StoragePtr TableFunctionMerge::execute(const ASTPtr & ast_function, const Context & context) const
{
ASTs & args_func = typeid_cast<ASTFunction &>(*ast_function).children;
if (args_func.size() != 1)
throw Exception("Table function 'merge' requires exactly 2 arguments"
" - name of source database and regexp for table names.",
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
ASTs & args = typeid_cast<ASTExpressionList &>(*args_func.at(0)).children;
if (args.size() != 2)
throw Exception("Table function 'merge' requires exactly 2 arguments"
" - name of source database and regexp for table names.",
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
args[0] = evaluateConstantExpressionOrIdentidierAsLiteral(args[0], context);
args[1] = evaluateConstantExpressionAsLiteral(args[1], context);
String source_database = static_cast<const ASTLiteral &>(*args[0]).value.safeGet<String>();
String table_name_regexp = static_cast<const ASTLiteral &>(*args[1]).value.safeGet<String>();
auto res = StorageMerge::create(
getName(),
std::make_shared<NamesAndTypesList>(chooseColumns(source_database, table_name_regexp, context)),
source_database,
table_name_regexp,
context);
res->startup();
return res;
}
void registerStorageMerge(StorageFactory & factory)
{
factory.registerStorage("Merge", [](const StorageFactory::Arguments & args)
{
/** In query, the name of database is specified as table engine argument which contains source tables,
* as well as regex for source-table names.
*/
ASTs & engine_args = args.engine_args;
if (engine_args.size() != 2)
throw Exception("Storage Merge requires exactly 2 parameters"
" - name of source database and regexp for table names.",
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
engine_args[0] = evaluateConstantExpressionOrIdentifierAsLiteral(engine_args[0], args.local_context);
engine_args[1] = evaluateConstantExpressionAsLiteral(engine_args[1], args.local_context);
String source_database = static_cast<const ASTLiteral &>(*engine_args[0]).value.safeGet<String>();
String table_name_regexp = static_cast<const ASTLiteral &>(*engine_args[1]).value.safeGet<String>();
return StorageMerge::create(
args.table_name, args.columns,
source_database, table_name_regexp, args.context);
});
}