge	6
+db	t_merge	7
+db	t_merge	7
+db	t_merge	7
+db	t_merge	7
+db	t_merge	8
+db	t_merge	8
+db	t_merge	8
+db	t_merge	8
+db	t_merge	9
+db	t_merge	9
+db	t_merge	9
+db	t_merge	9
+db1	t1	0
+db1	t1	1
+db1	t1	2
+db1	t1	3
+db1	t1	4
+db1	t1	5
+db1	t1	6
+db1	t1	7
+db1	t1	8
+db1	t1	9
+db2	t2	0
+db2	t2	1
+db2	t2	2
+db2	t2	3
+db2	t2	4
+db2	t2	5
+db2	t2	6
+db2	t2	7
+db2	t2	8
+db2	t2	9
+db3	t3	0
+db3	t3	1
+db3	t3	2
+db3	t3	3
+db3	t3	4
+db3	t3	5
+db3	t3	6
+db3	t3	7
+db3	t3	8
+db3	t3	9
+CREATE TABLE t_merge_1 as db.t ENGINE=Merge(currentDatabase(), ^t)
+SELECT _database, _table, n FROM db.t_merge_1 ORDER BY _database, _table, n
+db1	t1	0
+db1	t1	1
+db1	t1	2
+db1	t1	3
+db1	t1	4
+db1	t1	5
+db1	t1	6
+db1	t1	7
+db1	t1	8
+db1	t1	9
+SELECT _database, _table, n FROM merge(currentDatabase(), ^t) ORDER BY _database, _table, n
+db1	t1	0
+db1	t1	1
+db1	t1	2
+db1	t1	3
+db1	t1	4
+db1	t1	5
+db1	t1	6
+db1	t1	7
+db1	t1	8
+db1	t1	9

tests/queries/0_stateless/01902_table_function_merge_db_repr.sql

@@ -0,0 +1,46 @@
+DROP DATABASE IF EXISTS db;
+DROP DATABASE IF EXISTS db1;
+DROP DATABASE IF EXISTS db2;
+DROP DATABASE IF EXISTS db3;
+
+CREATE DATABASE db;
+CREATE DATABASE db1;
+CREATE DATABASE db2;
+CREATE DATABASE db3;
+
+CREATE TABLE db.t   (n Int8) ENGINE=MergeTree ORDER BY n;
+CREATE TABLE db1.t1 (n Int8) ENGINE=MergeTree ORDER BY n;
+CREATE TABLE db2.t2 (n Int8) ENGINE=MergeTree ORDER BY n;
+CREATE TABLE db3.t3 (n Int8) ENGINE=MergeTree ORDER BY n;
+
+INSERT INTO db.t   SELECT * FROM numbers(10);
+INSERT INTO db1.t1 SELECT * FROM numbers(10);
+INSERT INTO db2.t2 SELECT * FROM numbers(10);
+INSERT INTO db3.t3 SELECT * FROM numbers(10);
+
+SELECT 'CREATE TABLE t_merge as db.t ENGINE=Merge(^db, ^t)';
+CREATE TABLE db.t_merge as db.t ENGINE=Merge('^db', '^t');
+
+SELECT 'SELECT _database, _table, n FROM db.t_merge ORDER BY _database, _table, n';
+SELECT _database, _table, n FROM db.t_merge ORDER BY _database, _table, n;
+
+SELECT 'SELECT _database, _table, n FROM merge(^db, ^t) ORDER BY _database, _table, n';
+SELECT _database, _table, n FROM merge('^db', '^t') ORDER BY _database, _table, n;
+
+USE db1;
+
+-- evaluated value of expression should not be treat as repr
+SELECT 'CREATE TABLE t_merge_1 as db.t ENGINE=Merge(currentDatabase(), ^t)';
+CREATE TABLE db.t_merge_1 as db.t ENGINE=Merge(currentDatabase(), '^t');
+
+SELECT 'SELECT _database, _table, n FROM db.t_merge_1 ORDER BY _database, _table, n';
+SELECT _database, _table, n FROM db.t_merge_1 ORDER BY _database, _table, n;
+
+-- evaluated value of expression should not be treat as repr
+SELECT 'SELECT _database, _table, n FROM merge(currentDatabase(), ^t) ORDER BY _database, _table, n';
+SELECT _database, _table, n FROM merge(currentDatabase(), '^t') ORDER BY _database, _table, n;
+
+DROP DATABASE db;
+DROP DATABASE db1;
+DROP DATABASE db2;
+DROP DATABASE db3;