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'conc_sys' test Concurrent execution of SELECT involing at least two INFORMATION_SCHEMA tables, DROP DATABASE statement and DROP TABLE statement could have resulted in stalled connection for this SELECT statement. The problem was that for the first query of a join there was a race between select from I_S.TABLES and DROP DATABASE, and the error (no such database) was prepared to be send to the client, but the join processing was continued. On second query to I_S.COLUMNS there was a race with DROP TABLE, but this error (no such table) was downgraded to warning, and thd->net.report_error was reset. And so neither result nor error was sent to the client. The solution is to stop join processing once it is clear we are going to report a error, and also to downgrade to warnings file system errors like 'no such database' (unless we are in the 'SHOW' command), because I_S is designed not to use locks and the query to I_S should not abort if something is dropped in the middle. No test case is provided since this bug is a result of a race, and is timing dependant. But we test that plain SHOW TABLES and SHOW COLUMNS give a error if there is no such database or a table respectively. mysql-test/r/show_check.result: Add result for the test that SHOW TABLES and SHOW COLUMNS give a error if there is no such database or a table respectively. mysql-test/t/show_check.test: Add test case that SHOW TABLES and SHOW COLUMNS give a error if there is no such database or a table respectively. sql/mysql_priv.h: Remove prototype of mysql_find_files(), which is made static under find_files() name. sql/sql_show.cc: Rename mysql_find_files() to find_files() and make it static. Return FIND_FILES_OK for success, FIND_FILES_OOM for out of memory, and FIND_FILES_DIR for directory reading error. Downgrade error to warning in get_all_tables() if it is a FIND_FILES_DIR error, and we are not in the 'SHOW' command. Once 'result' is set to 1 in get_schema_tables_result(), there's no need in continuing iterations, as we are about to return a error.
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